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17 January 2019 -Scribd/The Nutrition Coalition - Dr. Walter Willett: Numerous Potential Conflicts of Interest

The Nutrition Coalition


Summary: Coalition of scientists claim that Walter Willett, leader of the EAT-Lancet section on diet and health, has "multiple serious potential conflicts of interest which cast doubt on his ability to bring an unbiased viewpoint to the question of whether a vegan/vegetarian diet is preferable for good health".


According to this report from the Nutrition Coalition (a US-based not-for-profit organisation who describe themselves as "an independent, science-based group that exists purely in the public interest, free from any industry agenda"), the lead author of the recent EAT-Lancet report  has not only a long history of advocating vegetarian and/or vegan diets, but also a wide range of potential commercial conflicts of interest relevant to this publication.

This report broadly advocates a 'plant-based' diet, basing this on claims that this is the most beneficial type of diet both for human health and to protect the environment, and has (understandably) attracted significant media coverage, e.g see:
And inevitably, not all of that coverage is uncritical....  see also:

Dr. Walter Willett: Numerous Potential Conflicts of Interest

Summary: Walter Willett, leader of the EAT-Lancet section on diet and health, has multiple serious potential conflicts of interest which cast doubt on his ability to bring an unbiased viewpoint to the question of whether a vegan/vegetarian diet is preferable for good health.

Principal findings:

  • Willett has advocated for a vegetarian diet, including little-to-no red meat consumption, since 1990/1991. In recent years, he has increasingly been leaning towards veganism.
  • Willett has published more than 200 papers on epidemiological data (which can show association but cannot demonstrate cause-and-effect) with findings that 1) red meat is bad for health, 2) that animal fats are bad for health, and/or 3) that a diet of grains/fruits/vegetables or vegetarianism generally is better for health. He has also published three commercial diet books that make these same arguments.
  • In the last few years of Willett’s directorship of the Harvard T.S. Chan School of Public Health, the school received between $455,000 and $1,500,000 from companies or groups interested in promoting vegetarian products or the vegetarian diet generally. The school also received between $350,000 and $950,000 from pharmaceutical companies, which presumably would not benefit from a nutritional solution to chronic disease.
  • Willett is an Advisor or Scientific Advisor to at least 7 groups/commercial enterprises that promote high-grain, vegetarian diets.
  • Willett has been closely involved in numerous commercial ventures with David Katz, a prominent promoter of the vegetarian diet who has received millions from food companies.
  • Willett rarely, if ever, discloses these potential conflicts of interest. Willett is the co-chair of the EAT-Lancet report, which does not disclose any of his potential conflicts of interest. Willett is the principal nutritionist on the EAT-Lancet report. The other nutritionists on the paper have published almost nothing on the subject of diet and disease, and nothing that contradicts Willet’s views.

Thus, on the subject of diet and health, the report presents only one viewpoint. This report cannot be considered a balanced paper

There are many scientists who do not believe that the plant-based diet is best for health. Indeed, the 2015 U.S. Dietary Guidelines Advisory Committee, which favored a vegetarian diet, nevertheless concluded in its report that the evidence for any disease-fighting powers of this diet was “limited” –  the lowest rank given for available data.

Potential ideological/intellectual conflicts of interest:

  • Willett has promoted vegetarian diets since at least 1990/1991.
  • "Moderate red meat intake is certainly better than large amounts, but it’s quite possible that no red meat intake is even better,” said Dr. Walter C. Willett (1990).
  • Doctors Walter Willett and Frank Sacks, researchers at the Harvard School of Public health… told us that vegetarianism is still the best way to go for anybody who is serious about lean.” (1991).
  • We suggest that Dr. Small and his colleagues enjoy an occasional meatball when the urge becomes irresistible, preferably with a glass of red zinfandel… Beyond our land of meat and potatoes, the world’s vast array of vegetarian dishes containing no cholesterol and little 16:0 and 14:0 fatty acids provides an eating adventure, between the occasional meatballs, that Americans are only beginning to explore.” Walter Willett, M.D., Dr.P.H. Harvard School of Public Health Boston, MA 02115 Frank M. Sacks, M.D. Harvard Medical School Boston, MA 02115 (Letter to the Editor, New England Journal of Medicine, Jan 10, 1991).
  • “Steak is no longer part of the Willett lexicon; he gave up red meat after the colon cancer study… The optimal diet, he says, is the Mediterranean menu - plenty of fruits and vegetables, very little meat or chicken.” (1993)
    • Note: the “colon cancer” study noted above concluded: “These prospective data provide evidence for the hypothesis that a diet high in saturated fat increases the risk of colorectal adenoma.” This is an epidemiological finding (which can show association but not prove causation) only on saturated fat/low fiber, but these are in no way synonymous with red meat. Also, the study was confined exclusively to male doctors and therefore could not be generalized to a larger population.
    • Dr. Walter Willett, chairman of the department of nutrition of Harvard’s School of Public Health, calls the book [A Teen’s Guide to Going Vegetarian] “a sound guide for teens in the dietary jungle of America.” (1994)
    • Willett said, “the optimum amount of red meat you eat should be zero”. (2001).
    • Willett said , “The less red meat, the better. At most, it should be eaten only occasionally. And it may be maximally effective not to eat red meat at all.” (2001).
    • Willett has been a featured speaker for conferences promoting vegetarian/vegan diets: The Third Annual Congress on Vegetarian Nutrition, 1999; The Ivy League Vegan Conference, 2017.

Since 1983, Willett has published hundreds of papers concluding that fruits/vegetables and plant fats/proteins are healthy while animal fats/proteins/red meat are unhealthy. All of these papers are based on epidemiological data, which is fundamentally weak and cannot demonstrate “cause and effect.” Willett’s papers include:

  • 78 findings that red meat is associated with a negative health outcome
  • 37 findings that animal fats are associated with a negative outcome or that polyunsaturated vegetables are associated with a positive outcome. (Willet’s writings are highly inconsistent on the question as to whether animal fats might be a possible reason for the negative health consequences he associates with red meat.)
  • 130 findings that vegetarian or mostly-vegetarian diets are associated with a positive health outcome.
  • Willett is also the author of three diet books that advocate a largely vegetarian diet for health, weight loss, and fertility.

Note: the quality of Willett’s evidence base is fundamentally weak.

Epidemiological studies are a weak form of data that are meant to generate hypothesis,  but not to prove them. They show associations and cannot, in the vast majority of cases,  be used to demonstrate cause and effect. Only clinical trials, which are a far more rigorous kind of evidence, can demonstrate cause and effect.

Epidemiological findings in nutrition, when tested in rigorous clinical trials, have only been found to be correct only 0-20% of the time. This means, 80-100% of the time, they are wrong.

Willett has never been able to confirm a biologically plausible mechanism by which red meat might cause ill health.

 He rejects the idea that saturated fats are a possible reason. Other proposed mechanisms, such as excessive heme iron or TMAO, have never been demonstrated in human clinical trials to cause heart disease. Meat does not contain glucose, which is the driver of both obesity and type 2 diabetes. Thus, there remains no proven mechanism by which red meat might cause disease.


It seems clear, from the above information, that Willett has, for nearly 30 years, had a strong intellectual bias in favor of the vegetarian/vegan diet.