One year B-vitamins increases serum and whole blood folate forms and lowers plasma homocysteine in older Germans

Background: We aimed to study the effect of long-term supplementation of B-vitamins on folate forms in serum and whole blood (WB) in elderly German subjects. Methods: 59 participants (mean age 67 years) were randomized to daily receive either vitamin D-3 (1200 IU), folic acid (500 mu g), vitamin B-12 (500 mu g), vitamin B-6 (50 mg), and calcium carbonate (456 mg) or vitamin D-3 plus calcium carbonate. Serum and WB folate forms were measured before and after 6 and 12 months. Results: B-vitamins supplementation for 6 months led to higher concentrations of 5-methyltetrahydrofolate (5-methylTHF) in serum (mean 49.1 vs. 19.6 nmol/L) and WB (1332 vs. 616 nmol/L). Also non-methyl-folate concentrations in serum and WB were higher after 6 months with B-vitamins supplementation. Unmetabolized folic acid (UFA) increased after supplementation. tHcy concentration was lowered after 1 year of B-vitamin supplementation (mean 13.1 vs. 9.6 mu mol/L). A stronger reduction of tHcy after 1 year was found in participants who had baseline level > 12.5 mu mol/L (mean 17.0 vs. 11.9 mu mol/L) compared to those with baseline tHcy lower than this limit (mean 9.1 vs. 7.4 mu mol/L). In contrast, the increases in serum and WB 5-methylTHF were comparable between the two groups. Conclusions: One year B-vitamins supplementation increased the levels of 5-methylTHF and non-methylfolate in serum and WB, normalized tHcy, but caused an increase in the number of cases with detectable UFA in serum. Lowering of tHcy was predicted by baseline tHcy, but not by baseline serum or WB 5-methylTHF.