REVIEW REPORT

Infant feeding—a scoping review for Nordic Nutrition Recommendations 2023

Agneta Hörnell^1* and Hanna Lagström²

¹Department of Food, Nutrition and Culinary Science, Umeå University, Umeå, Sweden; ²Department of Public Health, University of Turku and Turku University Hospital, Turku, Finland

Abstract

The 2012 edition of the Nordic Nutrition Recommendations (NNR) included recommendations on breastfeeding, based on the most recent guidelines and recommendations from major national food and health authorities and organizations, systematic reviews, and some original research. For NNR 2023, the scope has been expanded and also includes formula feeding and the introduction of solid food. The main focus in this scoping review is on infants aged 0–12 months but also considers parts both before and beyond the first year, as the concept of ‘the first 1000 days’ emphasizes the importance of factors during pregnancy and the first 2 years of life for immediate and later health: physical as well as emotional and mental health. Breastmilk is the natural and sustainable way to feed an infant during the first months of life. Numerous studies have indicated immediate as well as long-term beneficial effects of breastfeeding on health for both the infant and the breastfeeding mother, and from a public health perspective, it is therefore important to protect, support, and promote breastfeeding. For full-term, normal weight infants, breastmilk is sufficient as the only form of nutrition for the first 6 months, except for vitamin D that needs to be given as supplement. The World Health Organization (WHO) and several other authoritative bodies therefore recommend exclusive breastfeeding during the first 6 months. Starting solids at about 6 months is necessary for both nutritional and developmental reasons. According to the European Food Safety Authority (EFSA) and the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN), solid foods are safe to give from 4 months although exclusive breastfeeding until 6 months is the desirable goal. Breastfeeding can continue together with complementary foods as long as it is mutually desired by the mother and child. If breastfeeding is not enough or for some reason discontinued before the infant is 4 months of age, the infant should be fed infant formula, and, when possible, breastfeeding should be continued alongside the formula feeding. If the infant is 4 months or older, starting with solids together with continued breastfeeding and/or formula feeding is an option. Infant formulas have been developed for infants who are not breastfed or do not get enough breastmilk. Home-made formula should not be given.

Keywords: breastmilk; breastfeeding; breastfeeding statistics; Nordic and Baltic countries; infant formula; introduction of solid foods; health effects of infant feeding

 

 

The concept of the first 1000 days emphasizes the importance of factors during pregnancy (1, 2) and the first 2 years of life for immediate and later health: both physical (3) and emotional and mental health (4). These factors include parental environmental factors at conception as well as maternal nutrition during pregnancy and the way an infant is fed and cared for during the first 2 years of life. The concept is important as it guides actions and policies for improving both child and public health (5, 6). From a public health perspective, the World Health Organization (WHO) stresses the importance to protect, support, and promote breastfeeding (7), and breastmilk has even been called ‘personalised medicine for infants’ (3).

After giving birth, most mothers in the Nordic and Baltic countries breastfeed their infants. Most start with exclusive breastfeeding (Box 1), but this declines relatively quickly and less than half of the infants are still exclusively breastfed at 4 months. However, continued breastfeeding is common with about 60–80% still being breastfed at 6 months and about 30–60% at 12 months.

Box 1. Nomenclature used in the scoping review

¹WHO definition used (8). EFSA (9) and ESPGHAN (10) consider complementary feeding as ‘Breastfeeding or infant formula in combination with solid foods’.

Methods

The present scoping review about infant feeding is a revision of the breastfeeding chapter in the Nordic Nutrition Recommendations (NNR) 2012 (11), which built on two systematic reviews focusing on health effects of breastfeeding and introduction of solids (12) and protein intake 0–18 years of age (13). This has been updated and extended with the most recent guidelines and recommendations from major national food and health authorities and results from three de novo systematic reviews performed within the NNR2023 project (14–16). The revision follows the protocol developed within the NNR2023 project (17) (Box 2). The main sources of evidence used in the review follow the eligibility criteria described by Christensen et al. (18).

Box 2. Background papers for Nordic Nutrition Recommendations 2023

The texts about health effects of breastfeeding described in NNR2012 (11) was updated using results from systematic reviews as well as evidence-based guidelines and recommendations; original research was assessed and included as references when needed. In addition to texts about human milk oligosaccharides (abbreviation HMOs used for both naturally occurring in breastmilk and the manufactured HMOs added to formula), formula feeding and complementary feeding were assessed and added as needed.

Breastfeeding

Recommendations related to breastfeeding

Breastmilk is a natural and sustainable part of early infant feeding (19), and the health benefits of breastfeeding for both the child and the breastfeeding mother are well documented (3) (see below).

Exclusive breastfeeding for 6 months has been recommended by the WHO for more than 20 years (7, 20). This is a strong recommendation that applies to all countries and populations regardless of economic status or developmental level. Exclusive breastfeeding entails that the infant is given no food or liquid other than breastmilk but, if necessary, can receive vitamins, minerals, and medications as well. Globally, most official bodies recommend exclusive breastfeeding the first 6 months or has it as a desirable goal (21), including the Nordic countries (11), Europe (22), the United States (23), Canada (24), and Australia (25).

From 6 months of age, the WHO recommends that breastfeeding continues as part of a healthy diversified diet throughout the first 2 years or beyond (7, 26). The wording of the previous Nordic recommendation for total breastfeeding is somewhat different, stating that breastmilk is recommended as part of the diet until 1 year or longer, as mutually desired by mother and child. The proportion of infants in the Nordic and Baltic countries being breastfed for at least 1 year has increased, and the latest statistics show that about 30–60% of 12 months old infants are breastfed (see also section 4.3).

Before the infant is 4 months of age, if breastfeeding is not enough, discontinued for some reason or never started, the infant should be fed infant formula (Table 1). When possible, breastfeeding should be continued alongside the formula feeding. If the infant is 4 months or older, starting with solids together with continued breastfeeding and/or formula feeding is an option.

Table 1. Outline of recommended foods and drinks at different ages

Age of child	Preferred food	Possible food	Required supplements	Comment
0–4 months	Breastmilk	Infant formula	Vitamin D from 1 week of age1,2
4–6 months	Breastmilk	Infant formula Solid foods3	Vitamin D1,2	Honey and nitrate-rich foods should not be given during the first year (see section Introduction of solid foods).
6–12 months	Breastmilk Solid food3 Water	Infant formula Follow-on formula Gruel/cereal-based drinks	Vitamin D1,2	Follow-on formula is on the market, but the WHO/WHA has clearly stated that these are unnecessary products (WHA 39.28).
One-year onwards	Solid food3 Water	Breastmilk Infant formula Follow-on formula Gruel/cereal-based drinks	Vitamin D until (at least) 2 years of age2,4	In Sweden and Finland, gruel/cereal-based drinks are traditionally used but are not necessary parts of children’s diets. A local milk product is used in Iceland composed according to Codex for follow-on formula. Sugary drinks should not be given during the first 2 years. Rice drinks should be avoided during first 6 years.
WHO/WHA = World Health Organisation and World Health Assembly
1Vitamin D should be given to all children from 1 to 2 weeks of age until (at least) 2 years of age (10, 22, 23).
2In Finland, Iceland and Norway, vitamin D supplementation to formula-fed infants depend on amount of formula eaten (27–29).
3Depending on infant age the consistency can vary between purées, semi-solids, and finger foods.
4Children older than 2 years should continue with extra vitamin D if they do not eat fish or enriched foods, if they are not exposed to the sun during summer.

Content of nutrients and other components in breastmilk

Human breastmilk is a multifaceted fluid containing water, protein, lipids, carbohydrates, vitamins, minerals as well as non-nutritive bioactive factors, such as hormones, growth factors, antibodies, HMOs, and bacteria with metabolites (30–33) (Table 2). Breastmilk gives the newborn essential nutrients in an efficiently absorbed combination (34). The contents of human breastmilk differ significantly from the milk from other mammals. When feeding breastmilk is not an option, parents should be given guidance to feed commercial infant formula to their infants.

Table 2. Nutritional content of breastmilk, infant formulas (on average), and cow’s whole milk

Nutrient/100 g1	Breastmilk	Infant formula2	Cow’s milk
Energy, kJ	273	284	265
Energy, kcal	65	68	63
Protein, g	1.3	1.3	3.0
Fat, g	3.5	3.3	3.1
SAFA, g	1.3	1.3	2.2
MUFA, g	1.4	1.4	0.7
PUFA, g	0.6	0.6	< 0.1
LLA, mg	337	519	45
ALA, mg	69	77	12
EPA, mg	4	4	0
DHA, mg	11	7	0
Carbohydrates, g	7.4	7.7	4.8
Lactose, g	7.4	6.7	4.8
1Based on the national Food Composition Database in Finland (https://fineli.fi/fineli/fi/index).
2Ready-To-Feed, average.

The macronutrient content (as percentage of energy, E%) of mature breastmilk from the individual woman is relatively stable for as long as breastfeeding continues, but the content of vitamins and minerals is influenced by the mother’s diet, and the fat composition varies depending on the mother’s diet and weight status (35–37). For example, the levels of long-chain polyunsaturated fatty acids are highly dependent on the mother’s intake of seafood, linoleic and linolenic acids, and dietary supplements (35, 36).

All infants and young children living at northern latitudes need vitamin D supplements. Sun exposure is insufficient to prevent rickets in the Nordic and Baltic countries, and breastmilk does not contain sufficient vitamin D for prevention even if the mother takes vitamin D supplements (38). If not given a vitamin D supplement, there is a rapid decrease in the serum concentration of 25-hydroxyvitamin D during the first weeks of life to the level usually seen in rickets (39). Supplements should be in the form of vitamin D drops or a multivitamin-mineral supplement, and 10 µg (400 IU) per day is recommended from 1 to 2 weeks of age until (at least) 2 years of age as discussed in the scoping review on vitamin D for NNR2023 (40). For infants fed formula during the first year of life, there are special recommendations regarding vitamin D-supplementation in some countries (see section Formula feeding).

The iron in breastmilk is highly bioavailable and easily absorbed by the infant, and when maternal iron status is good and umbilical cord clamping is delayed at birth (38), most full-term newborns have sufficient iron stored in their bodies for about the first 6 months of life. Some infants, for example, prematurely born, born small-for-gestational age, or with high growth velocity, may be at risk for iron deficiency prior to 6 months (9, 10, 25, 41). By age 6 months, most breastfed infants require an external source of iron and complementary foods should include foods with sufficiently high iron content (e.g. meat, egg, whole grain cereals and bread, lentils, beans, and nuts). Formula-fed infants should receive iron-fortified formula in addition to solid foods (10, 42).

Pregnant and breastfeeding mothers who eat a vegan or vegetarian diet should ensure that they have an adequate intake of vitamin B₁₂, vitamin D, iodine, and the omega 3-fatty acid docosahexaenoic acid (DHA), either through supplements or enriched products, in order to avoid risk of deficiency and to ensure optimal intake in the fetus and infant. This would also be advisable for women with a mixed diet who have a low intake of fish and dairy products.

When the breastfed child of a vegan mother is no longer exclusively breastfed, or the mother’s nutritional status is uncertain, the child should receive a supplement containing vitamin B₁₂ and iodine. When the child begins with solid foods, they should also be given DHA in the form of algae oil (vegetarian omega 3). The European Food Safety Authority (EFSA) suggests 100 mg/day as an adequate intake (AI) for children aged between 6 and 24 months and 250 mg from 2 to 18 years (43). See also section Introduction of solid foods; Plant-based diets below.

