British Journal of Nutrition

Research Article

Folate absorption from folate-fortified and processed foods using a human ileostomy model

Cornelia M. Witthöfta1 c1, Karin Arkbågea1, Madelene Johanssona1, Eva Lundina2, Gerd Berglunda3, Jie-Xian Zhanga3, Hans Lennernäsa4 and Jack R. Daintya5

a1 Swedish University of Agricultural Sciences, Department of Food Science, P.O. Box 7051, SE-75007 Uppsala, Sweden

a2 University of Umeå, Department of Medical Biosciences/Pathology, SE-90185 Umeå, Sweden

a3 University of Umeå, Nutritional Research, Department of Public Health and Clinical Medicine, SE-90187 Umeå, Sweden

a4 University of Uppsala, Department of Biopharmaceutics and PharmacokineticsBMCP.O. Box 580SE-75123 Uppsala, Sweden

a5 Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK

Abstract

Data on folate absorption from food from validated human studies using physiological folate doses are still needed to estimate dietary requirements and to formulate recommendations. The aim of the present work was to study the effects from fortified and processed foods on folate absorption in ileostomy volunteers (n 9) using the area under the plasma concentration curve (AUC) and kinetic modelling. Using a standardized single-dose protocol, dairy products fortified with a candidate fortificant (6S)-5-methyltetrahydrofolate ((6S)-5-CH3-H4folate), folic acid-fortified bread and a dessert crème containing natural yeast folate polyglutamates were compared with folate supplements. Absorbed folate was estimated by AUC and a kinetic model, and non-absorbed folate by ileostomal folate excretion. Median apparent absorption from test foods ranged from 55 to 86%. Added folate-binding proteins (FBP) significantly reduced folate absorption from dairy products, as in the absence of FBP, AUC–dose-corrected ratios were increased and ileal folate excretion decreased. After in vivo gastrointestinal passage of dairy products containing FBP, up to 43% of the ingested FBP was found in ileostomal effluent. Folate absorption was similar for (6S)-5-CH3-H4folate fortificant from fermented milk and for folic acid from fortified bread. Folic acid, ingested as food fortificant in bread, was significantly less absorbed compared with an isolated supplement. We conclude that all tested foods were suitable matrices for folate fortification. However, dairy products, fortified with the new candidate fortificant (6S)-5-CH3-H4folate, are suitable if no active FBP is present.

(Received December 16 2004)

(Revised August 29 2005)

(Accepted September 11 2005)

Correspondence:

c1 *Corresponding author: Dr Cornelia M. Witthöft, fax +46 18 67 2995, email Cornelia.Witthoft@lmv.slu.se