Folate bioavailability in humans: effects of wheat bran and beans

Abstract

The effect of wheat bran or California small white beans in the diet on absorption of monoglutamyl (PteGlu) and heptaglutamyl folic acid (PteGlu7) was studied in six men confined to a metabolic unit. Relative folate absorption was determined by measuring 24-h urinary folate excretion and serum folate levels at 0, 1, and 2 h after ingestion of a formula meal containing 1.13 mumol PteGlu or PteGlu7 (500 micrograms PteGlu equivalent). Serum data showed PteGlu absorption was more rapid than PteGlu7 absorption. Urinary excretion of PteGlu7 was 63% (50 less than or equal to mean less than or equal to 76%) of PteGlu excretion. Addition of 30 g wheat bran to the formula meal accelerated PteGlu absorption whereas PteGlu7 absorption was not significantly affected by either food. Effects of the two foods were qualitatively different. Wheat bran increased the absorption of PteGlu relative to PteGlu7 whereas beans minimized the difference between PteGlu and PteGlu7 serum areas.