There are over 200 defined HMOs, that is, oligosaccharides, constituting the third largest component in human milk after lactose and lipids (44, 45). The total amount and composition of HMOs in the milk are unique for each woman and strongly depends on the maternal genetics (44, 46), as well as maternal and child characteristics such as maternal pre-pregnancy body mass index (BMI), gestational age, parity, and infant sex (45). Although HMOs are only minimally digested prebiotics, they have many important health-related biological functions for the infant (33). These include shaping the development of the gut microbiome by promoting the growth of specific microbes, preventing pathogen invasion and attachment, and altering immune cell responses, possibly also in other sites throughout the body and not only in the infant gut. HMOs may thus affect infants’ risks of infections, allergies, and inflammation (33, 47, 48).

Prevalence of breastfeeding in the Nordic countries

The Nordic countries have relatively high breastfeeding rates. After giving birth, virtually all mothers start breastfeeding their infants and in the Nordic countries, 40–50% of infants are exclusively breastfed for 4 months (Table 3). Exclusive breastfeeding rates then declines relatively quickly, but breastfeeding is commonly continued together with the addition of solids and other fluids than breastmilk (i.e. complementary foods; see Box 1). About 60–80% of infants are still breastfed at 6 months and about 30–60% at 12 months. Breastfeeding rates are similar in the Baltic countries, with 50–70% of infants breastfed at 6 months.

Table 3. Breastfeeding statistics in the Nordic and Baltic countries

	Weeks			Months
	1		>2	1		1.5 (6 weeks)		2			3		4			5		6			8	9	12
	Excl	Any	Danish full brf	Excl	Any	Excl	Any	Excl	Danish full brf	Any	Excl	Any	Excl	Danish full brf	Any	Excl	Any	Excl	Danish full brf	Any	Any	Any	Any
Denmark1			85.4						67.0					57.9					13.4
Finland2				58	93			54		88	53	86	50		85	26	88	9		77		75	58
Iceland3	63	82				65	88	62		88	59	80				40	74	20		68	63		39
Norway4,5	87	97		81	93			74					39		82	5		2		78		63	48
Sweden6	71.8	93.2						60.9		82.8			49.9		73.4			11.9		64.8	51.8		30
Estonia7												81.6								68.5
Latvia8						40.0	88.1				29.7	72.4						16.1		53.7			27.4
Lithuania9	91.49											68.410								49.610
1National statistics for children born in 2022 (n = 34 951; 59.3% of birth cohort included in the statistics) (51) Note: Full breastfeeding is in Denmark defined as only breastmilk + allowed water or similar + a maximum of 1 formula meal per week. In Denmark, no ‘exclusive breastfeeding’ is registered (breastmilk as well as vitamins, minerals, and possibly medicines), as this WHO definition is seen as less appropriate for Danish conditions where there are no health risks for the child associated with not being fully breastfed. 2 months data are collected for age >9 weeks and 4 months for >17 weeks.
2Based on survey in 47 municipalities in mainland Finland October 2019, 3418 families participated with children aged 2 weeks to 12 months, response rate 22% (52). Statistics weighted to match cohort born 2018. The figures in the table are based on the previous day’s feeding.
3Based on national statistics for children born in 2021 (n = 4,879). Data from primary health care centers’ regular check-ups in Iceland (53).
4Based on national sample of 3000 children born 1–29 March 2018. Data collection at 6 months of age, included 2182 children (73%) (54). Data collection at 9 and 12 months included 1966 children (66% of those possible to contact) (55).
5Exclusive breastfeeding rate at 5 months was taken at 5.5 months
6Based on national statistics for children born in 2021 (n = 105,549) (56). Data are missing from 6 of 22 regions (=14% of children born 2021), National average is calculated using estimates based on most recent data from these regions (57).
7Based on national statistics for children who became 1 year old during 2022 (n = 13 101) (58).
8Based on national statistics for children born in 2022 (n = 17 494) (59).
9Based on national statistics for children born in 2020 (n = 23,400) (60) (https://www.hi.lt/uploads/pdf/leidiniai/Statistikos/Gimimu/gimimai_2020.pdf).
10Based on national statistics for children born in 2018 (n = 28,149) (61).

When comparing breastfeeding statistics between countries and within a country over time, it is necessary to consider both how exclusive breastfeeding is defined and how data collection is performed, whether data is based on national data or smaller samples but also participation rates. Lack of standardized definitions and data collection methods, as well as absence of agreements about at which ages statistics should be collected, makes comparisons difficult (49, 50). This problem is clearly seen in Table 3 showing the most recent breastfeeding statistics from the Nordic and Baltic countries.

Vaz et al. (50) describe breastfeeding rates and annual change in 51 high-income countries based on nationally representative samples from various sources collected between 1985 and 2019. They looked at indicators related to start of breastfeeding (hours after delivery), proportion ever being breastfed (even of short duration), exclusivity of breastfeeding at different ages, and proportion still being breastfed at 1 and 2 years (including estimates for different ages between 9 and 24 months). Their conclusion was that breastfeeding practices seemed to be improving in most of these high-income countries, although they still fell short of the WHO recommendations, with a median of only about half of infants still being breastfed (one quarter exclusively) at 6 months, and one third still breastfed at 12 months.

NNR2012 (11) included breastfeeding statistics for children born between 2004 and 2010 (depending on country). It identified that breastfeeding rates in the Nordic countries had increased a lot from the mid-1970s, but that both breastfeeding initiation and duration of exclusive breastfeeding had started to decrease in some of the countries. It was therefore stated as very important to further protect, promote, and support breastfeeding in all the Nordic countries. This seems to have had some positive effects (Table 3), but it is still imperative to improve the quality and regularity of breastfeeding statistics to plan appropriate actions and to follow up on their results.

Compared to the data in NNR2012 (11), both negative and positive changes can be seen in the most recent available data for children born in 2018 – 2022 (Table 3). Only Sweden and Iceland had data about breastfeeding during the first week of the infant’s life in both the time periods, and in both countries a decline could be seen from 97 to 93.7% and 98 to 83%, respectively. In Norway, the proportion of infants receiving any breastfeeding at 4 and 6 months declined somewhat among those born in 2018 compared with those born 2006 but remained the same at 9 and 12 months. However, the rate of exclusive breastfeeding at 5 months fell from 25 to 5%. Also in Sweden, a small declining trend could be seen for both exclusive and any breastfeeding at 4 months, while rates were relatively stable at 6 months, and the proportion still being breastfed at 12 months almost doubled from 16 to 28%. In Iceland, the proportion exclusively breastfed at 6 months had almost trebled from 8 to 22%, while any breastfeeding was relatively stable, slightly above 70%. Being breastfed at 12 months increased from 27 to 39%, and 24% were reported as still being breastfed at 18 months of age. Also in Finland, both the proportion exclusively breastfed and total duration increased substantially, with the proportion still breastfed at 9 months almost doubled from 39 to 75% and increased by 24 percentage points at 12 months: from 34 to 58%. In Denmark, breastfeeding rates during the first 6 months had increased.

The reasons for the changes in breastfeeding rates in the eight countries are not well studied. Possible reasons include changes in how long the mother and infant stay at the maternity ward and routines at the maternity wards, the information received during pregnancy, the duration of parental leave and its distribution between parents, the amount of support the parents receive both related to breastfeeding as such and child care more generally, and not least the competence about breastfeeding among staff within the health care system.

Formula feeding

If the mother does not want to breastfeed at all or if there is a problem with breastfeeding before the infant is 4 months of age (e.g. if breastmilk is not enough for the infant despite skilled breastfeeding counseling, more intensive breastfeeding, or if breastfeeding must be discontinued for medical or other reasons), the child should be fed infant formula. If possible, breastfeeding should be continued alongside formula feeding, as even small amounts of breastmilk have benefits for the infant. If the infant is 4 months or older, starting with solids together with continued breastfeeding and/or formula feeding could also be an option.

Manufacturers of infant formula strive to mimic the average nutrient composition of breastmilk and also add other constituents of breastmilk such as probiotics and prebiotics (62). The composition and ingredients of infant formula and follow-on formula are standardized through EU regulation. The EU regulation of infant formula (63) required in 2016 increased levels of vitamin D in infant formula compared with earlier regulation. This resulted in changed recommendations about vitamin D supplementation during the first year of life for infants fed formula in some Nordic countries (27–29). The changed EU regulation (63) also led to changed recommendations in Norway and Iceland regarding the common practice of using cod liver oil. However, in 2019, an amendment to the EU regulation lowered the upper level of vitamin D to the previous level due to concerns regarding too high intake of vitamin D among formula-fed infants.

The EU regulation from 2016 (63) also required increased levels of DHA. There is, however, no recommendation level for arachidonic acid (ARA) in infant formulas, even though the synthesis of both DHA and ARA from essential fatty acids is low in the first months of life, and international expert groups have brought up the importance to add both DHA and ARA to infant formulas (64–66).

Infant formula has previously been much higher in protein than breastmilk, but the levels have been decreasing and are now closer to that of breastmilk (67) (Table 2). This change will decrease the difference in protein intake between infants fed breastmilk and those fed infant formula and thus probably also health outcomes related to protein intake (see section Health effects of infant feeding; Overweight and obesity).

Unmodified milk from cows or other mammals (e.g. goats) is not suitable for children under 1 year of age (except in small amounts in food from the end of the first year). The reasons are that unmodified milk may overload the kidneys due to the high protein content and that the low iron content may contribute to iron deficiency. In infant formula, the quantity and quality of protein and fats have been modified to replicate breastmilk as much as possible, and it also contains more lactose, vitamins, and minerals than cow’s milk. Owing to these modifications, infant formula (and follow-on formula from 6 months) is suitable for infants, unlike regular cow’s milk.

Plant-based infant formulas are at present not available in stores in the Nordic countries although it may be purchased online. Plant-based milk alternatives such as soy, oat, and almond drinks and home-made milk alternative mixtures should not be given to infants during the first year, except in small amounts mixed with other foods (10). Drinks based on rice should not be given during the first 6 years due to its high content of arsenic.

Introduction of solid foods

Recommendations related to the introduction of solid foods

As described above, exclusive breastfeeding is recommended for about 6 months by most official bodies globally (22), including EFSA (9) and the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) (10). The recommendations regarding when solids should start vary, however, between at about 6 months (most common) and between 4 and 6 months (21).

Guidelines generally agree that solid food should not be introduced before the age of 4 months (21), and if extra food is needed before 4 months, infant formula should be given. EFSA states that some infants show developmental skills to handle semi-solids between 3 and 4 months of age and finger foods from around 4 months (but most not until 5–7 months) but adds that ‘the fact that complementary foods can be introduced before 6 months does not imply that this is necessary or desirable’ (9). Indeed, also in high-income countries, exclusive breastfeeding for 6 months provides protection from gastrointestinal infections compared with breastfeeding and introduction of solids from 4 months (68). So, if the infant is healthy and the mother wants to continue exclusive breastfeeding, she should not be encouraged or pressured to start giving solid foods before 6 months of age, when gradual transition into a diversified diet is recommended (see also section Timing below).

