A human model to determine folate bioavailability from food: a pilot study for evaluation

Abstract

Background: Knowledge about folate bioavailability from food is essential for the estimation of dietary requirements. Yet, there is a lack of data obtained from validated human studies performed with physiological folate doses. Objective: In this pilot study, a new model for the determination of folate absorption is developed and validated. Design: Under strictly standardized procedures, two healthy ileostomy volunteers consumed single portions of test foods or an oral dose of a pharmaceutical folate preparation of the natural folate diastereomer (6S)-5- methyltetrahydrofolate. Relative folate absorption from oral doses versus an intramuscular injection of the same pharmaceutical preparation was determined using postdose plasma folate concentration curves. Nonabsorbed folate was estimated by postdose folate excretion into stomal effluent. Results: Estimated by plasma areas under the curve, relative folate absorption ranged from 47 to 67% for oral doses from the te st foods strawberries and broccoli and the pharmaceutical (6S)-5-methyltetrahydrofolate preparation. During 10 h postdose, 19-44% of the dietary folate was excreted with the stomal effluent. Varying gut passage times were observed for different food matrices by determining ileostomal folate excretion in 2 h intervals. Around 90% of the folate from the oral doses was recovered in the collected body fluids, plasma and stomal effluent, by 10 h postdose, independent of the size of the administered folate doses of 200 or 400 mg (0.4 or 0.9 mmol). Conclusion: The results imply that this model provides a suitable tool to estimate folate bioavailability from foods. Keywords: Folate absorption; folate in ileostomal effluent; ileostomists; plasma folate kinetics; urinary folate excretion