Low-dose folic acid supplementation does not influence plasma methionine concentrations in young non-pregnant women

An elevated plasma total homocysteine (tHcy) concentration is a risk factor for cardiovascular disease and for having offspring with a neural-tube defect. Folate is a methyl donor in the remethylation of homocysteine into methionine. Although folic acid supplementation decreases tHcy concentrations, effects of folic acid supplementation on plasma methionine concentrations are unclear. There is also concern that folic acid supplementation negatively affects vitamin B-12 status. We studied effects of low-dose folic acid supplementation on methionine and vitamin B-12 concentrations in plasma. We also investigated whether baseline plasma methionine and tHcy concentrations correlated with the baseline folate and vitamin B-12 status. For a period of 4 weeks, 144 young women received either 500 mu g folic acid each day, or 500 mu g folic acid and placebo tablets on alternate days, or a placebo tablet each day. Plasma methionine, tHcy and plasma vitamin B-12 concentrations were measured at start and end of the intervention period. Folic acid supplementation had no effect on plasma methionine or plasma vitamin B-12 concentrations although it significantly decreased tHcy concentrations. Plasma methionine concentrations showed no correlation with either tHcy concentrations (Spearman r(s)-0.01, P=0.89), or any of the blood vitamin variables at baseline. Baseline tHcy concentrations showed a slight inverse correlation with baseline concentrations of plasma vitamin B-12 (r(s) - 0.25, P < 0.001), plasma folate (r(s) - 0.24, P < 0.01) and erythrocyte folate (r(s) - 0.19, P < 0.05). Tn conclusion, low-dose folic acid supplementation did not influence plasma methionine or plasma vitamin B-12 concentrations. Furthermore, no correlation between plasma methionine concentrations and the blood folate and vitamin B-12 status was shown.