Regardless of age at introduction of solid foods, a varied diet based on all food groups including iron-rich foods is recommended (8, 26, 68) (see also section Plant-based diets). Early inclusion of potentially allergenic foods (e.g. peanuts, egg, fish, and cereals) is also recommended (9, 26, 68–70) (see also section Health effects of infant feeding; Atopy and Asthma).

Some foods can cause health risks if given during the first year (with increasing risk the younger the infant): foods naturally high in nitrate (e.g. leafy vegetables such as spinach, beet blast, arugula; water from some private wells) can cause methemoglobinemia (71), and honey may contain the bacteria Clostridium botulinum, which can cause botulism (72). In addition, when peanuts are given, it should not be as whole pieces as this might cause choking.

Priming for healthy and sustainable food habits

There is strong evidence for associations between maternal diet during pregnancy and lactation and children’s later food preferences, and if the mother has a healthy diet, there are good chances that the child will have it too (73, 74). However, when it comes to children’s later food habits, there are also many different potential mediators, moderators, confounders, and covariates related to both exposure and outcome that are not always included in studies (73). One very important factor to consider is the composition of the family diet in later childhood. Getting accustomed to new foods is not only about what the mother eats during pregnancy and lactation or even what the infant is given when starting complementary feeding. It is also very much about the family’s overall diet; if food is not served in the home, there is little chance for the child to secure it as a lasting accepted and preferred food. Here, the Nordic preschool system can play an important role as a large proportion of children from 1 to 6 years of age spend part of their day and eat some of their meals there.

Regardless of country, a relatively small proportion of populations eats according to recommendations. The intake of vegetables is usually much below recommendations in all age groups and genders, which is detrimental to public health. In addition, a major change in food habits, including a large increase in the amount of plant foods, has been suggested to both improve human health and to support environmental sustainability (75). Changing established food habits is difficult, and introducing healthy and sustainable food habits already in early childhood is therefore imperative. It has been suggested to start complementary feeding with the introduction of a variety of vegetables to increase the exposure to these foods (76). Unfortunately, many vegetables have bitter tastes and can therefore take a bit longer for the infant to accept (77).

At birth, infants have an inborn preference for the tastes sweet and umami and an inborn dislike for bitter and sour (77). A preference for sweetness matches well with the lactose-rich breastmilk, and sweet taste signals a higher energy content, which was advantageous in the beginning of evolution/humankind. However, it is less appropriate in the obesogenic society of today. Sugar should be avoided because it contains only calories and not the nutrients that infants need.

While a preference for salt is not inborn, it can develop early if salty foods are given (77, 78). Salt (sodium) should be avoided for infants due to their immature kidneys but also to avoid encouraging the development of a preference for salty taste. If children are given sugar and salt already from a young age, their preference for sugary and salty tastes will increase, and there is a strong evidence base associating a large intake of sugary and salty foods with clear negative health implications during the life course. Sugary drinks are, for instance, strongly associated with increased risk for overweight and obesity (79) and should not be given to children during the first 2 years (23). High salt intake has been shown to be associated with increased blood pressure already in infancy (80), and increased blood pressure is a major risk factor for stroke and cardiovascular disease in adulthood (81).

Bitter tastes are most likely disliked because it signals a risk of toxicity (77). When foods with bitter tastes, such as some vegetables, are first introduced, most infants react with reluctance to eat or even show distaste. There is a risk that parents take an initial dislike to heart and do not offer the unpopular food again. It is therefore crucial that parents are aware that these inborn preferences and dislikes exist and importantly can be modulated by early experiences, even as early as in utero (77). In their figure, Nekitsing and Hetherington (76) show how exposure to vegetables can work positively (green arrows) or negatively (red arrows) during four different (food) phases, from conception to the child eating family meals (Fig. 1). This could be an incentive for parents to improve their own diets, and many are also motivated to change when they expect a baby.

Fig. 1. From: Nekitsing and Hetherington (76) republished under a Creative Commons license.

In many Nordic countries, foods with a relatively neutral (e.g. potatoes) or sweet taste (e.g. carrots) have traditionally been used as the first foods when complementary feeding starts. Encouraging parents to introduce a variety of foods with ‘more demanding’ sensory qualities can be positive for later acceptance. A recent Swedish randomized controlled trial (RCT) (82) showed that starting complementary feeding with a systematic introduction of inherently sour or bitter-tasting Nordic fruits (apple), berries (raspberry, lingonberry, cranberry), roots (turnip, white radish), and vegetables (cauliflower) resulted in overall higher intakes of fruit and vegetables at 9, 12, and 18 months of age.

Although the child should be exposed to various vegetables and fruits in the 6–12 months period to increase acceptance and secure future food habits, fruits and vegetables have a low energy content and also often a low iron content. Infants and young children have small stomachs, and enough space should be ensured for energy and iron rich foods for the infant to meet energy and nutrient needs. This is especially important if a vegetarian or vegan diet is pursued (see also section Plant-based diets below).

Timing

Children’s food preferences start already in the womb with the amniotic fluid flavored by maternal diet, followed (for the breastfed infant) by a chemosensory continuity in the breastmilk (83). Breastfed infants therefore experience a large variation of flavors during feeding, partly due to the mother’s dietary habits and partly because the content of lactose and fat in the breastmilk changes during a breastfeed, which gives even larger variation for the infant. In contrast, formula-fed infants get the same flavor sensation every time, unless there is a change of brands.

It is sometimes stated that it is important to start introducing semi-solids no later than 4 months, sometimes even before 4 months, often referring to a study by Mennella et al. (84). This was an RCT testing if acceptance to bitter tastes, which usually are disliked, could be influenced by the age at introduction. They saw that switching infants fed on cow’s milk formulas to protein hydrolysate formula (PHF), which is very bitter, before 3.5 months was readily accepted, while a switch at 3.5 months was less accepted, although longer exposure increased acceptance. In an earlier study, they had seen that the introduction of PHF at 4 months or later was difficult (85), and they therefore concluded that their results suggest that the ‘window’ for early acceptance and long-term influences is beginning to close at about 3.5 months (84). These results cannot, however, be interpreted as evidence of a window of opportunity for the introduction of solids in breastfed infants.

It has been shown that breastfed infants faster get accustomed to and accept foods that the mother has eaten during pregnancy and lactation than noneaten foods and also faster than formula-fed infants, who only get the flavor experience of their mother’s diet from the amniotic fluid. For the individual family, the importance of accustoming infants to different tastes could be one aspect to consider when deciding at what time point they should introduce complementary foods to their infant. In Finland and Iceland, the introduction of (semi-) solid foods is recommended already at 4 months of age for formula-fed infants who do not get breastmilk at all, to ensure that the infant gets the sensory sensation of different tastes (86, 87). In Sweden, since 2011, parents are told that, regardless of feeding method, infants that seem interested in the family foods can be given ‘tiny tastes’ (≤1 mL) from 4 months (17 weeks) (72). The amounts of these tastes should not increase until about 6 months of age as the intention is sensory sensations, not increased nutrient intake, and is therefore seen as not competing with breastfeeding or formula feeding. However, a recent study showed that the earlier infants were given tiny tastes the earlier they ate larger amounts of solid foods and the shorter the breastfeeding duration (88).

There are several developmental milestones that signal that an infant is physically ready to start the process of changing from milk feeding to family foods (9). Some of these milestones are easy to detect, such as the ability to sit up without support and holding up the head (decreasing the risk for choking), the extrusion reflex of the tongue that prepared the infant for suckling decreases (making it easier for the infant to handle solids and not accidently spit it out), increased reaching and trying to pick up things, and an interest in putting those into the mouth. Some of these milestones can occur already at 3–4 months of age but more commonly at 5–7 months. A child showing these signs of physical maturation before 6 months of age does however not imply that there is a nutritional need for complementary feeding to start.

When discussing the timely introduction of complementary foods, the subject of sensitive and critical periods often comes up. It is important to differentiate between these. During a sensitive period, it is easier to learn a new behavior; after that, learning is still possible but can be more difficult (89). In contrast, critical periods are more of a window of opportunity, during which the exposure must take place for learning to occur (or be very much more difficult). Learning to eat lumpy foods (i.e. foods that need to be chewed) seems, for instance, to have a critical period around 6–9 months of age, and if these foods are introduced later, there is a greater risk for later feeding problems (90). When it comes to taste preferences among children, learning to like new tastes seems to be more about sensitive periods, that is, it is never too late to learn to accept new foods (89).

Mennella et al. (84) describe the sensitive periods as ‘age-related changes in functional plasticity for human flavour programming’, emphasizing that the early accustoming to the maternal diet through amniotic fluid and breastmilk works as a biological adaptation to the diet the infant will meet when complementary feeding starts. Phenotypic plasticity during development is also described by Burggren and Mueller (91). However, their description of sensitive/critical periods is more complex than the traditional definition, which has relatively distinct starting and stopping times. Burggren´s and Mueller’s definition includes a three-dimensional construct where time during development, dose (e.g. amount eaten), and the resulting phenotypic modification are all considered. Intuitively, this more multifaceted thinking goes well with the notion that although it is harder to learn new food habits when older, humans are able to learn new flavor preferences throughout their lifespan and when necessary, even change their whole diet.

Starting solids before 4 months is discouraged mainly because neither renal nor gastrointestinal function is mature enough before that age (9). The risk for choking is also greater. On the other hand, delaying the start of solids until after 6 months may increase the risk of iron deficiency. However, few infants in the western world are exclusively breastfed beyond 6 months, including the Nordic and Baltic countries (Table 3), so there is a scarcity of data to enable quantification of the risk. Indeed, EFSA (9) concludes that the biggest risk factors for iron deficiency are early umbilical cord clamping, being born preterm or with a low birth weight. It is, however, recommended that foods rich in iron should be among the first to be given to exclusively breastfed infants when the accustoming to solids starts.

How to introduce foods – parental-led or baby-led?

Children are evolutionary prepared to learn and adapt from cues in their environment. How fast an infant accepts new foods depends on several factors, for example, type of milk-feeding, level of neophobia, sensory sensitivity, and age at introduction, but the way new foods are introduced also affects the level of acceptance (92). Humans are social beings, and not only physiological but also psychological and social dimensions are important for how tastes, foods, and meals are experienced. There are a range of primary mechanisms that can be used to achieve increased acceptance for new foods (73), for example, associative conditioning (giving a new food together with something already familiar), repeated exposure (whereby the new food becomes more and more familiar), variety exposure (the larger the variety of foods the child has already accepted, the easier it is to introduce new similar foods), and social modeling (eating together with others, especially other children who already like the novel food, increases acceptance).

In most guideline documents on infant feeding, responsive feeding is recommended (21). This includes eating in a pleasant environment where the parent focuses on the infant through talk and eye-to-eye-contact. It is also commonly recommended to avoid using food as consolation or reward; hunger and satiety cues should guide the feeding. Parents should also avoid forcing children to eat and instead encourage self-feeding and self-regulation.

The term baby-led weaning has been used, and it usually includes that spoon-feeding by the parents is avoided and instead infants take the food themselves when solid food is introduced at around 6 months (93). However, the systematic review by D’Auria et al. found that there is no clear definition of the term, and most studies include varied combinations of spoon-feeding and self-feeding, making it difficult to evaluate the possible advantages and disadvantages of strictly avoiding spoon-feeding.

