Effect of homocysteine-lowering nutrients on blood lipids: results from four randomised, placebo-controlled studies in healthy humans.
BACKGROUND
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.


RESULTS
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.


CONCLUSIONS
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.
Olthof
Margreet R
MR
Wageningen Centre for Food Sciences, Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands. margreet.olthof@wur.nl
van Vliet
Trinette
T
Verhoef
Petra
P
Zock
Peter L
PL
Katan
Martijn B
MB
D000328:Adult; D000368:Aged; D001622:Betaine / Q000494:pharmacology* / Q000627:therapeutic use; D002318:Cardiovascular Diseases / Q000517:prevention & control; D005260:Female; D005492:Folic Acid / Q000494:pharmacology; D006710:Homocysteine / Q000097:blood* / Q000187:drug effects; D006801:Humans; D008055:Lipids / Q000097:blood*; D008082:Lipotropic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D010713:Phosphatidylcholines / Q000494:pharmacology* / Q000627:therapeutic use; D010919:Placebos; D012307:Risk Factors
D008055:Lipids; D008082:Lipotropic Agents; D010713:Phosphatidylcholines; D010919:Placebos; D006710:Homocysteine; D001622:Betaine; D005492:Folic Acid