Diet and Health

March 28, 2010

I should be clear about this: I am a fat man. I have more than my share of the diseases characteristic of the 21st century. I do not deny that my lifetime diet has played a huge part leading up to my present state of health. I am not the person you want to consult when it comes to diet and health. I accept a major share of the responsibility for my fate. To question the link between diet and health would be crazy.

But there is a place for crazed thinking in food ethics. With no implied application to my own personal case, the tendency to connect diet and health in contemporary food ethics is as overblown as it is irresistible. Michael Pollan’s work is a case in point. He started out focused on ecological and cultural themes, and wrote broadly on diet and ethics (often focused on animals) in The Omnivore’s Dilemma. As his celebrity has grown, he has been drawn, kicking and screaming at times, into America’s obsession with diet and health. His short book In Defense of Food provides a devastating critique of what he calls “nutritionism”: the tendency to reduce all food values to their constituent part so that they may be assessed through scientific studies of the diet/health relationship. In place of this, Pollan suggests some simple advice that has been advocated by one of my friends and heroes, Joan Dye Gussow, for many years: eat real food.

Gussow’s reasons for eating real food (that is whole rather than processed foods—Pollan summarizes this by advising us to shop around the edges of the grocery store) are as much cultural, historical and political as they are nutritional. And the reason for downplaying the health angle is that the study of diet/health relationships has been plagued by insurmountable obstacles. For any individual (that would be you and me) the cause of good health is going to be a very complex mix of difficult-to-sort out things. Good genes mean a lot. But among things under your control, physical activity may be the most decisive. The meals that an average farmer of the 1900s ate are hardly consistent with today’s food pyramid, but if you are in the fields all day busting your butt, you are not likely to become obese.

But you might get fat in spite of all that, or you might have a stroke at age 52, and that’s why it is, I repeat, crazy to deny a connection between diet and health. The scientific study of diet and health is necessarily a study of large populations, and these studies are only very weakly correlated to things like genetics and physical exercise. One can tease out broad relationships with some degree of certitude, and that is the thinking behind the food pyramid and other dietary advice. Some recent work has shown that what your grandparents ate may be having as much causal influence over your health as what you yourself ate! But moving from these statistical correlations to dietary advice that will get taken up by individuals is a minefield of fallacious inferences. For years it was thought that Japanese diets high in fish and low in fat contributed to low rates of heart disease, and this correlation still is the basis of nutritional advice. But now some analysts suggest that the whole thing may have just been a discrepancy in the way heart disease is reported in Japan.

Public health officials and nutritionists are also making very broad assumptions about what you are already eating and how you spend your day when they put together dietary recommendations.  These assumptions also reflect statistical averages. One possible fallacy here is that the person who is already mindful of what they eat is almost certainly quite far from “the average American” in what, when and how they eat. It is also that person who may be most likely to be looking for dietary advice. And if you are reading this blog, you are probably well on the way to becoming mindful. The official food pyramid has now become a set of guidelines that can be tailor to individuals according to a number of ethnic, genetic and lifestyle variables.

Given the American proclivity to link diet and health, it is not surprising that foodies have their own pet theories on the health giving attributes of kale or raw milk and the health robbing properties of meat and high fructose corn sweetener. To his credit, the svelte Pollan resisted the role of diet-health-advice-giver as long as he could but if you are thin and good-looking and the likes of Oprah Winfrey and Linda Wertheimer have asked you for rules, you finally give in. As for me, I’m holding out: no advice on diet and health. I’ll defend your ethical right to hold onto whatever crazy theory you have, but as for me, I’m keeping mum.

Paul B. Thompson is the W.K. Kellogg Professor of Agricultural, Food and Community Ethics at Michigan State University

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