Plant-based diets

Regardless of what type of diet parents choose to give their children, it is important that they are knowledgeable so they can manage to plan and cook an adequate diet to support their child’s immediate and future health. Vegan and vegetarian diets may provide health benefits for both prevention and treatment of certain diseases, including cancer, cardiovascular disease, and diabetes among adults (10, 94). Due to the ongoing global transition to decreased meat intake and a more plant-based diet (75), there is an increased public health interest in the adequacy of vegetarian and vegan diets. Naturally nutrient-dense foods are in general preferable, but as certain nutrients are difficult or impossible to eat in sufficient amounts without intake of foods of animal origin, an increase in the availability of fortified foods and supplements has made it easier to plan and achieve an adequate vegan or vegetarian diet.

The view regarding whether a vegetarian or vegan diet can be given to children has changed radically during the last decades (95). A summary of existing guidelines from a range of health or government organizations from, for example, the USA, Europe, New Zealand, and Australia concludes that well-planned vegetarian and vegan diets, including relevant supplementation and fortified foods, are nutritionally adequate and appropriate for all stages of the life cycle, including pregnancy, lactation, infancy, and childhood (21). A large German study on dietary intake and health among vegetarian, vegan, and omnivore children aged 1–3 years concluded that energy intake was the same and normal growth achieved in all three groups (96). Regarding micronutrients and fatty acids, the results were more diverse, although showing that the vegan and vegetarian diets (including supplements and fortified foods) provided sufficient amounts of most micronutrients and had a better fat quality than the omnivore diet (97). The intake of some nutrients (vitamin E, vitamin B_1, folate, magnesium, iron) and fat quality were most favorable for the vegan children and least for the omnivores (vegetarians in-between), while the opposite was true for others (vitamin B₂, calcium, iodine, and DHA). The study identified some (potentially) critical nutrients: vitamin D, iodine, and DHA among children regardless of diet and in addition vitamin B₂, B₁₂, calcium, and iron for children on vegan or vegetarian diets.

The importance of careful planning and inclusion of supplementation and fortified foods is crucial when implementing a vegan or vegetarian diet to children as they need a more nutrient-dense diet than adults to ensure normal growth and development. The more restricted a diet is, that is, the fewer food types chosen, the more important the nutrient content of the foods eaten and the more knowledge required for planning the diet. When planning meals, it is also important to consider the combination of foods that may affect the uptake of different nutrients, for example, phytates decrease iron and zinc absorption, while vitamin C increases uptake. It is also necessary to know when supplements or enriched food products are needed to meet nutritional requirements as the consequences of low intake of some nutrients can be severe and irreversible. In fact, although ESPGHAN is among the organizations stating that a well-planned vegan diet is safe for children, they also state that ‘Vegan diets should only be used under appropriate medical or dietetic supervision’ (10).

A healthy and balanced vegetarian or vegan diet can be composed of legumes (beans, lentils, peas), whole-grain cereals, vegetables, fruit, berries, nuts, seeds, plant oils, plant-based drinks, and low-fat dairy products and eggs if included in the diet (94). Nutrients that require extra attention are vitamin B₁₂, vitamin D, iron, iodine, selenium, zinc, calcium, omega-3 (DHA), and protein. Good sources for some of these minerals, for example, selenium, may differ due to the amount in the soil where the plants were grown. For B₁₂ and several of the other mentioned nutrients, supplements or fortified foods are necessary to meet nutritional requirements. A de novo systematic review was performed within the NNR2023 project to assess whether the intake of vitamin B₁₂ from habitual diet or supplements is enough to cover the needs for groups most susceptible to vitamin B₁₂ deficiency; including pregnant and lactating women as well as infants, especially when a vegan or vegetarian diet is followed (98). Due to a lack of evidence, no conclusion could be made. While waiting for more research to be performed, pregnant and lactating women need to ensure an adequate intake of vitamin B₁₂ from supplements, foods enriched with sufficient amounts of vitamin B₁₂ or injections.

It is also necessary to ensure that children eating a plant-based diet can manage to eat enough food to sustain adequate growth and development. The composition of plant-based diets usually results in a high fiber and relatively low energy content. This can make it difficult for children to eat enough to meet their energy needs, especially for young children, as the volume of the food required can get too large. Parents therefore need to make sure that children follow their growth curves. The optimal level of dietary fiber in the diets of children is unknown, but EFSA suggests that from 1 year of age, a daily intake of 2 g of fiber/MJ is an adequate amount for achieving normal bowel movements and avoid constipation due to too low intake (99). The most recent dietary guidelines for Americans indicate a higher level, with a suggested 14 g of fiber/1000 kcal for children aged 12–23 months (approximately 3.3 g/MJ) (23). A de novo systematic review within the NNR2023 project found no clear associations between a high fiber intake and growth among children 0–5 years of age and found no studies on high fiber intake and its relation to iron status (16).

If the family eats a vegetarian or vegan diet, continued breastfeeding after 1 year of age or longer is recommended (94). For vegan families where the infant requires more milk than breastmilk, the options are limited. At present, there are no vegan infant formulas for sale in stores in the Nordic countries although it may be purchased online.

A growing assortment of various plant-based products and processed foods in recent years has made it easier to achieve a healthy plant-based diet also for young children, and many of these foods are fortified with micronutrients that would otherwise be nonexistent, with low concentration or low bioavailability. It is important to be aware that the levels of fortification of similar foods can vary manifold (100). Parents therefore need to read the information on packages carefully, so their children do not exceed tolerable upper limits of nutrients (e.g. iodine) through eating a combination of fortified foods with high levels of fortification, especially if they also eat supplements.

Regulations regarding the fortification of different foods vary within Europe (101). For instance, in Sweden, it is since 2018 legally required for producers to add vitamin D in most milk-based products and their nonmilk counterparts (based on soy, oat, rice, and almond), including organic products (102). In many, but not all, plant-based alternatives for milk and yogurts sold in Sweden, other vitamins and minerals are also added, for example, vitamin B₁₂, iron, calcium, etc., but in organic products only legally required fortification is allowed (i.e. vitamin D). It is also important to realize that processed foods are not necessarily healthy just because they are plant based. Note that rice drinks (and rice cakes) should not be given to children below 6 years of age due to the content of arsenic (10).

Adequate intakes of vitamin B₁₂ by pregnant and lactating women are crucial to avoid irreversible, negative effects on the fetus and infant (10). The main natural sources of vitamin B₁₂ are foods of animal origin. Small amounts of B₁₂ analogues can be found in seaweed and fermented vegetables, but these are not bioavailable for humans and are therefore not a source of B₁₂ (94, 103). In addition, seaweed (and kelp) should be used with great caution by pregnant and breastfeeding women and infants due to the high variability in iodine content.

Health effects of infant feeding

Many nutrients and biologically active substances are found in breastmilk, including vitamins, minerals, fatty acids, and immune factors, and many of these have proven positive effects on health. Nutrients in human milk have multiple functions related to optimal growth, development, and physiological functions. Deficiencies during the first 2 years may cause permanent damage. Numerous studies have indicated long-term beneficial effects of breastfeeding on health for both the infant (Table 4) and the breastfeeding mother (3). Indeed, Victora et al. even characterize breastmilk as a personalized medicine for infants.

Table 4. Evidence for health effects associated with infant feeding.

Outcome	Evidence	References
Infections	Convincing evidence that breastfeeding has a protective effect against overall infections, acute otitis media, gastrointestinal infections, and respiratory tract infections in childhood.	(3, 68, 104, 105)
Overweight and obesity	Probable evidence that longer duration of breastfeeding, exclusive or any, have a protective effect against overweight and obesity in childhood and adolescence, as well as in the general population. Probable evidence that high protein intake in during the first 18 months cause higher BMI later in childhood.	(3, 15, 93, 94, 95, 96, 97, 98, 99, 100, 101) (3, 14, 106–114)
Celiac disease	Moderate to high level of confidence that breastfeeding during or after introduction of gluten has no protective effect against celiac disease in early childhood. The amount of gluten at introduction may have an effect on the risk for celiac disease, but whether it prevents celiac disease or merely delay the start is unclear. The evidence is insufficient to conclude which age is best for the introduction of gluten; therefore the recommendation is to start giving gluten containing foods when complementary feeding is started.	(9, 10, 101) (9, 10, 112)
Type 1 and 2 diabetes mellitus (T1DM and T2DM)	Limited to moderate evidence that any breastfeeding and longer duration of any or exclusive breastfeeding protects against T1DM. Moderate to strong evidence that introduction of gluten, cow’s milk, and fruit increase the risk for T1DM Probable evidence that any breastfeeding has a protective effect against T2DM. The evidence for a stronger protective effect for longer duration of breastfeeding is limited but suggestive.	(3, 10, 102, 103) (3, 10, 115, 116)
Cardiovascular disease	Probable evidence that breastfeeding has a small reductive effect on blood pressure and lower triglycerides in childhood and adolescence, as well as a small reduction in blood cholesterol levels in adulthood for the breastfed infant.	(12, 104, 105, 106, 107, 108, 109, 110, 111) (12, 115, 117–123)
Brain development	Prolonged breastfeeding has been related to improved performance in intelligence tests and a positive effect of breastfeeding on cognition and visual acuity	(3, 108, 109, 112, 113, 114, 115, 116) (3, 106, 120, 122, 124–128)
Atopy and asthma	The evidence is strong that the previous recommendation to avoid allergenic foods during at least the first 12 months increase the risk for atopy and asthma. There is moderate evidence that introduction of well-cooked egg, and peanuts in populations with a high degree of peanut allergy, as part of complementary feeding but not before 4 months of age, may decrease the risk of atopy and asthma. There is low evidence that avoiding supplementation with regular cow’s milk formula during the first week of life in breastfed infants decrease the risk for atopy and asthma. No conclusions can be drawn for preventive effects of breastfeeding in itself on the risk for atopic diseases or asthma in children.	(12, 57, 58, 113, 117, 118, 119, 120) (12, 69, 70, 124, 129–132)

The positive effects seen for breastfeeding depend to a considerable degree on the breastmilk itself and its unique composition (133). The effects may also depend on the physical closeness during the act of breastfeeding or on other associated factors. An important factor is also what nonbreastfed or partly breastfed infants are fed instead of breastmilk.

Interpreting the results of different studies is difficult because the definition of breastfeeding varies between studies and the methodology used to assess breastfeeding is often unclear. The impact of breastfeeding and the level of evidence often varies for different health-related outcomes. Research in this area has been active not least because of the high interest in the programming effect that diet can have on future health (133).

Infections

There is convincing evidence that breastfeeding has a protective effect against overall infections, acute otitis media, gastrointestinal infections, and respiratory tract infections also in high-income countries (3). Breastmilk contains many protective factors that might exert long-term health benefits, and the immunological protection against otitis media appears to last for some years after cessation of breastfeeding (105). The magnitude of the effect varies depending on the specific outcome and the exclusiveness of breastfeeding. Systematic reviews cited in Victora et al. (3) showed that longer and/or more breastfeeding (e.g. ever vs. never, exclusive vs. not exclusive, long duration vs. shorter) resulted in approximately 30% risk reduction for otitis media and lower respiratory tract infections during the first 2 years, and for gastroenteritis during the first 5 years. Earlier, it has also been stated that exclusive (or predominant) breastfeeding for 6 months compared to 3–4 months gives better protection against mild gastrointestinal infections (68) and that any breastfeeding reduces the risk of diarrhea (104).

