John P.A. Ioannidis

John P.A. Ioannidis
Nutrition research is among the most contentious fields of science. Although the totality of an individual's diet has important effects on health, most nutrients and foods individually have ambiguously tiny (or nonexistent) effects.1 Substantial reliance on observational data for which causal inference is notoriously difficult also limits the clarifying ability of nutrition science. When the data are not clear, opinions and conflicts of interest both financial and nonfinancial may influence research articles, editorials, guidelines, and laws.2 Therefore, disclosure policies are an important safeguard to help identify potential bias. In this Viewpoint, we contend that current norms for disclosure in nutrition science are inadequate and propose that greater transparency is needed, including a broader definition of what constitutes disclosure-worthy information.

Financial conflicts of interest have received substantial attention in nutrition science, particularly conflicts of interest involving the food industry, and for good reason.3 Food represents a huge market so it is logical that the food industry will try to promote its products and influence the scientific literature and opinion making.4 Major distortion may sometimes ensue for both the gathering of evidence and its interpretation.3 A financial disclosure registry may be helpful in understanding how the scientific literature, public policy, and individual and population dietary preferences might be affected. At the same time, the puritanical view that accepting funding from the food industry ipso facto automatically biases the results is outdated.5

Industry sponsorship is not the only form of financial conflict of interest germane to nutrition science. Some indirect financial gains may also be important. Many nutrition scientists and experts write books about their opinions and diet preferences. Given the interest of the public in this topic, books about nutrition, diets, and weight loss often appear on best-selling lists, even though most offer little to no evidence to support their frequently bold claims. Financial conflicts of interest can also appear in unexpected places. For example, many not-for-profit nutrition initiatives require considerable donor money to stay solvent. Public visibility through the scientific literature and its reverberation through press releases, other media coverage, and social media magnification can be critical in this regard.

Another aspect involves nonfinancial conflicts of interest. Allegiance bias and preference for favorite theories are prevalent across science and can affect any field of study. It is almost unavoidable that a scientist eventually will form some opinion that goes beyond the data, and they should. Scientists are likely to defend their work, their own discoveries, and the theories that they proposed or espoused. Nutrition scientists are faced with an additional challenge. Every day they must make numerous choices about what to eat while not allowing those choices to affect their research. Most of them also have been exposed to various dietary norms from their family, culture, or religion. These norms can sometimes be intertwined with core values, absolutist metaphysical beliefs, or both. For instance, could an author who is strongly adherent to some religion conclude that a diet-related prescription of his or her religion is so unhealthy as not to be worthwhile?

Advocacy and activism have become larger aspects of the work done by many nutrition researchers, and also should be viewed as conflicts of interest that need to be disclosed. These endeavors often spring from some of the noblest intentions and can lead to invaluable contributions to society and public health in particular. However, advocacy and activism are also orthogonal to a key aspect of the scientific method, which is to not take sides preemptively or based on belief or partisanship. Examples of white-hat bias (bias that distorts scientific evidence in support of a perceived righteous end such as better human health) have been reported.6

Therefore, it is important for nutrition researchers to disclose their advocacy or activist work as well as their dietary preferences if any are relevant to what is presented and discussed in their articles. This is even more important for dietary preferences that are specific, circumscribed, and adhered to strongly. For example, readers should know if an author is strongly adherent to a vegan diet, the Atkins diet, a gluten-free diet, a high animal protein diet, specific brands of supplements, and so forth if these dietary choices are discussed in an article. The types of articles in which relevant disclosure should be expected include original research, reviews, and opinion pieces (such as editorials). Such disclosure should not be seen as an admission of lack of integrity. To the contrary, disclosure strengthens the perceived integrity of the author. Moreover, some disclosures may end up being advantageous depending on future research findings. For example, if at some point strict vegan diets are shown definitively to confer unmatched health benefits, an author who previously disclosed strong adherence to that diet may receive extra recognition and acclaim for his or her prescient wisdom.

Readers and users of nutrition articles would be the beneficiaries of disclosure of dietary preferences of authors. They would understand when an author was practicing the message communicated in the article. At the same time, readers who are more undecided and skeptical would be alerted that an author is a strong advocate of the message to the point of making committed life choices based on what that author advocates. Even if the specific author is a visionary and his or her positions are all correct, such disclosures would allow readers to interpret the presented views in proper context. Availability of these disclosures would allow readers to be either more skeptical or more inspired (depending on how they view the presented evidence and arguments).

Should similar disclosure norms apply for articles on nondietary lifestyle behaviors? Most nondietary lifestyle behaviors differ from diet in 1 or more aspects that are relevant to whether disclosure is needed or not. First, some lifestyle behaviors have substantially stronger (and concomitantly less contested) effects than consumption of most nutrients and foods. For example, smoking increases the risk of many cancers approximately 10- to 20-fold, but red meat intake may increase the risk of colorectal cancer 1.02-fold (or may have no effect), and intake of fruits or vegetables may decrease the risk of cancer 1.002-fold per serving (or may have no effect). Second, no other lifestyle behavior has the ubiquity of food consumption. Third, nutrition has widespread public interest so distortion of evidence (originating or echoed) in widely read books and popular media7 has the potential to cause greater public harm. Fourth, extreme and committed behavioral stances that originate from family, culture, or religion are more common with diet.

"smoking increases the risk of many cancers approximately 10- to 20-fold"
And what are these people smoking?

Top US academics discover fresh tobacco leaves can fight cancer
"The leaf and flower of the tobacco plant contain high amounts of the key flavor ingredient called cembranoids, which shows promise as an anti-cancer agent,"
Smoking Helps Protect Against Lung Cancer
Japan and Greece have the highest numbers of adult cigarette smokers in the world, but the lowest incidence of lung cancer. In direct contrast to this, America, Australia, Russia, and some South Pacific island groups have the lowest numbers of adult cigarette smokers in the world, but the highest incidence of lung cancer.
See also: A comprehensive review of the many health benefits of smoking Tobacco

There are a few other nonnutritional interventions for which cultural or religious value judgments may also be particularly strong such as involving mindfulness meditation, tai chi, or circumcision.8 Similar disclosure of personal choices and practices may need to be considered for these as well. Still, nutrition stands apart because of the much higher volume of articles published and the ubiquitous, daily decision making involved with dietary choices. Furthermore, several other interventions are occasionally hotly debated in research journals and public media (eg, mammography).9 However, they usually lack the constellation of features listed above that makes nutrition so special.

As a general rule, if an author's living example could be reasonably expected to influence how some readers perceive an article, disclosure should be encouraged. Authors who have strong beliefs and make highly committed choices for diet or other behaviors should not hesitate to disclose them. Doing so may help everyone understand who is promoting what and why.