Posted by Debbie Luyo on Feb.24, 2009

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Dietary supplements are natural, drug-free products such as vitamins, minerals, herbs, amino acids, and enzymes. Use of dietary supplements is on the rise, and an increasing number of physicians are recommending them to their patients, particularly in cases where dietary deficiencies are suspected. Scientific research into the safety and efficacy of dietary supplements is also increasing, despite the reluctance of some mainstream medical journals to publish data from such studies. Some dietary supplements, including caffeinated beverages, vitamins, and other nutrients do not compete in the marketplace with prescription drugs, and several vitamin brands are manufactured by pharmaceutical companies. Other supplements such as ginkgo, garlic, and ginseng, however, may compete with prescription drugs. Because some mainstream medical journals depend on advertising dollars from pharmaceutical companies, the question of bias is an important one. Researchers at Wake Forest University School of Medicine were the first to study the impact of pharmaceutical advertising on the publication policies of several mainstream medical journals. Data from their study is published in the journal BMC Complementary Medicine.

Advertising has an influence on behavior and the choices people make; and advertising in medical journals targets the doctors who read them. Because advertising can potentially impact the recommendations physicians make to their patients, editors, researchers, and companies who advertise in medical journals are required to disclose conflicts of interest, especially in the case of safety and efficacy studies. For this study, the authors predicted that journals with the largest numbers of pharmaceutical advertisements would contain fewer research articles on drug-free dietary supplements than journals with fewer ads. They also predicted that negative conclusions regarding the safety and efficacy of a particular dietary supplement were more likely to appear in journals with a greater number of ads.

The study compared the number of pharmaceutical ads with the number of articles on dietary supplements in 11 major medical journals. Reviewers examined anywhere between 12 and 52 issues of each journal. In addition, they evaluated conclusions regarding safety and efficacy. The journals were sorted according to the number of pharmaceutical advertisements per issue, and divided into three groups. Journals with the largest number of ads averaged as many as 66 per issue. In the middle group ads ranged between 10.5 and 39.4 ads per issue, and only 0.15 ads per issue in journals with the fewest ads. Three journals devoted to complementary and alternative medicine (CAM) were also examined, and found to contain no pharmaceutical advertising.

As predicted, journals featuring the largest number of pharmaceutical advertisements per issue published fewer articles on dietary supplements than journals in the middle group. Journals in the middle group included fewer articles than journals with the least number of ads. The authors found no relationship between a journal’s impact factor, a measure of influence, and the number of pharmaceutical advertisements found in the journal. Other than vitamin products manufactured by pharmaceutical companies, none of the journals contained ads for dietary supplements.

Reviewers found no published data from clinical trials or cohort studies on dietary supplements in journals with the largest number of pharmaceutical ads. Journals with the most ads were considerably more likely to publish articles concluding that dietary supplements are unsafe or ineffective than journals with fewer ads, while journals with fewer ads had fewer negative conclusions regarding safety or efficacy. CAM journals featured a significantly larger number of original articles that included clinical trial data. However, CAM journals were no less likely to publish negative conclusions than mainstream journals in the middle and lower groups. The majority of articles on dietary supplements covered research on products that do not represent a threat to the prescription drug market. Very few articles could be found on dietary supplements like garlic, ginseng, and echinacea, products which can be used in conjunction with a prescription medication, or even take the place of a drug.

Findings from this study support the authors’ original hypothesis that journals with a greater number of pharmaceutical advertisements publish less research on dietary supplements, while journals containing fewer ads are associated with a greater number of articles. Journals with a greater number of ads publish more articles with negative conclusions than journals with fewer ads. The authors suggest that future research include a larger number of journals, and a greater focus on products that may present a threat to the pharmaceutical industry. Bias in medical research is a serious issue that can affect both doctors and their patients. The results of solid scientific endeavor have little impact if they cannot reach their intended audience. Publication of research based on revenue potential, rather than quality is not only unethical, it is, plain and simple, bad science.

Source:

Kemper, K., Hood, K. Does pharmaceutical advertising affect journal publication about dietary supplements? BMC Complementary and Alternative Medicine

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Posted under Health & Fitness, Supplements.