MONDAY, Oct. 11 (HealthDay News) -- Despite reducing levels of a
protein associated with heart disease, supplements containing the B
vitamin folic acid don't reduce the risk for cardiovascular
disease, death or cancer, according to a new large-scale analysis
of studies on the issue.
Folic acid helps prevent devastating neural tube birth defects
such as spina bifida. Since it also lowers blood levels of the
protein homocysteine, which is linked with heart and blood vessel
disease and other ills, some scientists hoped that the powerful
vitamin might lower the risk of heart disease, stroke or
The current meta-analysis suggests that even taken at high
doses, folic acid supplements don't have that effect.
The report is published in the Oct. 11 issue of the
Archives of Internal Medicine.
"Vitamins are necessary to prevent diseases of deficiency like scurvy and rickets, but more is not necessarily better and may be harmful," said Dr. Jeffrey A. Tice, assistant professor of medicine in residence at the University of California, San Francisco and author of an accompanying journal editorial.
To examine folic acid supplements' possible role in preventing
cancer, heart disease or stroke, a team led by Robert Clarke, from
the University of Oxford in England, collected data on 37,485
people who took part in eight trials comparing the value of folic
acid supplements against placebo. These trials represented all the
large randomized studies available that were designed to lower
plasma homocysteine levels for the prevention of cardiovascular
Over five years, there were 9,326 major coronary events,
including strokes and new heart procedures. In addition, 3,010
patients developed cancer and 5,125 people died, according to the
Even though those taking folic acid saw a 25 percent reduction
in homocysteine levels, they were just as likely to have a heart
attack or stroke as those receiving a placebo. In fact, 24.9
percent of these adverse events were among those taking folic acid
and 24.8 percent were among those receiving placebo, the
There was also no significant difference between the groups in
the likelihood of developing cancer (8.7 percent versus 8.2
percent) or dying (13.8 percent versus 13.6 percent), Clarke's
The researchers acknowledged that some benefit in taking folic
acid might emerge after five years -- the length of the study
period -- but said that was unlikely because most heart-protective
benefits from medications tend to emerge within a few years of
However, the researchers found no harmful effects from taking
folic acid in multivitamin supplements or in folate-fortified
foods. (Because getting enough folic acid before and during
pregnancy prevents most neural tube birth defects, many cereals and
other foods are fortified with folic acid.)
"One-third of adults in the United States and one-quarter of those in the United Kingdom report taking daily multivitamin supplements containing folic acid," the authors write. "Although the lack of any other benefits [other than preventing neural tube defects] is disappointing (albeit fairly definitive), the lack of any significant adverse effects on vascular events, cancer incidence, cancer mortality and overall mortality provides reassurance about the safety of population-wide folic acid fortification," they added.
But, Tice cautioned, high-dose folic acid therapy does not
reduce the risk for strokes, heart attacks or cancer.
He also suggested that consumers be cautious about high-dose
supplements. "High doses of other vitamins with a strong scientific
rationale for long-term health benefits, such as the antioxidants
vitamin E and beta carotene, are now known to be harmful," Tice
"Be wary of the current enthusiasm for vitamin D and omega-3 fatty acids until large randomized studies are completed," he added. "The best way to optimize your health is to exercise regularly, eat a nutritious diet, avoid smoking and maintain a healthy weight."
For more information on folic acid, visit the
U.S. National Library of Medicine.
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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