By David Michaels

This is how it always works. A leading medical journal publishes a study saying a commercial product may be dangerous, perhaps even killing people. The trade association representing the manufacturers quickly attacks the study (preferably in the same news cycle), accusing the scientists of incompetence or worse.

The latest issue of the Journal of The American Medical Association (JAMA) includes a study that links that use of antioxidants (beta carotene, vitamin A, and vitamin E) with increased mortality. The issue was published today. Yesterday, the Council for Responsible Nutrition, the diet supplement industry’s trade association, issued a scathing press release, calling the study “muddled” and based on an “unsound scientific approach.”

The press release worked. The press coverage of the JAMA article included the trade association’s disparaging comments. The Washington Post quotes the Council for Responsible Nutrition’s Andrew Shao: “The message to the average consumer is: Don’t pay attention to this. This doesn’t apply to you.”

What the trade association is doing here is what I’ve called manufacturing uncertainty. The associations say scientists don’t agree, so there is no reason to limit intake of what may be dangerous amounts of drugs. It’s a public relations trick used most widely by the tobacco industry, but also by many, many polluters and producers of dangerous chemicals.

The JAMA paper examined the results of 68 randomized trials of dietary supplements, involving 232,000 participants. The authors found that, in the trials with strongest methods (47 trials involving 180,938 subjects), antioxidants were associated with significantly increased mortality risk. This is consistent with the evidence to date. There have been several clinical trials that found antioxidants, especially beta-carotene, increased lung cancer risk; there is little human evidence that they reduce cancer risk. The JAMA paper is a systematic compilation and synthesis of data from previously published papers.

The fact that these chemicals don’t prevent cancer has not stopped the diet supplement industry from promoting them widely. The ill-conceived Dietary Supplement Health and Education Act (DSHEA) of 1994 deregulated the marketing of dietary and herbal supplements, much to the detriment of the public’s health.

The press deserves some criticism here, too. The debate over the existence of global warming seems to be over, but until recently virtually every newspaper article describing a scientific paper on the issue included commentary by one of the handful of oil industry supported scientists who insisted the science just wasn’t there.

As long as the press continues to give equal time to both sides of the debate – in this case independent scientists on one side and self-interested producers of potentially dangerous, unregulated chemicals on the other – we can expect to see a confused public and uncontrolled hazardous exposures.

David Michaels heads the Project on Scientific Knowledge and Public Policy (SKAPP) and is Professor and Associate Chairman in the Department of Environmental and Occupational Health, the George Washington University School of Public Health and Health Services.