Combs Spouts Off

Last March, I commented on several shoddy studies of nutritional supplements, singling out a calcium / vitamin D study that Life Extension Foundation’s Bill Faloon described as perhaps "one of the most poorly designed studies in the history of modern medicine." Well, the February 28 issue of the Journal of the American Medical Association (JAMA) reports a "meta-analysis" of antioxidants that has to rank pretty high on the list of bogus studies. It purports to demonstrate that there is no health benefit associated with vitamins A, C, and E, beta carotene, and selenium, and that A and E may "significantly increase mortality."

The Linus Pauling Institute at Oregon State University was quick to criticize the study. Its director, Balz Frei, said the meta-analysis had multiple serious flaws:

“This is a flawed analysis of flawed data, and it does little to help us understand the real health effects of antioxidants, whether beneficial or otherwise,” Frei said.
…

The “meta-analysis” published in JAMA, which is a statistical analysis of previously published data, looked at 815 antioxidant trials but included only 68 of them in its analysis, Frei said. And two of the studies excluded – which were published in the Journal of the National Cancer Institute and the prominent British medical journal Lancet – found substantial benefits and reduced mortality from intake of antioxidant supplements.

It’s not as if the researchers conducting this meta-analysis carefully selected the best, most unambiguous 68 trials out of the 815 they considered. Instead, they picked mainly various clinical trials of subjects with existing health problems. Furthermore, these sick subjects were getting a variety of pharmaceutical drugs, other nutrients, or other treatments, thus making any conclusions about the specific nutrients being "meta-analyzed" ambiguous and suspect.

The Council for Responsible Nutrition argued that this study represents a misuse of meta-analysis (emphasis added):

"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. …

200,000 IU of Vitamin A?? According to the NIH Office of Dietary Supplements, the "Tolerable Upper Intake Level" of retinol (vitamin A) is 10,000 IU.

"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."

When it comes to studying nutrients, herbs, and the like, the methodology favored by many mainstream medical researchers seems to be something like this: Give a bunch of people who have, say, heart disease some supplement. If lots of them die, announce that taking the supplement can kill you. If lots of them get well, caution the public that further study is needed. Meanwhile, try to come up with a chemical analogue of the supplement that works about the same, but can be patented and sold as a prescription drug.
 

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