Brouwer I A, van Dusseldorp M, Duran M, Thomas C M, Hautvast J G, Eskes T K, Steegers-Theunissen R P
Division of Human Nutrition and Epidemiology, Wageningen Agricultural University, The Netherlands.
Br J Nutr. 1999 Aug;82(2):85-9. doi: 10.1017/s0007114599001221.
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 B12 status. We studied effects of low-dose folic acid supplementation on methionine and vitamin B12 concentrations in plasma. We also investigated whether baseline plasma methionine and tHcy concentrations correlated with the baseline folate and vitamin B12 status. For a period of 4 weeks, 144 young women received either 500 micrograms folic acid each day, or 500 micrograms folic acid and placebo tablets on alternate days, or a placebo tablet each day. Plasma methionine, tHcy and plasma vitamin B12 concentrations were measured at start and end of the intervention period. Folic acid supplementation had no effect on plasma methionine or plasma vitamin B12 concentrations although it significantly decreased tHcy concentrations. Plasma methionine concentrations showed no correlation with either tHcy concentrations (Spearman rs-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 B12 (rs-0.25, P < 0.001), plasma folate (rs-0.24, P < 0.01) and erythrocyte folate (rs-0.19, P < 0.05). In conclusion, low-dose folic acid supplementation did not influence plasma methionine or plasma vitamin B12 concentrations. Furthermore, no correlation between plasma methionine concentrations and the blood folate and vitamin B12 status was shown.
血浆总同型半胱氨酸（tHcy）浓度升高是心血管疾病以及生育患有神经管缺陷后代的一个风险因素。叶酸是同型半胱氨酸再甲基化生成甲硫氨酸过程中的甲基供体。尽管补充叶酸可降低tHcy浓度，但补充叶酸对血浆甲硫氨酸浓度的影响尚不清楚。此外，人们还担心补充叶酸会对维生素B12状态产生负面影响。我们研究了低剂量补充叶酸对血浆中甲硫氨酸和维生素B12浓度的影响。我们还调查了血浆甲硫氨酸和tHcy的基线浓度与叶酸和维生素B12的基线状态是否相关。在4周的时间里，144名年轻女性分别接受每日500微克叶酸、隔天500微克叶酸加安慰剂片或每日一片安慰剂。在干预期开始和结束时测量血浆甲硫氨酸、tHcy和血浆维生素B12浓度。补充叶酸对血浆甲硫氨酸或血浆维生素B12浓度没有影响，尽管它显著降低了tHcy浓度。血浆甲硫氨酸浓度与tHcy浓度（Spearman秩相关系数rs = -0.01，P = 0.89）或基线时任何血液维生素变量均无相关性。基线tHcy浓度与血浆维生素B12的基线浓度（rs = -0.25，P < 0.001）、血浆叶酸（rs = -0.24，P < 0.01）和红细胞叶酸（rs = -0.19，P < 0.05）呈轻度负相关。总之，低剂量补充叶酸不会影响血浆甲硫氨酸或血浆维生素B12浓度。此外，血浆甲硫氨酸浓度与血液叶酸和维生素B12状态之间未显示出相关性。
