ROCHESTER, Minn. — If you are a doctor and devout person of faith, and if your religion says vegetarianism is the diet endorsed by the Bible, can you be expected to study the science of food and health without bias?
It's an emerging question for the communities waging battle over methodological weaknesses in the dietary sciences, one highlighted by a recent, widely reported Mayo Clinic clinician-authored paper on the association between diet and prostate cancer.
The publication, a Journal of the American Osteopathic Association study by the Mayo oncology and hematology fellow Dr. John Shin and four Mayo Clinic Scottsdale colleagues, reviewed 47 studies dating back 11 years. It rendered a timely, vegan-friendly conclusion that diets high in dairy products "may be associated" with increased prostate cancer risk, and diets high in plant-based foods "may be associated" with decreased prostate cancer risk. The study was reported in new outlets across the U.S., U.K. and Australia.
For those who heard the news and came away with new reasons to swear off animal foods, a valuable piece of context went missing, however. Shin, like thousands of other clinicians across the country, is Seventh-day Adventist. Sermon-hosting sites offer links to the physician's religious lectures and he serves as a speaker in the Adventist Medical Evangelical Network (AMEN), an independent organization with the goal of "uniting the church to restore Christ’s ministry of healing to the world, hastening His return."
Why should a nutrition researcher's faith tradition matter? Because an Adventist ministry of healing includes the promotion of a plant-based diet. In response to a recent Forum News Service question asking if Adventism seeks to move the public towards a plant-based diet in keeping with religious beliefs about the foods that promote health, Shin responded in the affirmative.
"Yes," he replied, "because the original diet given to man in the garden of Eden as described in the Bible was a plant-based diet, Seventh-day Adventists believe that this is the ideal diet for maintaining and restoring health." Shin added that the purpose of the AMEN organization is to inspire Christian medical professionals "to incorporate whole person care into their practices," and he disputed that its mission is to bring about dietary change.
Like much of the research that now informs the U.S. Dietary Guidelines, the 47 studies the Shin paper analyzes to impugn dairy are of a methodologically weak form of science known as nutritional epidemiology, so-called case-control and cohort studies that contain no information about cause and effect. The studies were of varying size and quality, moreover, and their findings were all over the place. Most showed no effect, protective or harmful, for any foods in relation to prostate cancer.
Given these results, how did the Mayo group come to their dairy-cautioning, plant-promoting conclusions? By citing the plentiful number of studies with no finding, alongside the equal number of studies showing plants were good and dairy was bad, all as part of the same trend. Shin says this step was justified because the vast majority of papers with findings, matched though by null findings, showed plants to be protective and dairy harmful, a "pattern" favoring his vegan-friendly findings on foods and cancer.
Earlier this year, however, a team of Canadian researchers conducting a more rigorous statistical method found dairy to be without effect as often as harmful in relation to prostate cancer. The diagnosed rates of prostate cancer within the US during the period studied, moreover, are widely recognized to be inaccurate thanks to the overdiagnosis of prostate-specific antigen (PSA) screenings. When it comes to diet and prostate cancer, in other words, the room for investigator bias to affect an outcome is high.
Visions from God
Adventist dietary beliefs derive from the writings of Ellen White, its mid-19th century co-founder and spiritual prophet.
"She would go into trances and receive what she called visions from God," says Ronald L. Numbers, a professor emeritus at the University of Wisconsin and expert on the history of Adventism. Numbers says White began to describe visions on diet and health, leading her to become a vegetarian "distinguishing between clean and unclean meat according to the Levitical laws."
Among the hundreds of passages concerning diet which are attributed to White are several that look decidedly vegan or vegetarian. These include "meat eating deranges the system, beclouds the intellect, and blunts the moral sensibilities," and, "people everywhere should be taught how to cook without milk and eggs, so far as possible," and, "grains, fruits, nuts, and vegetables constitute the diet chosen for us by our Creator." Numbers says Adventists have a diversity of views about the dietary positions of Ellen White.
But Adventist scholars have taken credit for over 100 years of moving food practices away from animal foods and toward plants. White's contemporaries were early cereal pioneers in Battle Creek, Mich., and their products were instrumental in diverting Americans from bacon and eggs towards carbohydrate-laden breakfasts of today, changes believed to have contributed to the skyrocketing global burden of Type 2 diabetes and secondary illnesses of heart disease, hypertension, Alzheimer's and some forms of cancer.
Contemporary Adventism has figured in over 300 health outcome studies of its communities, often conducted with NIH funding and in partnership with researchers from Harvard School of Public Health. Though studies of church-going populations have characteristics that limit their usefulness, this sustained appeal within the medical literature to the benefits of Adventist so-called lifestyle medicine is cited widely, including by the so-called "Blue Zones" longevity initiative adopted in cities like Albert Lea, Minn.
In perhaps the most direct position of influence on the direction of dietary policies today, Joan Sabate, an acknowledged Adventist and professor at the SDA-affiliated Loma Linda University School of Public Health, currently sits on the Dietary Guidelines Advisory Committee of the USDA.
Shin says "Adventists focus on health because we believe that when the body is healthy, the mind is better able to comprehend spiritual truths, thus enhancing one’s relationship with God." He adds that the teetoling, tobacco- and caffeine-avoiding faith also promotes exercise, adequate sleep and spending time with family. But while exercise, sleep, and family time is largely uncontested in medicine, a rigorous debate exits over the wisdom of the advice to avoid animal foods.
Should being Adventist while studying nutrition require a disclaimer?
“"The real issue for me is that Seventh-Day Adventists began their religion as a health religion, so they are compromised in making broad decisions about society's health"”
"The real issue for me is that Seventh-day Adventists began their religion as a health religion, so they are compromised in making broad decisions about society's health," says Belinda Fettke, an Australian who blogs on the subject of Adventism and health. "We should be asking them how best to do a vegetarian or vegan diet, because they understand it. But they shouldn't be telling the world that animal fats and protein are dangerous, which is what they do ... I don't think I've ever come across a religion that's so involved in a health message, and I think that's a concern."
Shin counters that all researchers approach their work with a bias, it's just that his is visible.
"My Seventh-day Adventist faith provides me with the predisposition to believe that plant-based foods are healthful, and therefore I have an interest in conducting research to show whether or not this is true," he says. "In this sense, my ability to maintain my objectivity in conducting diet-related research would be no more compromised than any other dietary researcher, the only difference being that my predispositions can be more readily traced to my religion."
He says he believes requiring a disclosure "would imply that someone of that faith is somehow less qualified or trustworthy to conduct the research in question. It would be a form of discrimination."
When asked if a devout Adventist could make a dietary recommendation contrary to the faith, the historian Ronald Numbers is skeptical. "That would be difficult," he says.
"If you even found that eating pork contributed to health, you would be in a bad quandary ... I assume that the nutritional studies that show Adventists live longer, healthier lives are reasonably accurate. But then of course, studies of Mormonism show they live longer lives. And they're not vegetarian."
So, should Adventists be asked disclose their faith when conducting nutrition studies?
"That is an incredibly interesting question," he says.
CORRECTION This story has been updated to address an error regarding the findings in Dr. Shin’s paper. The cohort studies as reported were essentially split, with the addition of two meta-analyses finding dairy foods modestly raised risk.