Scientists from several medical facilities in the United States and Europe have applied a computer model to predict how homocysteine-lowering vitamin therapy might be used to reduce the incidence of heart disease. Their assessment appeared in a recent issue of the Journal of the American Medical Association.

The purpose of the analysis was to estimate what effect consumption of folic acid-fortified grain foods is likely to have on the incidence of coronary heart disease (CHD) in the United States through the end of this decade. The researchers also used the model to estimate what additional benefits might accrue from the prophylactic use of folic acid and B12 supplements by certain groups of people.

Vitamins likely to make a difference

Using current U.S. food intake information, the model predicted that consumption of grain foods fortified with folic acid would result in a 13% reduction in myocardial infarctions in men and an 8% reduction in women. By conservative estimates, that could reduce annual CHD mortality rates in the United States by 1% to 3%.

Further estimates show that if the diets of those with known heart disease were supplemented with 1 mg folic acid and 0.5 mg B12 - with an intent to lower homocysteine - an additional 300,000 fewer CHD deaths would occur over a 10-year period.

Who benefits most?

One function of this computer model was to weigh the costs of homocysteine screening and vitamin therapy against the long-term financial burden of treating those with heart disease. According to this analysis, it is not cost effective to screen everyone for homocysteine. The best strategy, say the researchers, is to screen all men over age 45 and treat those with homocysteine levels greater than 10 micromoles/liter. The model also demonstrated the cost-effectiveness of screening and treating women over age 55, which supports the fact that heart disease becomes a more critical problem once women reach menopause.

Picture is still incomplete

The authors of this study admit that the major limitation in their prediction model is the lack of decisive clinical evidence that lowered homocysteine levels will result in a reduced incidence of heart disease. They know that elevated homocysteine has been linked to heart disease. They also know that serum homocysteine can be lowered with therapeutic doses of folic acid and B12. (Based on a literature review, the researchers estimated that supplementation with 1 mg folic acid and 0.5 mg B12 would lower serum homocysteine levels by 33% in those with starting levels of 12 micromoles/liter.)

What is still unclear is whether elevated homocysteine is a cause of heart disease, or is the result of damage already done. This question of cause-or-effect is what is holding up some scientists' decision on whether or not to recommend routine homocysteine testing as a standard procedure for all those at risk for heart disease.

While this question remains to be answered, the authors of this study point out that vitamin therapy is inexpensive and well tolerated. They suggest that health professionals consider folic acid and B12 supplementation for men over age 45 and women over age 55 as a cost effective way to lessen the burden caused by heart disease.