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.1
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.2 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.3 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.4
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.
