Do Supplements Contribute to Eating Disorders?

Eating Disorders and Dietary Supplements: A Review of the Science was published in May of 2023 in Nutrients and authored by Susan J. Hewlings. To fully assess the article, multiple components need to be considered, including the methodology of the article, the author, and the journal. 

The Article

“It has been suggested that the use of dietary supplements may lead to eating disorders, despite a lack of evidence to support this conjecture. Therefore, the purpose of this review is to examine the evidence-based risk factors for eating disorders and discuss why connecting dietary supplements to eating disorder etiology is not supported by the scientific literature and may interfere with treatment.”

The article is a literature review, not a systematic review or a meta-analysis. This is important to know because literature reviews have virtually no research methodology. They offer very little new knowledge to a body of evidence and, as a result, are infrequently published. The best ones examine relatively new and understudied topics and summarize all relevant literature, relevant theories, and points of exploration for future research. Again, those are the good ones.

However, literature reviews are easily contrived. It is easy not to include all relevant literature and only the literature that best supports an argument the author(s) wants to make. The colloquial term for this is cherry-picking.

The article claims to review the evidence-based risk factors for eating disorders, of which Hewlings claims that there is virtually no evidence linking supplements and eating disorders. However, Hewlings seems to be operating under a very restrictive and incomplete definition of eating disorders: only those behaviors that promote weight loss. She describes increased protein powder consumption in boys for weight gain and performance as not an eating disorder because it is unrelated to weight loss. The reality is that eating disorders manifest differently in adolescent boys, with muscularity-oriented disordered eating being one of the most common manifestations. 

In addition, Hewlings seems to imply that because there is no one study linking supplement use and eating disorders, there isn’t a link. But in this case, absence of evidence is not evidence of absence. This is an emerging line of research. Again, the best literature reviews consider all the literature, theories, and explanations, not merely those convenient for a specific argument.

The Author

Two important statements can be found at the very end of the article: the funding statement and conflicts of interest. The funding statement claims, 

“This research was funded by a restricted grant to Nutrasource from the Council for Responsible Nutrition.”

The Council for Responsible Nutrition is a trade association and lobbying group for companies that manufacture dietary supplements. 

Hewlings is the sole author of this article, which is strange as the vast majority of peer-reviewed articles are a team effort. But it makes digging into her institutional affiliation much easier. In the article, she states that her affiliation is Nutrasource Pharmaceutical and Nutraceutical Services, Inc. The name itself should reveal what type of company they are  (ACSH published an explainer on nutraceuticals in 2021).

The company’s main landing page has a section called “How We Can Help.” Six offerings are listed under that heading, the first four of which are pet food and supplements, dietary supplements and natural health products, vitamins and minerals, and probiotics. Hewlings worked for a supplement company. 

The conflict of interest statement says,

“The author declares no conflict of interest. The funders had no role in the writing of the manuscript or in the decision to publish the manuscript.”

I find it relevant that the author, at the time of publication, worked for a company that manufactures dietary supplements. I also think it’s pertinent that the time she took to write the article was paid for by a grant from a supplement lobbyist group bestowed upon her employer, a supplement company. 

You may now ask, “Why would the journal publish this?”

The Journal

Nutrients is an open-access, peer-reviewed journal indexed in PubMed, Medline, and other databases. Open access means anyone can read the journal's articles, regardless of subscription. Typically, being indexed in Medline and PubMed is a measure of the journal’s caliber or acceptance. However, by itself, that is not a sufficient marker of journal quality.

Nutrients is owned and operated by the Multidisciplinary Digital Publishing Institute (MDPI). In 2014, they were included in the notorious Beall’s list of predatory journals. In 2018, the editors of Nutrients resigned due to pressure to publish “mediocre” manuscripts. According to the Physicians Committee for Responsible Medicine, 

“Between 2009 and 2017, Nutrients published just over 5,000 papers. By 2022, Nutrients published more than 5,400 articles in one year. Meanwhile, the time from manuscript submission to first decision sank to an all-time low—just 13.7 days.”

Additionally, in June of 2023 (note: one month after the publication of this article), the Physicians Committee for Responsible Medicine published another article laying out specific concerns including, but not limited to:

• The pay-to-publish framework overlooks scientific quality.
• The journal’s response to ethical complaints. 

Conclusion

After reviewing the methodology, or lack thereof, the author and the journal, I think it’s safe to say that relying on this article as evidence that supplements do not contribute to eating disorders is extremely misguided at best and calculated at worst. The jury is still out on this topic, and further research is needed, but there are reasons to suspect that some supplements may contribute to eating disorders. Claiming that we know either way is dishonest about the science, especially when the author and those promoting the article profit from loudly proclaiming that there is no link.