Heart Disease Prevention

What Is the Scientific Evidence for B Vitamins?

The Framingham Heart Study, one of the classic gold mines of heart-related health information, found an important link: If your intake of B6, folate, or B12 is low, your homocysteine levels are likely to be high. Furthermore, about two-thirds of the people studied were not getting enough B6 or folate in their diet. (B12 deficiency is much less common.)

Other studies have found that supplementation with folate and vitamin B6, alone or in combination with each other, lowers homocysteine levels. Vitamin B12 supplementation also appears to help. One clinical trial found that B-vitamin supplementation in men with moderately high homocysteine levels reduced these levels by more than half. In this particular study, the doses used were well above nutritional doses: folate (1,000 mcg), vitamin B6 (10 mg), and vitamin B12 (50 mcg).

However, as mentioned Homocysteine and Heart Disease, we don't know for sure that high homocysteine levels cause heart disease, so these findings can't be taken as proof that supplemental B vitamins will protect against heart disease.

We do know that low blood levels of folate and vitamin B6 have been linked to an increased risk of heart disease. But just because people with heart disease have low levels of folate and B6 doesn't mean that taking extra folate and B6 will help. It is always possible that heart disease causes the vitamin deficiency, rather than the reverse.

What we really need are some intervention trials where people are given B6 and folate or placebo, and the rate of heart disease is evaluated. Such clinical trials are currently underway. At the present time, the best evidence we have comes from an observation study, the Nurses' Health Study. (That large study of 121,700 female nurses ages 30 to 55 began in 1976. Like the Framingham study, it has provided a mother lode of valuable health information.)

The study, published in the February 4, 1998, issue of the Journal of the American Medical Association, examined data on 80,000 of the women in the Nurses' Health Study who had no history of heart disease. Researchers looked at their intake of folate and vitamin B6 to check for a possible connection between that and the development of heart disease.

Vitamin intake from both diet and multivitamin supplementation was considered. It was found that women with the highest folate intake had half the risk of heart disease compared to those with the lowest intake, and that each 100 mcg/day increase in intake lowered the risk by 5.8%. Positive results were also seen with vitamin B6 intake—in this case, each 2 mg/day increase in intake lowered the risk by 17%. The routine use of multiple vitamins in supplement form reduced the risk of heart disease by 24%.

Additionally, women who got at least 400 mcg/day of folate and 3 mg/day of vitamin B6 were significantly less likely to suffer heart attacks compared to those who got much lower amounts. Researchers concluded that higher intake of folate, either alone or in combination with vitamin B6, significantly reduced the risk of heart disease and heart attack in women.

These results are impressive and are an important addition to our store of information, but we must consider the observational nature of this study. The data on vitamin intake used by the researchers came from questionnaires on health and lifestyle filled out by the nurses over the course of several years. As with all such studies, there is no way to know whether some unidentified factor may have played a role in the results.

The positive finding for vitamin B6 takes on even more meaning in light of the study discussed in Homocysteine and Heart Disease. That study suggested that vitamin B6 levels may be more important than homocysteine levels as a risk factor for heart disease. Clearly, there is more work to be done to accurately nail down the interplay between levels of homocysteine, B vitamins, and heart disease.

Despite the fact that the evidence is not yet set in stone, it certainly makes sense to get enough B6, B12, and folate in your diet anyway. A multivitamin supplement might typically provide 400 mcg of folate, 2 mg of vitamin B6, and 6 mcg of vitamin B12. This may be all the protection most people need.