Overweight and obesity

Longer duration of breastfeeding, exclusive or any, has a probable protective effect against overweight and obesity in childhood and adolescence as well as reduces the occurrence of overweight and obesity in the general population by about 30% (3, 106–108). Mechanisms linking breastfeeding to lower incidence of early childhood obesity are still mostly unclear, but several plausible pathways have been suggested, for example, the changing nutrient composition of breastmilk during a breastfeed improves recognition of satiety cues improving self-regulation of intake (109), the lower protein content of breastmilk compared with infant formula (14), protective effects by non-nutrient bioactive components in breastmilk (110, 111), and epigenetic effects and programming connected with breastmilk (113).

There is probable evidence for a cause-and-effect association between higher total protein intake during the first 18 months of age and higher BMI later in childhood as shown by a de novo systematic review within the NNR2023 project by Arnesen et al. (14). The meta-analysis of five cohort studies showed that for each additional E% of protein, BMI (kg/m²) increased with 0.06 (95% confidence interval [CI]: 0.03–0.1) BMI units. This seemed to be driven by the proportion of protein of animal origin, as no associations were found between intake of plant-based proteins and later BMI or body fat (albeit based on few studies). Despite the decreasing levels of protein in infant formula to better match the content in breastmilk, it will take time before this may be reflected in the prevalence of overweight and obesity in the population.

The WHO growth charts from 2006 (114) are based on breastfed infants and give a good picture of normal growth. Use of the WHO growth charts for children is therefore recommended (112). Using growth charts based on children born when the breastfeeding rates were lower than nowadays (like in the 1970s) may lead to misinterpretations by health care staff, as infant formulas at that point in time contained more protein than modern formulas. This could cause erroneous advice about the need for additional food to breastfed infants, inadvertently increasing the risk for shortened breastfeeding duration and associated long-term health effects.

Celiac disease

Previously, it was thought that breastfeeding could protect from celiac disease, especially if the infant was still breastfed when gluten was introduced. However, a later meta-analysis including two large RCTs has not confirmed this but instead suggested that the later introduction of gluten led to a delay of the start of celiac disease rather than prevented it (134). Therefore, both EFSA (9) and ESPGHAN (10) recommend introducing gluten-containing foods during the first 12 months when other complementary foods are introduced. However, they recommended that the amount of gluten should be kept low during introduction and large quantities avoided onwards throughout infancy.

Diabetes mellitus, type 1 and 2

Whether different aspects of infant feeding including breastfeeding and gluten intake could be involved in the development of type 1 diabetes mellitus (T1DM) has been studied for many years. ESPGHAN concluded in 2017 that breastfeeding at the time of introduction of gluten did not influence the risk of T1DM (10). Very early introduction of gluten (before 3 months) was associated with a higher risk to develop diabetes among children with increased risk. However, starting with gluten after 3 months of age did not increase the risk, so the recommendation to introduce gluten when other foods are introduced sometime between 4 and 12 months of age was not changed. Later evidence suggests, however, limited to moderate evidence for an increased risk of T1DM for less or no breastfeeding (135) and moderate to high certainty for an increased risk with shorter breastfeeding (exclusive or any) and earlier introduction to gluten, cow’s milk, or fruit (116). There is probable evidence that any breastfeeding has a protective effect on type 2 diabetes mellitus (T2DM) (3), which might be connected to the association with the risk for overweight and obesity.

Cardiovascular disease

The influence of breastfeeding on the risk of cardiovascular disease is unclear, but there is probable evidence of small but significant effects on the reduction of blood pressure levels and serum cholesterol levels in adulthood for the breastfed child (12). The association with blood pressure levels in childhood is, however, not clear as there are studies not showing this association (115). One possible influencing factor could be that a higher intake of n-3 fatty acids by breastmilk might affect the elasticity of the blood vessels. A protective effect against high blood pressure has been seen for the breastfeeding mother (136). The lower cholesterol level in adulthood found among those who were breastfed in infancy might be the result of the metabolic effects of constituents in breastmilk such as cholesterol and n-3 fatty acids (118). Breastfeeding has been reported to have a protective effect on triglyceride levels in childhood and adolescence (123). Indeed, the increased risk of overweight and obesity in later life for nonbreastfed infants compared with breastfed infants is in itself a risk factor for cardiovascular diseases (121).

Brain development

Breastfeeding has been related to improved performance in intelligence tests, and a positive effect of breastfeeding on cognition was observed in a systematic review (3, 125). The favorable effect of breastfeeding on the healthy neurological development of the infant might be caused by the high content of DHA in breastmilk because this fatty acid is present in high amounts in nerve cell membranes.

However, the interpretation of studies on the association between breastfeeding and neurological development is complicated because the outcome is not only influenced by whether the child is breastfed or not, nor only by what children are fed instead of breastmilk and the exposure that this gives. The interaction between the mother/caregiver and the infant in the feeding situation is also important. It has also been shown that genes might affect the associations between breastfeeding and outcomes such as cognition (124), and this suggests that genetic aspects should be included in future studies.

Positive results from the PROBIT study in Belarus that compared control areas to intervention areas in which breastfeeding was promoted also provide quite strong support for positive associations between breastfeeding and neurological development (126). The nonresults in another paper from the same group (127) can probably be explained by the fact that this latter paper compared children who were exclusively breastfed for 3 or 6 months from both the intervention and control areas.

Other studies have also shown beneficial associations for breastfeeding with cognitive measures in children (120, 122). Oddy and coworkers concluded that although the effect sizes were small, any breastfeeding for 4 months or longer was associated with improved neurological outcomes in children aged 1 to 3 years after adjustment for multiple confounders (120). In a Danish national birth cohort, breastfeeding duration of 1 month or shorter compared with longer periods was associated with lower IQ even after adjustment for maternal IQ and other factors (122). However, the authors stated that there might be other pre- and postnatal factors that influence child IQ not taken into account. One prenatal factor that may influence cognitive development in children is supplementation with omega-3 fatty acids during pregnancy although a recent systematic review concluded that the evidence was limited (128).

Atopy and asthma

The recommendations related to infant feeding and development of atopic diseases and asthma have changed over time. Previous advice on allergy prevention included exclusive breastfeeding for 6 months and avoidance of allergens through the delayed introduction of potentially allergenic foods to the infant’s diet until after 12 months or longer and sometimes also avoidance for the woman during pregnancy and lactation. Immunomodulatory qualities of breastmilk were thought to prevent conditions such as asthma, especially if a family history of atopy was present. The systematic literature review performed for NNR2012 (12) found the existing scientific evidence on the associations between avoidance of allergenic foods during pregnancy and lactation, duration of exclusive breastfeeding, and age at introduction of complementary feeding on later development of atopic diseases and asthma limited and contradictive, and therefore no specific recommendations regarding introduction of allergenic foods were given.

Since then, results from a number of new RCTs (e.g. 129–132) and systematic reviews (e.g. (117, 119) have been published. The evidence has been strongest for decreasing prevalence for allergies against peanuts and egg with early introduction. This has resulted in updated guidelines from the European Academy of Allergy and Clinical Immunology (EAACI) (70), focusing on preventing food allergy during the first 5 years. The EAACI-guidelines recommend that when solid foods are introduced, well-cooked eggs should be among the foods given, and in populations with high prevalence of peanut allergy, peanuts (in an age-appropriate form) should also be among the served food. It is also advised against giving cow’s milk infant formula during the first week of life to breastfed infants, but the level of evidence is low. Joint guidelines from USA and Canada not only have similar messages but also include a suitable age stating that to prevent peanut and egg allergy, these foods should be introduced around 6 months but not before 4 months (69).

After the publication of these guidelines (69, 70), two new RCTs have been published suggesting that the introduction of peanuts already at 3 months is even more efficient in decreasing the prevalence of allergy, without negative effects on breastfeeding (130, 132). The recommendation of exclusive breastfeeding for the first 6 months is therefore put into question. However, as the research teams encouraged their participants to breastfeed, it is not sure that breastfeeding would remain unaffected in the general public if a very early introduction of solids is recommended to decrease the risk for allergies. Indeed, a Swedish study saw that a change in the infant feeding recommendations in 2011, suggesting the introduction of tiny tastes (<1 mL) to interested infants already from 4 months, but without increasing the amounts until about 6 months of age, inadvertently led to shorter breastfeeding duration (88). It seems prudent to suggest that the introduction of allergenic foods should start when complementary feeding is started but not before 4 months.

Genes might have modifying effects also on the associations between breastfeeding and outcomes such as allergies (124), and this suggests that genetic aspects should be included in future studies. Very little is known about the possibilities of active prevention of allergies and asthma by adding specific food components or dietary supplements such as n-3 fatty acids, pre- and probiotics, or vitamins to the diets of pregnant or lactating women or to the diets of infants. Any positive effect of such additions remains to be shown.

