The short-term bioavailability of microencapsulated folic acid and L-5-methyl-tetrahydrofolate

Background: Folic acid (FA) is added to grain products in Canada to reduce the incidence of neural tube defects. There have been concerns that FA fortification may have adverse effects on the population. L-5-methyltetrahydrofolate (L-5-methyl-THF) is an alternative form of folate and may be safer than FA. However, L-5-methyl-THF has poor stability relative to FA limiting its use as a food fortificant. Microencapsulation of L-5-methyl-THF in a polyglycerol monostearate coating could improve its stability in food matrices. Objective: To determine if microencapsulated FA and L-5-methyl-THF, either in capsule form or in skim milk powder, increases plasma folate concentrations over 8 hours, to the same extent, compared to free-form FA and L-5-methyl-THF. Methods: In a repeated-measures crossover design, participants (n=15) were randomly administered seven treatments as single doses. The doses were based on the molar equivalent of 400 μg of FA. Treatments included: placebo, FA, microencapsulated FA, L-5-methyl-THF, microencapsulated L-5-methyl-THF, microencapsulated FA in milk powder, and microencapsulated L-5-methyl-THF in milk powder. Blood was collected at baseline and at frequent intervals over the 8-hour test period. Plasma folate was quantified at each time point and corrected to baseline values. Area under the curve(AUC)was calculated for each treatment and differences between treatments were evaluated using repeated-measures ANOVA. Results: The AUC values (± SEM) for all six folate treatments were significantly greater than the placebo (P<0.05). AUC for L-5-methyl-THF was greater than FA (347±35 vs. 181±12 8h.nmol/L; P<0.001). The AUC for microencapsulated FA was not different than FA (222±12 vs. 181±14 8h.nmol/L; P=0.12). However, the AUC was less for microencapsulated L-5-methyl-THF than L-5-methyl-THF (147±17 vs 347±35 8h.nmol/L; P<0.001). The AUC for microencapsulated FA in milk powder was less than microencapsulated FA (120±11 vs. 222±12 8h.nmol/L; P