Harvard Health Letter

In Brief: Homocysteine: Turns out not to B so simple

In Brief

Homocysteine: Turns out not to B so simple

Start with research showing that homocysteine, an amino acid in the blood, is biologically related to the atherosclerotic process that plugs up arteries. Add evidence that people with high homocysteine levels are more likely to have heart attacks or strokes. Consider that the vitamins B6, B12, and folic acid ratchet down homocysteine. The result: A hope that this trio of B vitamins (folic acid is in the B vitamin group) might be an important — and relatively inexpensive — way to gird ourselves against the assault of cardiovascular disease.

That optimism will be much harder to keep afloat after the publication of two large studies in the New England Journal of Medicine in March 2006. In the Norwegian Vitamin Trial, over 3,500 heart attack survivors were randomized to take various combinations of the B vitamins (all three; folic acid and vitamin B12; just vitamin B6) or a placebo and followed for about 3½ years. In the Heart Outcomes Prevention Evaluation 2 study, about 5,500 people with vascular disease or diabetes were randomized to take the three B vitamins or a placebo for five years.

In both studies, the vitamins substantially lowered homocysteine levels, but that reduction didn't translate into the hoped-for result — a reduction in risk for major cardiovascular disease.

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