References

1.	Fleming TP, Watkins AJ, Velazquez MA, Mathers JC, Prentice AM, Stephenson J, et al. Origins of lifetime health around the time of conception: causes and consequences. Lancet 2018; 391(10132): 1842–52. doi: 10.1016/S0140-6736(18)30312-X
2.	Stephenson J, Heslehurst N, Hall J, Schoenaker D, Hutchinson J, Cade JE, et al. Before the beginning: nutrition and lifestyle in the preconception period and its importance for future health. Lancet 2018; 391(10132): 1830–41. doi: 10.1016/S0140-6736(18)30311-8
3.	Victora CG, Bahl R, Barros AJ, Franca GV, Horton S, Krasevec J, et al. Breastfeeding in the 21st century: epidemiology, mechanisms, and lifelong effect. Lancet 2016; 387(10017): 475–90. doi: 10.1016/S0140-6736(15)01024-7
4.	Daníelsdóttir S, Ingudóttir J, editors. The first 1000 days in the Nordic countries: policy recommendations. Copenhagen: Nordic Council of Ministers; 2022.
5.	Darling JC, Bamidis PD, Burberry J, Rudolf MCJ. The first thousand days: early, integrated and evidence-based approaches to improving child health: coming to a population near you? Archiv Dis Childhood 2020; 105(9): 837–41. doi: 10.1136/archdischild-2019-316929
6.	Stoody EE, Spahn JM, Casavale KO. The pregnancy and birth to 24 months project: a series of systematic reviews on diet and health. Am J Clin Nutr 2019; 109(Suppl_7): 685S–97S. doi: 10.1093/ajcn/nqy372
7.	World Health Assembly. Infant and young child feeding. WHO Resolution World Health Assembly (WHA71.9). Agenda item 12.6 Infant and young child feeding. 2018.
8.	WHO & UNICEF. Indicators for assessing infant and young child feeding practices. Definitions and measurement methods. Geneva: World Health Organization and the United Nations Children’s Fund (UNICEF); 2021.
9.	EFSA-NDA Panel (EFSA Panel on Nutrition, Novel Foods and Food Allergens). Scientific opinion: appropriate age range for introduction of complementary feeding into an infant’s diet. EFSA Journal 2019; 17(9): 5780. doi: 10.2903/j.efsa.2019.5780
10.	Fewtrell M, Bronsky J, Campoy C, Domellof M, Embleton N, Fidler Mis N, et al. Complementary feeding: a position paper by the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) Committee on Nutrition. J Pediatr Gastroenterol Nutr 2017; 64(1): 119–32. doi: 10.1097/MPG.0000000000001454
11.	Nordic Council of Ministers. Nordic nutrition recommendations 2012. Integrating nutrition and physical activity. 5th ed. 2014, 627 p. Nordisk Ministerråd, Copenhagen. doi: 10.6027/Nord2014-002
12.	Hörnell A, Lagström H, Lande B, Thorsdottir I. Breastfeeding, introduction of other foods and effects on health: a systematic literature review for the 5th Nordic Nutrition Recommendations. Food Nutr Res 2013; 57: 20823. doi: 10.3402/fnr.v57i0.20823
13.	Hörnell A, Lagström H, Lande B, Thorsdottir I. Protein intake from 0 to 18 years of age and its relation to health: a systematic literature review for the 5th Nordic Nutrition Recommendations. Food Nutr Res 2013; 57: 21083. doi: 10.3402/fnr.v57i0.21083
14.	Arnesen EK, Thorisdottir B, Lamberg-Allardt C, Bärebring L, Nwaru B, Dierkes J, et al. Protein intake in children and growth and risk of overweight or obesity: a systematic review and meta-analysis. Food Nutr Res 2022; 66: 8242. doi: 10.29219/fnr.v66.8242
15.	Bärebring L, Nwaru BI, Lamberg-Allardt C, Thorisdottir B, Ramel A, Söderlund F, et al. Supplementation with long chain n-3 fatty acids during pregnancy, lactation, or infancy in relation to risk of asthma and atopic disease during childhood: a systematic review and meta-analysis of randomized controlled clinical trials. Food Nutr Res 2022; 66: 8842. doi: 10.29219/fnr.v66.8842
16.	Dierkes J, Nwaru BI, Ramel A, Arnesen EK, Thorisdottir B, Lamberg-Allardt C, et al. Dietary fiber and growth, iron status and bowel function in children 0–5 years old: a systematic review. Food Nutr Res 2023; 67: 9011. doi: 10.29219/fnr.v67.9011
17.	Blomhoff R, Andersen R, Arnesen EK, Christensen JJ, Eneroth H, Erkkola M, et al. Nordic nutrition recommendations 2023. Copenhagen: Nordic Council of Ministers,; 2023. p. 388.
18.	Christensen JJ, Arnesen EK, Andersen R, Eneroth H, Erkkola M, Hoyer A, et al. The Nordic nutrition recommendations 2022-principles and methodologies. Food Nutr Res 2020; 64: 4402. doi: 10.29219/fnr.v64.4402
19.	Rollins NC, Bhandari N, Hajeebhoy N, Horton S, Lutter CK, Martines JC, et al. Why invest, and what it will take to improve breastfeeding practices? Lancet 2016; 387(10017): 491–504. doi: 10.1016/S0140-6736(15)01044-2
20.	World Health Assembly. Global strategy for infant and young child feeding. The optimal duration of exclusive breastfeeding. World Health Assembly (WHA54). Provisional agenda item 13.1. Global strategy for infant and young child feeding. The optimal duration of exclusive breastfeeding; 2001.
21.	National Academies of Sciences Engineering and Medicine. Feeding infants and children from birth to 24 months: summarizing existing guidance. Washington, DC: The National Academies Press; 2020.
22.	Scientific Advisory Committee on Nutrition (SACN). Feeding in the first year of life 2018. Available from: https://www.gov.uk/government/publications/feeding-in-the-first-year-of-life-sacn-report [cited 22 January 2024].
23.	U.S. Department of Agriculture (USDA) and U.S. Department of Health and Human Services (HHS). Dietary Guidelines for Americans, 2020-2025. 9 ed. December 2020. Available at https://www.dietaryguidelines.gov/
24.	Public Health Agency of Canada (PHAC). Chapter 6: breastfeeding. 2017. In: Family-centred maternity and newborn care: National Guidelines [Internet]. Available from: https://www.canada.ca/en/public-health/services/maternity-newborn-care-guidelines.html [cited 10 August 2022].
25.	National Health and Medical Research Council. Infant feeding guidelines: summary. Canberra: National Health and Medical Research Council. 2012. Available from: www.nhmrc.gov.au/guidelines-publications/n56b.
26.	WHO. WHO guideline for complementary feeding of infants and young children 6–23 months of age. Geneva: World Health Organization; 2023.
27.	Embætti landlæknis [Directorate of Health, Iceland]. Næring ungbarna. [Infant nutrition]. Leiðbeiningar um ung- og smábarnavernd [Guidelines for the protection of young children and infants]. Directorate of Health Reykjavik, Iceland; 2021.
28.	Helsedirektoratet [Norwegian Directorate of Health]. Nye råd om D-vitamintilskudd og tran til spedbarn [New advice on vitamin D supplements and cod liver oil for infants]. 2020. Available from: helsedirektoratet.no/nyheter/nye-rad-om-d-vitamintilskudd-og-tran-til-spedbarn [cited 10 December 2022].
29.	VRN (Valtion Ravitsemus-Neuvottelukunta) [National Nutrition Council of Finland]. Recommended intake of vitamin D supplements for infants. 2018. Finnish Food Authority, Seinäjoki. https://www.ruokavirasto.fi
30.	Andreas NJ, Kampmann B, Mehring Le-Doare K. Human breast milk: a review on its composition and bioactivity. Early Hum Dev 2015; 91(11): 629–35. doi: 10.1016/j.earlhumdev.2015.08.013
31.	Fischer Fumeaux CJ, Garcia-Rodenas CL, De Castro CA, Courtet-Compondu MC, Thakkar SK, Beauport L, et al. Longitudinal analysis of macronutrient composition in preterm and term human milk: a prospective cohort study. Nutrients 2019; 11: 1525. doi: 10.3390/nu11071525
32.	Kim SY, Yi DY. Components of human breast milk: from macronutrient to microbiome and microRNA. Clin Exp Pediatr 2020; 63(8): 301–9. doi: 10.3345/cep.2020.00059
33.	Sanchez C, Fente C, Regal P, Lamas A, Lorenzo MP. Human milk oligosaccharides (HMOS) and infant microbiota: a scoping review. Foods 2021; 10: 1429. doi: 10.3390/foods10061429
34.	Perrella S, Gridneva Z, Lai CT, Stinson L, George A, Bilston-John S, et al. Human milk composition promotes optimal infant growth, development and health. Semin Perinatol 2021; 45(2): 151380. doi: 10.1016/j.semperi.2020.151380
35.	Bravi F, Wiens F, Decarli A, Dal Pont A, Agostoni C, Ferraroni M. Impact of maternal nutrition on breast-milk composition: a systematic review. Am J Clin Nutr 2016; 104(3): 646–62. doi: 10.3945/ajcn.115.120881
36.	Keikha M, Bahreynian M, Saleki M, Kelishadi R. Macro- and micronutrients of human milk composition: are they related to maternal diet? A comprehensive systematic review. Breastfeed Med 2017; 12(9): 517–27. doi: 10.1089/bfm.2017.0048
37.	Eisha S, Joarder I, Wijenayake S, McGowan PO. Non-nutritive bioactive components in maternal milk and offspring development: a scoping review. J Dev Orig Health Dis 2022; 13(6): 665–73. doi: 10.1017/S2040174422000149
38.	Olafsdottir AS, Wagner KH, Thorsdottir I, Elmadfa I. Fat-soluble vitamins in the maternal diet, influence of cod liver oil supplementation and impact of the maternal diet on human milk composition. Ann Nutr Metab 2001; 45(6): 265–72. doi: 10.1159/000046737
39.	Braegger C, Campoy C, Colomb V, Decsi T, Domellof M, Fewtrell M, et al. Vitamin D in the healthy European paediatric population. J Pediatr Gastroenterol Nutr 2013; 56(6): 692–701. doi: 10.1097/MPG.0b013e31828f3c05
40.	Brustad M MH. Vitamin D – a scoping review for Nordic Nutrition Recommendations 2023. Food Nutr Res 2023; 67: 10230. doi: 10.29219/fnr.v67.10230
41.	Hojsak I, Bronsky J, Campoy C, Domellof M, Embleton N, Mis NF, et al. Young child formula: a position paper by the ESPGHAN Committee on Nutrition. J Pediatr Gastroenterol Nutr 2018; 66(1): 177–85. doi: 10.1097/MPG.0000000000001821
42.	Domellof M. Iron requirements in infancy. Ann Nutr Metab 2011; 59(1): 59–63. doi: 10.1159/000332138
43.	EFSA NDA Panel (EFSA Panel on Nutrition, Novel Foods and Food Allergens). Scientific opinion on dietary reference values for fats, including saturated fatty acids, polyunsaturated fatty acids, monounsaturated fatty acids, trans fatty acids, and cholesterol. EFSA J 2010; 8(3): 5. doi: 10.2903/j.efsa.2010.1461
44.	Biddulph C, Holmes M, Kuballa A, Davies PSW, Koorts P, Carter RJ, et al. Human milk oligosaccharide profiles and associations with maternal nutritional factors: a scoping review. Nutrients 2021; 13(3): 965. doi: 10.3390/nu13030965
45.	Han SM, Derraik JGB, Binia A, Sprenger N, Vickers MH, Cutfield WS. Maternal and infant factors influencing human milk oligosaccharide composition: beyond maternal genetics. J Nutr 2021; 151(6): 1383–93. doi: 10.1093/jn/nxab028
46.	Bode L. Human milk oligosaccharides: every baby needs a sugar mama. Glycobiology 2012; 22(9): 1147–62. doi: 10.1093/glycob/cws074
