WASHINGTON, Feb 27, 2007 /PRNewswire-USNewswire via COMTEX/ -- A new
meta-analysis examining the effect of antioxidant supplements on all-cause
mortality published in the Feb. 28, 2007 issue of the Journal of the American
Medical Association (JAMA) misuses meta-analysis methods to create generalized
conclusions that may inappropriately confuse and alarm consumers who can benefit
from supplementing with antioxidants, said the Council for Responsible Nutrition
(CRN), the leading trade association for the dietary supplement industry.
"Healthy consumers can feel confident in continuing to take antioxidants for the
benefits they provide. This meta-analysis does nothing to change those facts,"
said CRN's Andrew Shao, Ph.D., vice president, scientific and regulatory
affairs. "While meta-analyses can be useful when the included studies are very
similar in design and study population, this meta-analysis combined studies that
differ vastly from each other in a number of important ways that compromise the
results."
For example, the meta-analysis included clinical trials that varied widely in
terms of dosage, duration, study population and nutrients tested -- such as data
from a one-day study with a vitamin A dose of 200,000 IU mixed with data from
other studies lasting years. In addition, many of the clinical trials included
in the meta-analysis tested nutrients beyond those that were the focus of the
article (vitamins A, C, and E; beta-carotene; selenium), including lutein and
zinc, making it difficult to appropriately evaluate the contribution of those
trials to the overall meta-analysis.
"It's like comparing apples and oranges," said Dr. Shao.
Moreover, the overwhelming majority of the clinical trials included in the
meta-analysis tested for secondary prevention, looking at how a nutrient works
in those who already are diseased, instead of primary prevention studies in
healthy populations.
"Combining secondary prevention and primary prevention trials and then making
conclusions for the entire population is an unsound scientific approach," said
Dr. Shao. "Additionally, many of the treatment trials had limitations, including
the expectation that a simple antioxidant vitamin could be expected to overturn
serious illness, such as cancer or heart disease. These trials likely
statistically skewed the results."
Dr. Shao further pointed out, "The study authors concluded that overall there
was no effect of antioxidant supplements on all-cause mortality. It was only
after the researchers divided the chosen clinical trials into 'high risk bias'
and 'low risk bias' groups, using their own criteria, that they observed a
statistically significant effect on mortality. This meta-analysis appears to be
a predetermined conclusion in search of a method to support it."
The Council for Responsible Nutrition (CRN), founded in 1973, is a Washington,
D.C.-based trade association representing dietary supplement industry ingredient
suppliers and manufacturers. CRN members voluntarily adhere to a strong code of
ethics, comply with dosage limits and manufacture dietary supplements to high
quality standards under good manufacturing practices. For more information visit
the CRN website http://www.crnusa.org.
SOURCE Council for Responsible Nutrition
CONTACT: Judy Blatman, +1-202-204-7962, or Gretchen Powers, +1-202-776-7925, both of the
Council for Responsible Nutrition
URL: http://www.crnusa.org
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