by Tara Armijo-Prewitt
November 11, 2008 - Large and well-designed studies suggest that the long-suspected anti-cancer
benefits of vitamins and nutritional supplements are an illusion. Prior research—largely funded by
the vitamins and dietary supplements industry—was poorly designed and included relatively few
study participants.
Officials at the US National Institutes of Health (NIH) suspended a $119 million study of the role of
vitamin E and selenium in prostate cancer risk last month, after analysis showed a failure to reduce
cancer risk and a possible trend toward increased diabetes risk among participants assigned to the
selenium-only treatment arm of the study. The study had enrolled 35,000 men ages 50 and older in
the US and Canada, and was scheduled to run through 2011.
Similarly, the longest-running clinical trial of folic acid and other
B vitamins concluded this month that these supplements do
not prevent cancer in women. The seven-year study of 5,442
women was published on November 5 in the Journal of the
American Medical Association (JAMA).
The authors randomly assigned some of the women to take folic acid, vitamin B-6 and vitamin B-12 or
placebo sham vitamins. The trial was “double blind,” meaning that neither the study participants nor
their doctors knew which pills they were taking. Blind placebo-controlled clinical studies are
considered the strongest method for scientifically evaluating the potential benefits of a medicine.
Another recent study showed that vitamin D does not prevent breast cancer, either.
Worse than ineffective?
A comprehensive review of published research conducted earlier this year suggested that vitamins
and nutritional supplements are sometimes worse than ineffective as anti-cancer strategies. In April
an international team conducted a meta-analysis of data from 67 placebo-controlled studies of
antioxidant vitamins and health for the Cochrane Collaborative. They found that supplements do not
reduce the risk of disease or prolong life and that consumption of three antioxidants in particular—
beta-carotene, vitamin A and vitamin E—correlated with shorter life spans.
The Health Food Manufacturers' Association (HFMA) attacked the Cochrane study as incomplete
because only the best-designed studies were included in the meta-analysis. "The paper's
conclusions are drawn on less than 9 percent of available evidence,” states a HFMA press release.
“In no way can this review be considered comprehensive.”
Few researchers joined in that condemnation. The reason Cochrane reviews are taken seriously in
the research community is that they utilize data only from well-designed science, such as blind,
placebo-controlled studies, regardless of whether that research is funded by industry or other
sources.
Canadian authorities ordered a recall for two brands of vitamin C supplements believed to be
contaminated with high levels of vitamin A. Some shipments of New Roots Herbal Vitamin C8 and
Vitazan Professional Vitamin C Advanced Ascorbate were recalled because they are believed to
contain excessive amounts of vitamin A due to manufacturing processes. Excessive vitamin A intake
can cause headaches, fatigue, appetite loss, nausea and diarrhea, and during early pregnancy can
cause severe birth defects.
The recall and recent research cast doubt on claims that dietary supplements are safe and may lead
to renewed calls for increased oversight by the U.S. Food and Drug Administration (FDA).
Past efforts to do so have been vigorously challenged by supplements industry lobbyists.
In 1994, Congress passed the Dietary Supplement Health and Education Act, ostensibly to tighten
FDA regulation of the industry. Critics say the law actually derailed trends toward stronger regulation
that were already under way by the early 1990s, and served to slow stronger regulation. Only last
year in the aftermath of scandals involving dietary supplements containing dangerous amounts of
ephedra and androstenedione, the discovery of undeclared ingredients and false claims on
supplement bottles did the FDA move decisively to enforce new product quality control
manufacturing procedures for dietary supplements.
As a result of the 2007 rules, manufacturers will be required for the first time to identify and test their
products' ingredients.
Claims of vitamins and supplements' anti-cancer power are not the only marketing myths recently
contradicted by scientific studies. Vitamins B-12, B-6 and folic acid also failed to reduce the risk of
heart disease in a separate study published in JAMA this May.
Vitamin D failed to reduce breast cancer risk in a recent study, but other possible benefits of vitamin
D are currently under study by the Cochrane Collaborative.
www.epinews.com
Medical News & Exposé
epi
Under-regulated and Unsafe?
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Vitamin supplements do not prevent cancer, may be unsafe
New findings may renew calls for stricter FDA oversight
Vitamin supplements do not reduce the risk of cancer
or prolong life, suggests new research. Three in
particular—beta-carotene, vitamin A and vitamin E—
may even shorten life spans.
|
Canadian authorities have ordered a recall for two brands
of vitamin C supplements believed to be contaminated
with high levels of vitamin A ...which can cause severe
birth defects.
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