47.	Doherty AM, Lodge CJ, Dharmage SC, Dai X, Bode L, Lowe AJ. Human milk oligosaccharides and associations with immune-mediated disease and infection in childhood: a systematic review. Front Pediatr 2018; 6: 91.
48.	Triantis V, Bode L, van Neerven RJJ. Immunological effects of human milk oligosaccharides. Front Pediatr 2018; 6: 190. doi: 10.3389/fped.2018.00190.
49.	Theurich MA, Davanzo R, Busck-Rasmussen M, Diaz-Gomez NM, Brennan C, Kylberg E, et al. Breastfeeding rates and programs in Europe: a survey of 11 national breastfeeding committees and representatives. J Pediatr Gastroenterol Nutr 2019; 68(3): 400–7. doi: 10.1097/MPG.0000000000002234
50.	Vaz JS, Maia MFS, Neves PAR, Santos TM, Vidaletti LP, Victora C. Monitoring breastfeeding indicators in high-income countries: levels, trends and challenges. Matern Child Nutr 2021; 17(3): 13137. doi: 10.1111/mcn.13137
51.	Amning og udsættelse for tobaksrøg i første leveår [breastfeeding and exposure to tobacco smoke in the first year of life] [Internet]. Sundhedsdatastyrelsen. Available from: https://www.esundhed.dk/Registre/Den-nationale-boernedatabase/Amning-og-udsaettelse-for-tobaksroeg-i-foerste-leveaar [cited 22 January 2024].
52.	Ikonen Riikka, Hakulinen Tuovi, Lyytikäinen Arja, Mikkola Kaija, Niinistö Sari, Sarlio Sirpa, et al. Imeväisikäisten ruokinta suomessa vuonna 2019 [Infant feeding in Finland 2019]. Helsinki, Finland: National Institute for Health and Welfare (THL); 2020.
53.	Magnúsdóttir O, Guðmundsdóttir S. Brjóstagjöf og næring barna á íslandi 2018–2021 [Report on breastfeeding and nutrition in infancy and young child health care in Iceland 2018–2021]. Reykjavik: Þróunarmiðstöð íslenskrar heilsugæslu [Development Centre for Primary Healthcare in Iceland (DCPHI)]; 2022.
54.	Myhre J, Andersen L, Kristiansen A. Spedkost 3. Landsomfattende undersøkelse av kostholdet blant spedbarn i Norge, 6 måneder [spedkost 3. Nationwide survey of the diet among infants in Norway, 6 months]. Oslo: Folkehelseinstituttet og Universitetet i Oslo; 2020.
55.	Paulsen MM, Myhre JB, Andersen LF, Kristiansen AL. Spedkost 3. Landsomfattende undersøkelse av kostholdet blant spedbarn i norge, 12 måneder [spedkost 3. Nationwide dietary survey among infants in Norway, age 12 months]. Rapport 2020. Oslo: Folkehelseinstituttet og Universitetet i Oslo; 2020.
56.	Socialstyrelsen [National Board of Health and Welfare]. Statistikdatabas för amning [Statistical database for breastfeeding]. Available from: https://sdb.socialstyrelsen.se/if_amn/
57.	Socialstyrelsen. Statistik om amning 2021 [Statistics on breastfeeding children born 2021]. 2023-09-26. Report No.: 2023-9-8757. Statistics Sweden [Statistikmyndigheten; SCB]. Solna
58.	Official Statistics in Estonia. Health statistics and research database. Tallinn, Estonia. Available from: https://statistika.tai.ee/pxweb/en/Andmebaas/Andmebaas__01Rahvastik__02Synnid/SR90.px/ [cited 22 January 2024].
59.	Veselibas statistikas datubāse [Latvia Health Statistics Database] [Internet]. Available from: https://statistika.spkc.gov.lv/pxweb/lv/Health/Health__Mates_berna_veseliba/MCH100_kruts_barosana.px/ [cited 22 January 2024].
60.	Basys V, Drazdienė N, Ramašauskaitė D, Vezbergienė N, Isakova J. Gimimų medicininiai duomenys 2020 [Medical data of births, 2020]. In: Institute of Hygiene, editor. Vilnius, Lithuania; 2021. Available from: https://www.hi.lt/uploads/pdf/leidiniai/Statistikos/Gimimu/gimimai_2020.pdf [cited 22 November 2023].
61.	Žilvinė Našlėnė, Indrė Petrauskaitė, Aušra Želvienė. Higienos instituto sveikatos informacijos centras. Lietuvos vaikų sveikatos būklės pokyčiai ir netolygumai, 2020 [Institute of Hygiene Health Information Center. Changes and inequalities in the health status of Lithuanian children]. In: Higienos institutas, editor. Vilnius 2020. Available from: www.hi.lt [cited 23 November 2022].
62.	Salminen S, Stahl B, Vinderola G, Szajewska H. Infant formula supplemented with biotics: current knowledge and future perspectives. Nutrients 2020; 12(7): 1952. doi: 10.3390/nu12071952
63.	EUR-Lex 2016/127. Infant and follow-on formula - composition and information. 2015. https://eur-lex.europa.eu/eli/reg_del/2016/127/oj
64.	Lien EL, Richard C, Hoffman DR. Dha and ara addition to infant formula: current status and future research directions. Prostaglandins Leukot Essent Fatty Acids 2018; 128: 26–40. doi: 10.1016/j.plefa.2017.09.005
65.	Koletzko B, Bergmann K, Brenna JT, Calder PC, Campoy C, Clandinin MT, et al. Should formula for infants provide arachidonic acid along with DHA? A position paper of the European Academy of Paediatrics and the Child Health Foundation. Am J Clin Nutr 2020; 111(1): 10–16. doi: 10.1093/ajcn/nqz252
66.	Hopperton KE, Pitino MA, Walton K, Kiss A, Unger SL, O’Connor DL, et al. Docosahexaenoic Acid and Arachidonic Acid levels are correlated in human milk: implications for new European infant formula regulations. Lipids 2022; 57(3): 197–202. doi: 10.1002/lipd.12338
67.	Commission Directive 2013/46/EU of 28 August 2013 amending Directive 2006/141/EC with regard to protein requirements for infant formulae and follow-on formulae. 2013. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32013L0046
68.	Kramer MS, Kakuma R. Optimal duration of exclusive breastfeeding. Cochrane Database Syst Rev 2012; 8: CD003517. doi: 10.1002/14651858.CD003517.pub2
69.	Fleischer DM, Chan ES, Venter C, Spergel JM, Abrams EM, Stukus D, et al. A consensus approach to the primary prevention of food allergy through nutrition: guidance from the American Academy of Allergy, Asthma, and Immunology; American College of Allergy, Asthma, and Ammunology; and the Canadian Society for Allergy and Clinical Immunology. J Allergy Clin Immunol Pract 2021; 9(1): 22–43.e4. doi: 10.1016/j.jaip.2020.11.002
70.	Halken S, Muraro A, de Silva D, Khaleva E, Angier E, Arasi S, et al. EAACI guideline: preventing the development of food allergy in infants and young children (2020 update). Pediatr Allergy Immunol 2021; 32(5): 843–58. doi: 10.1111/pai.13496
71.	Livsmedelsverket [Swedish National Food Agency]. Nitrat och nitrit i livsmedel. Riskhanteringsrapport [Nitrate and nitrite in food. Risk management report]. 2017. Contract No.: 18: 1. Livsmedelsverket, Uppsala.
72.	Livsmedelsverket [Swedish National Food Agency]. Råd om mat för barn 0–5 år. Hanteringsrapport som beskriver hur risk och nyttovärderingar, tillsammans med andra faktorer, har lett fram till livsmedelsverkets råd. In English: [Advice on food for children 0–5 years. Management report that describes how risk and utility valuations, together with other factors, have led to the Swedish National Food Agency’s advice.]. 2011. Contract No.: 22-2011. Livsmedelsverket, Uppsala.
73.	Spahn JM, Callahan EH, Spill MK, Wong YP, Benjamin-Neelon SE, Birch L, et al. Influence of maternal diet on flavor transfer to amniotic fluid and breast milk and children’s responses: a systematic review. Am J Clin Nutr 2019; 109: 1003s–26s. doi: 10.1093/ajcn/nqy240
74.	Ventura AK, Phelan S, Garcia KS. Maternal diet during pregnancy and lactation and child food preferences, dietary patterns, and weight outcomes: a review of recent research. Curr Nutr Rep 2021; 10(4): 413–26.
75.	Willett W, Rockstrom J, Loken B, Springmann M, Lang T, Vermeulen S, et al. Food in the anthropocene: the EAT-Lancet Commission on healthy diets from sustainable food systems. Lancet 2019; 393(10170): 447–92. doi: 10.1016/S0140-6736(18)31788-4
76.	Nekitsing C, Hetherington MM. Implementing a ‘vegetables first’ approach to complementary feeding. Curr Nutr Rep 2022; 11: 301–10. doi: 10.1007/s13668-022-00399-z
77.	Beauchamp GK, Mennella JA. Flavor perception in human infants: development and functional significance. Digestion 2011; 83: 1–6. doi: 10.1159/000323397
78.	Stein LJ, Cowart BJ, Beauchamp GK. The development of salty taste acceptance is related to dietary experience in human infants: a prospective study. Am J Clin Nutr 2012; 95(1): 123–9.
79.	Deren K, Weghuber D, Caroli M, Koletzko B, Thivel D, Frelut ML, et al. Consumption of sugar-sweetened beverages in paediatric age: a position paper of the European Academy of Paediatrics and the European Childhood Obesity Group. Ann Nutr Metab 2019; 74(4): 296–302. doi: 10.1159/000499828
80.	Hofman A, Hazebroek A, Valkenburg HA. A randomized trial of sodium intake and blood pressure in newborn infants. JAMA 1983; 250(3): 370–3. doi: 10.1001/jama.1983.03340030030023
81.	Whelton PK, Carey RM, Aronow WS, Casey DE, Jr., Collins KJ, Dennison Himmelfarb C, et al. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APHA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Hypertension 2018; 71(6): e13–115. doi: 10.1161/HYP.0000000000000065
82.	Johansson U, Ohlund I, Hernell O, Lonnerdal B, Lindberg L, Lind T. Protein-reduced complementary foods based on Nordic ingredients combined with systematic introduction of taste portions increase intake of fruits and vegetables in 9 month old infants: a randomised controlled trial. Nutrients 2019; 11(6): 1255. doi: 10.3390/nu11061255
83.	Marlier L, Schaal B, Soussignan R. Neonatal responsiveness to the odor of amniotic and lacteal fluids: a test of perinatal chemosensory continuity. Child Dev 1998; 69(3): 611–23.
84.	Mennella JA, Lukasewycz LD, Castor SM, Beauchamp GK. The timing and duration of a sensitive period in human flavor learning: a randomized trial. Am J Clin Nutr 2011; 93(5): 1019–24. doi: 10.3945/ajcn.110.003541
85.	Mennella JA, Beauchamp GK. Developmental changes in the acceptance of protein hydrolysate formula. J Dev Behav Pediatr 1996; 17(6): 386–91. doi: 10.1097/00004703-199612000-00003
86.	Virtanen S, Erkkola M, Tuovi H, Heikkinen T, Isolauri E, Kalavainen M, et al. Eating together – food recommendations for families with children. Terveyden Ja Hyvinvoinnin Laitos [National Institute for Health and Welfare, Finland] Helsinki. 2015.
87.	Embætti landlæknis, Island [Directorate of Health, Iceland] and þróunarmiðstöð íslenskrar [Primary Health Care in Iceland]. Næring ungbarna_heilbrigðisstarfsfólk. [Infant nutrition_health care professionals.]. Leiðbeiningar um ung- og smábarnavernd [Guidelines for the protection of young people and infants]. Directorate of Health, Reykjavik, Iceland; 2021. Available from: https://island.is/en/nutrition-recommendations.
88.	Stern J, Funkquist EL, Grandahl M. The association between early introduction of tiny tastings of solid foods and duration of breastfeeding. Int Breastfeed J 2023; 18(1): 4. doi: 10.1186/s13006-023-00544-6
89.	Harris G, Mason S. Are there sensitive periods for food acceptance in infancy? Curr Nutr Rep 2017; 6(2): 190–6. doi: 10.1007/s13668-017-0203-0
