Reviewed: Kemper KJ, Hood KL. Does pharmaceutical advertising affect journal publication about dietary supplements? BMC Complement Altern Med. 2008;8:11.

The US Food and Drug Administration defines dietary supplements (DS) as “vitamins, minerals, herbs or other botanicals, amino acids, and substances such as enzymes, organ tissues, glandulars, and metabolites.” Because of Americans’ increasing interest in supplements, the National Institutes of Health has funded research to evaluate the safety and effectiveness of DS, resulting in an increasing number of published research papers.

Articles in general medical journals are often cited in professional practice guidelines for clinicians and by the media for dissemination of information to the public. Many medical journals are supported by advertising revenue. Seeking to evaluate the relationship between pharmaceutical advertising and publication about natural health products (which may be viewed as competing with pharmaceutical products), the authors conducted a pilot study to explore this relationship and to compare this to publication about DS in three journals devoted to complementary and alternative medicine (CAM).

The authors hypothesized that journals with more pharmaceutical advertisements (pharmads) would publish fewer articles about DS and more articles suggesting that DS were unsafe or ineffective than would journals with fewer pharmads. Also, they expected that CAM journals would have fewer pharmads and more DS articles and that fewer of the articles in CAM journals would be unfavorable about DS than articles in the general medical journals.

The authors selected 10 major medical journals published in English and devoted to general medicine, internal medicine, or pediatrics: American Family Physician, British Medical Journal, Canadian Medical Association Journal, Journal of the American Medical Association, New England Journal of Medicine, Annals of Internal Medicine, Archives of Internal Medicine, Pediatrics, Archives of Pediatrics and Adolescent Medicine, and Pediatric Research. All issues of each journal for the time period between June 30, 2006, and June 30, 2007, were reviewed.

The review also included three CAM journals published during the same period: Journal of Alternative and Complementary Therapies, Alternative Therapies in Health and Medicine, and Explore.

Between May 21 and July 17, 2007, two premedical students reviewed the journals by using standard rating forms created for this study. They examined each page of every journal reviewed, selecting pages that included any kind of advertising or any report regarding a dietary supplement.

For analytical purposes, the ads were collapsed into two categories: pharmaceutical versus other.

Articles about DS were divided into major articles (original research, editorials, reviews) and other types of articles (basic scientific mechanisms, case reports, letters, fillers, news, abstracts, meeting notes, and similar).

For each DS article, reviewers examined the conclusions regarding safety and coded them as unsafe, safe, unclear or mixed, or not discussed. Conclusions about effectiveness were coded as follows:

(1) ineffective; (2) effective; (3) neutral, mixed, or insufficient evidence; and (4) not discussed. Because the authors were interested in negative publications, articles were categorized for analysis as “unsafe” versus “other” and as “ineffective” versus “other.”

Data were entered into a Microsoft (MS) Access Database and transferred to MS EXCEL for descriptive analysis; Stata 8.1 software was used for statistical analysis.

The authors report that, on average, 30 issues were reviewed for each of the 11 primary journals (range, 12 to 52). The average number of pages per issue ranged from 56 to 217, and the average number of all advertising pages ranged from 3.9 to 87.8 per issue. The average number of pharmads varied from 0.15 to 66.3 pages per issue and from 0.001 to 0.441 pharmads per average number of journal pages per issue.

Two journals had fewer than 10 pharmad pages in an average issue and were labeled as the “fewest pharmads” group. The seven journals with between 10 and 39 pages per issue were named the “middle pharmads” group, and the two with more than 40 pages per issue, the “most pharmads” group.

The journals with the most pharmads published fewer major articles (0.08 per issue) about DS than the middle pharmads journals (0.21) (P<0.05); the middle pharmads journals published fewer major DS articles per issue (0.21) than those with the fewest pharmads (0.43), (P<0.05). The difference in major DS articles between journals with the most pharmads and fewest pharmads was most significant (P<0.01).

The DS written about most often in the medical journals were folate and other B vitamins, caffeinated beverages (it is questionable whether such beverages actually qualify as DS), calcium and vitamin D, iron, and essential fatty acids such as omega-3 fatty acids.

Safety concerns were raised less often in clinical trials or cohort studies than in other articles. Concerns about unsafe DS were cited in 1/44 (2%) clinical trials or cohort studies versus 3/34 (8.8%, though the article states 10%) of editorials or reviews and 20/177 (11%) of other types of articles. More journals with the most pharmads (67%) were significantly likely to publish major articles concluding that DS were unsafe than journals with middle (7%) or fewest (4%) pharmads (P<0.005).

In the 10 primary journals, 68 of 254 (26%) articles about DS concluded they were ineffective; only 10 of these articles were clinical trials or cohort studies. Conclusions about ineffective DS were less common in journals with fewest pharmads (27%) than in journals with more pharmads (34%); the differences were not significant.

In the three CAM journals, the number of total ads ranged from 5.7 to 24 pages per issue, with no ads for prescription pharmaceuticals found in those journals. The number of pages of DS ads ranged from 0 to 12.3, with an overall average of 5.5 per issue. Not surprisingly, the CAM journals had significantly more articles about DS than any group of the primary journals (P<0.01). The CAM journals published more than twice as many clinical trials or cohort studies as the general medical journals with the fewest pharmads (0.5 vs. 0.22 per issue); the number of major articles per issue was significantly higher among CAM journals (0.86) than among the regular journals with the fewest ads (0.43) (P<0.05). The authors report that although CAM journals published more original science about DS, the proportion of major articles concluding that DS were unsafe or ineffective was not significantly different from general journals with middle or fewest pharmads.

These results support the authors’ hypothesis that pharmaceutical advertising biases journals against publishing articles on DS and in publishing more articles that DS are unsafe. The results are consistent with substantial research suggesting that advertising influences behavior.

According to the authors, this study was limited by the fact that it included the American library version of only a few clinical medical journals. The secondary analysis of CAM journals could have been strengthened by a larger sample of more diverse CAM publications. In addition, this study did not survey journal editors about the number of submissions of different types of articles they receive or how they decide which ones to include. Also, according to the authors, this study used the number of issues per journal as the study denominator rather than the total number of articles per issue; future studies could use the number of articles per issue as the denominator to address the related question of whether journals with more advertising per issue also have fewer articles of all types and therefore fewer articles about DS.

An HerbalGram peer reviewer, who has extensive experience contributing to medical journals, has added that other potential confounders are that DS manufacturers might not be able to afford the cost of advertising in journals supported primarily by more lucrative pharmads. Further, they may have preferentially chosen to advertise in journals that are likely to be more receptive to the use of DS and perhaps provided more affordable advertising space as well, presuming that the audience of such journals are more open to the professional use of DS. Clearly, the reviewer writes, editors seem to preferentially publish about products (whether they be DS or pharma) that help support their publication and distribution costs.

—Shari Henson