Olthof Margreet R, van Vliet Trinette, Verhoef Petra, Zock Peter L, Katan Martijn B
Wageningen Centre for Food Sciences, Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands.
PLoS Med. 2005 May;2(5):e135. doi: 10.1371/journal.pmed.0020135. Epub 2005 May 31.
Betaine (trimethylglycine) lowers plasma homocysteine, a possible risk factor for cardiovascular disease. However, studies in renal patients and in obese individuals who are on a weight-loss diet suggest that betaine supplementation raises blood cholesterol; data in healthy individuals are lacking. Such an effect on cholesterol would counteract any favourable effect on homocysteine. We therefore investigated the effect of betaine, of its precursor choline in the form of phosphatidylcholine, and of the classical homocysteine-lowering vitamin folic acid on blood lipid concentrations in healthy humans.
We measured blood lipids in four placebo-controlled, randomised intervention studies that examined the effect of betaine (three studies, n = 151), folic acid (two studies, n = 75), and phosphatidylcholine (one study, n = 26) on plasma homocysteine concentrations. We combined blood lipid data from the individual studies and calculated a weighted mean change in blood lipid concentrations relative to placebo. Betaine supplementation (6 g/d) for 6 wk increased blood LDL cholesterol concentrations by 0.36 mmol/l (95% confidence interval: 0.25-0.46), and triacylglycerol concentrations by 0.14 mmol/l (0.04-0.23) relative to placebo. The ratio of total to HDL cholesterol increased by 0.23 (0.14-0.32). Concentrations of HDL cholesterol were not affected. Doses of betaine lower than 6 g/d also raised LDL cholesterol, but these changes were not statistically significant. Further, the effect of betaine on LDL cholesterol was already evident after 2 wk of intervention. Phosphatidylcholine supplementation (providing approximately 2.6 g/d of choline) for 2 wk increased triacylglycerol concentrations by 0.14 mmol/l (0.06-0.21), but did not affect cholesterol concentrations. Folic acid supplementation (0.8 mg/d) had no effect on lipid concentrations.
Betaine supplementation increased blood LDL cholesterol and triacylglycerol concentrations in healthy humans, which agrees with the limited previous data. The adverse effects on blood lipids may undo the potential benefits for cardiovascular health of betaine supplementation through homocysteine lowering. In our study phosphatidylcholine supplementation slightly increased triacylglycerol concentrations in healthy humans. Previous studies of phosphatidylcholine and blood lipids showed no clear effect. Thus the effect of phosphatidylcholine supplementation on blood lipids remains inconclusive, but is probably not large. Folic acid supplementation does not seem to affect blood lipids and therefore remains the preferred treatment for lowering of blood homocysteine concentrations.
甜菜碱（三甲基甘氨酸）可降低血浆同型半胱氨酸水平，而同型半胱氨酸可能是心血管疾病的一个风险因素。然而，针对肾病患者以及采用减肥饮食的肥胖个体的研究表明，补充甜菜碱会使血液胆固醇升高；目前尚缺乏关于健康个体的数据。这种对胆固醇的影响可能会抵消甜菜碱对同型半胱氨酸的任何有益作用。因此，我们研究了甜菜碱、其前体胆碱以磷脂酰胆碱形式以及经典的降低同型半胱氨酸的维生素叶酸对健康人群血脂浓度的影响。
我们在四项安慰剂对照的随机干预研究中测量了血脂，这些研究分别考察了甜菜碱（三项研究，n = 151）、叶酸（两项研究，n = 75）和磷脂酰胆碱（一项研究，n = 26）对血浆同型半胱氨酸浓度的影响。我们汇总了各研究中的血脂数据，并计算了相对于安慰剂的血脂浓度加权平均变化。与安慰剂相比，补充甜菜碱（6 g/天）6周使血液低密度脂蛋白胆固醇浓度升高了0.36 mmol/L（95%置信区间：0.25 - 0.46），三酰甘油浓度升高了0.14 mmol/L（0.04 - 0.23）。总胆固醇与高密度脂蛋白胆固醇的比值升高了(0.23)（0.14 - 0.32）。高密度脂蛋白胆固醇浓度未受影响。低于6 g/天的甜菜碱剂量也会升高低密度脂蛋白胆固醇，但这些变化无统计学意义。此外，干预2周后甜菜碱对低密度脂蛋白胆固醇的影响就已明显。补充磷脂酰胆碱（提供约2.6 g/天的胆碱）2周使三酰甘油浓度升高了0.14 mmol/L（0.06 - 0.21），但未影响胆固醇浓度。补充叶酸（0.8 mg/天）对血脂浓度无影响。
补充甜菜碱会使健康人群的血液低密度脂蛋白胆固醇和三酰甘油浓度升高，这与之前有限的数据一致。对血脂的不良影响可能会抵消补充甜菜碱通过降低同型半胱氨酸对心血管健康带来的潜在益处。在我们的研究中，补充磷脂酰胆碱会使健康人群的三酰甘油浓度略有升高。先前关于磷脂酰胆碱与血脂的研究未显示出明确影响。因此，补充磷脂酰胆碱对血脂的影响尚无定论，但可能不大。补充叶酸似乎不会影响血脂，因此仍是降低血液同型半胱氨酸浓度的首选治疗方法。
