New trial questions B-vitamins for CVD in high-risk women
cardiovascular disease, say the results of the US-based Women's
Antioxidant and Folic Acid Cardiovascular Study (WAFACS) - findings
that cannot be applied to the general population.
But the study focused on women who either had a history of CVD or were considered at high risk due to three or more CVD risk factors such as high blood pressure, high cholesterol levels, diabetes and smoking.
The results, presented at the American Heart Association's Scientific Sessions 2006, go against epidemiological studies that have linked increased blood levels of the amino acid homocysteine to an increased risk of cardiovascular disease (CVD). It has been suggested that by lowering the levels of homocysteine in the blood with B-vitamins, people could cut the risk of CVD.
The WAFACS do agree with two studies published earlier this year. The Heart Outcomes Prevention Evaluation (HOPE) 2 trial and the Norwegian Vitamin (NORVIT) trial reported that B-vitamin supplements did lower homocysteine levels but did not reduce the risk of heart disease, heart attack or stroke for high-risk patients (New England Journal of Medicine).
Again, these studies were focussed on high-risk heart patients and could not be extended to the general population.
The WAFACS conclusions are based on results from a randomized, placebo-controlled study of folic acid and other B vitamins in a subset of 5,442 women participating in a larger trial called Women's Antioxidant Cardiovascular Study (WACS). Participants were health professionals over age 40 who either had a history of CVD or were considered at high risk due to three or more CVD risk factors such as high blood pressure, high cholesterol levels, diabetes and smoking.
Lead author of the study, Christine Albert, from Brigham and Women's Hospital in Boston, compared the effects of a combination of folic acid (2.5 milligrams daily), vitamin B6 (50 mg daily) and vitamin B12 (1 mg daily) versus placebo in reducing risk of major vascular events including coronary heart disease, heart attack and stroke.
After 7.3 years of follow-up, Albert and her co-workers told attendees at the Scientific Session that there were no significant differences between B-vitamin supplemented groups and placebo in terms of the incidence of heart attacks, strokes, coronary revascularization procedures and cardiovascular-related deaths.
"Our study does not suggest that taking folic acid, B6 or B12 primarily to prevent cardiovascular disease (CVD) would be worthwhile. Women who are taking them solely for that purpose may want to discontinue," said Albert.
In addition, Albert did say that the study does appear to support that homocysteine is a risk factor or a marker of pre-existing cardiovascular disease.
While the researchers reported a null-result for this high-risk population group, the safety of the vitamins did receive a boost with no adverse effects being reported.
They also stressed the importance of the vitamins for non-cardiac reasons, particularly folic acid supplementation for women of childbearing age to reduce birth defects of the brain and spinal cord.
The positive safety record and the additional benefits of B-vitamin supplementation was also picked up by the US trade organisation The Council for Responsible Nutrition (CRN).
"It would be a public health disservice if the results of this study were misinterpreted in a manner which discouraged women of childbearing age from heeding the recommendations of the Institute of Medicine and the Centers for Disease Control to supplement their diet with folic acid," said the CRN in a statement.
Dr. Annette Dickinson, consultant and past president, CRN also emphasised that the new trial is one of several that have tested B vitamins in people who were already ill with heart disease.
She also said that, while it would have been exciting if the results had demonstrated B vitamins could either reverse disease or prevent future cardiovascular events, people should not expect nutrients to perform like drugs.
"It is unrealistic to expect vitamins to undo damage caused by heart disease, nor should consumers look to B vitamins to treat disease," said Dr. Dickinson. "The real question should be whether a healthy lifestyle - eating fruits and vegetables, getting exercise, regular physician visits, and consistent use of vitamin supplements - could have prevented these women from getting heart disease in the first place."
"There are numerous observational studies that have shown benefits of B vitamins in reducing cardiovascular risk in healthy populations. That is the hypothesis that science should be testing: whether life-long, generous intake of B vitamins could confer benefit in primary prevention of cardiovascular disease," she said.
The WAFACS study was funded by the National Heart, Lung, and Blood Institute (NHLBI).