90.	Coulthard H, Harris G, Emmett P. Delayed introduction of lumpy foods to children during the complementary feeding period affects child’s food acceptance and feeding at 7 years of age. Matern Child Nutr 2009; 5(1): 75–85. doi: 10.1111/j.1740-8709.2008.00153.x
91.	Burggren WW, Mueller CA. Developmental critical windows and sensitive periods as three-dimensional constructs in time and space. Physiol Biochem Zool 2015; 88(2): 91–102. doi: 10.1086/679906
92.	Johnson SL. Developmental and environmental influences on young children’s vegetable preferences and consumption. Adv Nutr 2016; 7(1): 220s–31s. doi: 10.3945/an.115.008706
93.	D’Auria E, Bergamini M, Staiano A, Banderali G, Pendezza E, Penagini F, et al. Baby-led weaning: what a systematic review of the literature adds on. Ital J Pediatr 2018; 44:49.
94.	Melina V, Craig W, Levin S. Position of the academy of nutrition and dietetics: vegetarian diets. J Acad Nutr Diet 2016; 116(12): 1970–80. doi: 10.1016/j.jand.2016.09.025
95.	Sebastiani G, Herranz Barbero A, Borras-Novell C, Casanova MA, Aldecoa-Bilbao V, Andreu-Fernandez V, et al. The effects of vegetarian and vegan diet during pregnancy on the health of mothers and offspring. Nutrients 2019; 11(3): 557. doi: 10.3390/nu11030557
96.	Weder S, Hoffmann M, Becker K, Alexy U, Keller M. Energy, macronutrient intake, and anthropometrics of vegetarian, vegan, and omnivorous children (1–3 years) in Germany (VeChi Diet Study). Nutrients 2019; 11(4): 832. doi: 10.3390/nu11040832
97.	Weder S, Keller M, Fischer M, Becker K, Alexy U. Intake of micronutrients and fatty acids of vegetarian, vegan, and omnivorous children (1–3 years) in Germany (VeChi Diet Study). Eur J Nutr 2022; 61(3): 1507–20. doi: 10.1007/s00394-021-02753-3
98.	Bärebring L, Lamberg-Allardt C, Thorisdottir B, Ramel A, Söderlund F, Arnesen EK, et al. Intake of vitamin B12 in relation to vitamin B12 status in groups susceptible to deficiency: a systematic review. Food Nutr Res 2023; 67: 8626. doi: 10.29219/fnr.v67.8626.
99.	EFSA Panel on Dietetic Products Nutrition and Allergies (EFSA-NDA). Scientific opinion on dietary reference values for carbohydrates and dietary fibre. EFSA J 2010; 8(3): 1462. doi: 10.2903/j.efsa.2010.1462
100.	Pawlak R. To vegan or not to vegan when pregnant, lactating or feeding young children. Eur J Clin Nutr 2017; 71(11): 1259–62. doi: 10.1038/ejcn.2017.111
101.	Niedermaier T, Gredner T, Kuznia S, Schottker B, Mons U, Lakerveld J, et al. Vitamin D food fortification in european countries: the underused potential to prevent cancer deaths. Eur J Epidemiol 2022; 37(4): 309–20. doi: 10.1007/s10654-022-00867-4
102.	Livsmedelsverket. Livsmedelsverkets författningssamling (LIVSFS) 2019:5. Livsmedelsverkets föreskrifter om ändring i Livsmedelsverkets föreskrifter (LIVSFS 2018:5) om berikning av vissa livsmedel. 2019.
103.	Craig WJ, Mangels AR, Fresan U, Marsh K, Miles FL, Saunders AV, et al. The safe and effective use of plant-based diets with guidelines for health professionals. Nutrients 2021; 13(11): 4144. doi: 10.3390/nu13114144
104.	Horta BL, Victora CG, World Health Organization. Short-term effects of breastfeeding: a systematic review on the benefits of breastfeeding on diarrhoea and pneumonia mortality. Geneva: World Health Organization; 2013.
105.	Frank NM, Lynch KF, Uusitalo U, Yang J, Lonnrot M, Virtanen SM, et al. The relationship between breastfeeding and reported respiratory and gastrointestinal infection rates in young children. BMC Pediatr 2019; 19(1): 339. doi: 10.1186/s12887-019-1693-2
106.	Horta BL, Rollins N, Dias MS, Garcez V, Perez-Escamilla R. Systematic review and meta-analysis of breastfeeding and later overweight or obesity expands on previous study for World Health Organization. Acta Paediatr 2023; 112(1): 34–41. doi: 10.1111/apa.16460
107.	Qiao J, Dai LJ, Zhang Q, Ouyang YQ. A meta-analysis of the association between breastfeeding and early childhood obesity. J Pediatr Nurs 2020; 53: 57–66. doi: 10.1016/j.pedn.2020.04.024
108.	Dewey KG, Güngör D, Donovan SM, Madan EM, Venkatramanan S, Davis TA, et al. Breastfeeding and risk of overweight in childhood and beyond: a systematic review with emphasis on sibling-pair and intervention studies. Am J Clin Nutr 2021; 114(5): 1774–90.
109.	Dewey KG. Growth characteristics of breast-fed compared to formula-fed infants. Biol Neonate 1998; 74(2): 94–105. doi: 10.1159/000014016
110.	Sinkiewicz-Darol E, Adamczyk I, Lubiech K, Pilarska G, Twaruzek M. Leptin in human milk – one of the key regulators of nutritional programming. Molecules 2022; 27(11): 3581. doi: 10.3390/molecules27113581
111.	Gregg B, Ellsworth L, Pavela G, Shah K, Berger PK, Isganaitis E, et al. Bioactive compounds in mothers milk affecting offspring outcomes: a narrative review. Pediatr Obes 2022; 17(7): e12892. doi: 10.1111/ijpo.12892
112.	Koletzko B, Godfrey KM, Poston L, Szajewska H, van Goudoever JB, de Waard M, et al. Nutrition during pregnancy, lactation and early childhood and its implications for maternal and long-term child health: the Early Nutrition Project Recommendations. Ann Nutr Metab 2019; 74(2): 93–106.
113.	Marousez L, Lesage J, Eberle D. Epigenetics: linking early postnatal nutrition to obesity programming? Nutrients 2019; 11(12): 2966. doi: 10.3390/nu11122966
114.	WHO Multicentre Growth Reference Study Group. WHO child growth standards based on length/height, weight and age. Acta Paediatrica Suppl 2006; 450: 76–85.
115.	Güngör D, Nadaud P, LaPergola CC, Dreibelbis C, Wong YP, Terry N, et al. Infant milk-feeding practices and cardiovascular disease outcomes in offspring: a systematic review. Am J Clin Nutr 2019; 109: 800s–16s. doi: 10.1093/ajcn/nqy332
116.	Lampousi AM, Carlsson S, Lofvenborg JE. Dietary factors and risk of islet autoimmunity and type 1 diabetes: a systematic review and meta-analysis. EBioMedicine 2021; 72: 103633.
117.	de Silva D, Halken S, Singh C, Muraro A, Angier E, Arasi S, et al. Preventing food allergy in infancy and childhood: systematic review of randomised controlled trials. Pediatr Allergy Immunol 2020; 31(7): 813–26. doi: 10.1111/pai.13273
118.	Koletzko B. Human milk lipids. Ann Nutr Metab 2016; 69 Suppl 2: 28–40.
119.	Obbagy JE, English LK, Wong YP, Butte NF, Dewey KG, Fleischer DM, et al. Complementary feeding and food allergy, atopic dermatitis/eczema, asthma, and allergic rhinitis: a systematic review. Am J Clin Nutr 2019; 109(Suppl_7): 890S–934S. doi: 10.1093/ajcn/nqy220
120.	Oddy WH, Robinson M, Kendall GE, Li J, Zubrick SR, Stanley FJ. Breastfeeding and early child development: a prospective cohort study. Acta Paediatr 2011; 100(7): 992–9. doi: 10.1111/j.1651-2227.2011.02199.x
121.	Powell-Wiley TM, Poirier P, Burke LE, Despres JP, Gordon-Larsen P, Lavie CJ, et al. Obesity and cardiovascular disease: a scientific statement from the American Heart Association. Circulation 2021; 143(21): e984–1010.
122.	Strøm M, Mortensen EL, Kesmodel US, Halldorsson T, Olsen J, Olsen SF. Is breast feeding associated with offspring IQ at age 5? Findings from prospective cohort: lifestyle During Pregnancy Study. BMJ Open 2019; 9(5): e023134. doi: 10.1136/bmjopen-2018-023134.
123.	Umer A, Hamilton C, Edwards RA, Cottrell L, Giacobbi P, Innes K, et al. Association between breastfeeding and childhood cardiovascular disease risk factors. Matern Child Health J 2019; 23(2): 228–39. doi: 10.1007/s10995-018-2641-8
124.	Conway MC, McSorley EM, Mulhern MS, Strain JJ, van Wijngaarden E, Yeates AJ. Influence of fatty acid desaturase (FADS) genotype on maternal and child polyunsaturated fatty acids (PUFA) status and child health outcomes: a systematic review. Nutr Rev 2020; 78(8): 627–46.
125.	Horta BL, Loret de Mola C, Victora CG. Breastfeeding and intelligence: a systematic review and meta-analysis. Acta Paediatr 2015; 104: 14–19. doi: 10.1111/apa.13139
126.	Kramer MS, Aboud F, Mironova E, Vanilovich I, Platt RW, Matush L, et al. Breastfeeding and child cognitive development: new evidence from a large randomized trial. Arch Gen Psychiatry 2008; 65(5): 578–84.
127.	Kramer MS, Matush L, Bogdanovich N, Aboud F, Mazer B, Fombonne E, et al. Health and development outcomes in 6.5-y-old children breastfed exclusively for 3 or 6 mo. Am J Clin Nutr 2009; 90(4): 1070–4. doi: 10.3945/ajcn.2009.28021
128.	Nevins JEH, Donovan SM, Snetselaar L, Dewey KG, Novotny R, Stang J, et al. Omega-3 fatty acid dietary supplements consumed during pregnancy and lactation and child neurodevelopment: a systematic review. J Nutr 2021; 151(11): 3483–94.
129.	Du Toit G, Roberts G, Sayre PH, Bahnson HT, Radulovic S, Santos AF, et al. Randomized trial of peanut consumption in infants at risk for peanut allergy. N Engl J Med 2015; 372(9): 803–13. doi: 10.1056/NEJMoa1414850
130.	Logan K, Bahnson HT, Ylescupidez A, Beyer K, Bellach J, Campbell DE, et al. Early introduction of peanut reduces peanut allergy across risk groups in pooled and causal inference analyses. Allergy 2022; 00:1–12. doi: 10.1111/all.15597
131.	Perkin MR, Logan K, Tseng A, Raji B, Ayis S, Peacock J, et al. Randomized trial of introduction of allergenic foods in breast-fed infants. N Engl J Med 2016; 374(18): 1733–43. doi: 10.1056/NEJMoa1514210
132.	Skjerven HO, Lie A, Vettukattil R, Rehbinder EM, LeBlanc M, Asarnoj A, et al. Early food intervention and skin emollients to prevent food allergy in young children (PreventADALL): a factorial, multicentre, cluster-randomised trial. Lancet 2022; 399(10344): 2398–411. doi: 10.1016/S0140-6736(22)00687-0
133.	Berti C, Agostoni C, Davanzo R, Hypponen E, Isolauri E, Meltzer HM, et al. Early-life nutritional exposures and lifelong health: immediate and long-lasting impacts of probiotics, vitamin D, and breastfeeding. Nutr Rev 2017; 75(2): 83–97. doi: 10.1093/nutrit/nuw056
134.	Szajewska H, Shamir R, Chmielewska A, Pieścik-Lech M, Auricchio R, Ivarsson A, et al. Systematic review with meta-analysis: early infant feeding and coeliac disease – update 2015. Aliment Pharmacol Ther 2015; 41(11): 1038–54. doi: 10.1111/apt.13163
135.	Güngör D, Nadaud P, LaPergola CC, Dreibelbis C, Wong YP, Terry N, et al. Infant milk-feeding practices and diabetes outcomes in offspring: a systematic review. Am J Clin Nutr 2019; 109(Suppl_7): 817S–37S. doi: 10.1093/ajcn/nqy311
136.	Bonifacino E, Schwartz EB, Jun H, Wessel CB, Corbelli JA. Effect of lactation on maternal hypertension: a systematic review. Breastfeed Med 2018; 13(9): 578–88. doi: 10.1089/bfm.2018.0108