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Folic acid and homocysteine

OXFORD, ENGLAND. Many studies have shown that patients with vascular disease, especially coronary heart disease, have higher blood homocysteine levels than do healthy controls. It is clear that the elevated homocysteine levels precede the onset of disease and is unrelated to other risk factors. Epidemiological studies have shown that a prolonged lowering of homocysteine levels of just 1 micromol/liter (in the range of 10-15 micromol/l) could theoretically result in a 10 per cent reduction in risk. It is known that homocysteine concentrations are inversely proportional to blood levels of folic acid (folate), vitamin B12, and vitamin B6 and that homocysteine levels can be lowered by supplementing with these vitamins. Medical researchers at the Radcliffe Infirmary have reviewed the results of trials aimed at lowering homocysteine levels by vitamin supplementation. The trials involved 1114 people with a mean age of 52 years (23 to 75 years); the average (mean) duration of treatment was six weeks and the median baseline blood concentrations of homocysteine and folate were 11.8 micromol/l and 11.6 nanomol/l respectively. The researchers found that daily supplementation with 0.5-5.0 mg of folic acid reduces homocysteine concentrations by 25 per cent. The reduction was significantly greater among patients with high initial homocysteine levels, but did not seem correlated with the amount of folic acid taken in the range of 0.5 to 5.0 mg. Supplementation with vitamin B12 (0.5 mg/daily on average) lowers homocysteine levels by an additional seven per cent, but no effect was noted for vitamin B6 supplementation with an average (mean) intake of 16.5 mg/daily. The researchers conclude that oral supplementation with at least 0.5 mg of folic acid and 1.0 mg of vitamin B12 on a daily basis would lower homocysteine concentration by 3-4 micromol/l theoretically corresponding to a 30-40 per cent reduction in the risk of developing vascular disease. They recommend that further large scale studies be done to evaluate the efficacy and safety of long term use of folic acid and vitamin B12 as a means of reducing the incidence of vascular disease among high risk subjects.
Lowering blood homocysteine with folic acid based supplements: meta-analysis of randomised trials. British Medical Journal, Vol. 316, March 21, 1998, pp. 894- 98

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