The truth on foods and fats
Walter Willett is trudging up a long hill in a hamlet outside of Rome, taking advantage of a trip to Italy to see how olive oil is pressed. A professor of epidemiology at the Harvard School of Public Health, he is passionate about oil or, more precisely, fats. Saturated fats, trans fats, healthy fats like olive oil, and the risk of becoming too fat have played major roles in Willett's research and his vision of how humans can live healthiest and longest.
Most Americans may have never heard of Walter Willett, but they probably have been affected by his research. Aided by a team of scientists at Harvard's Nurses' Health Study, the largest women's health project in the world, Willett has produced many of the major observational studies linking diet and lifestyle to health. "Before Walt came along, we thought nutrition was related to disease--somehow," says Harvard's Frank Speizer, who began the Nurses' Health Study in 1976. "But the actual relationships between nutritional factors and chronic disease--Walt Willett should be credited with putting those on the map."
The list is long: Willett and his team have shown that alcohol increases the risk of breast cancer; that animal fats can lead to heart attacks and aspirin can prevent them; that coffee reduces the chance of diabetes; that daily walking is critical to good health and a long life. Their studies have described how fiber, fish, folate, and fruit may prevent diabetes, coronary disease, cancer, and blindness; how luncheon meats may lead to diabetes and margarine to cardiovascular disease. They've uncovered the costs of obesity; the benefits of olive oil and peanut butter; the hazards of refined starches and TV; the power of vegetables, vitamins, whole grains, and more.
Connections. Willett and his group publish some 50 papers a year in top medical journals--an astonishing output. But these epidemiological studies all show associations and risks rather than specific cause and effect. For that, science relies on testing Willett's associations with randomized clinical trials.
Willett grew up on a Michigan farm, eating red meat and potatoes. Yet, he now advocates a traditional Mediterranean diet of fruits, vegetables, beans, whole grains, fish, and olive oil as a primary source of dietary fat. His bestselling 2001 nutrition book, Eat, Drink, and Be Healthy, supports this diet, while attacking the U.S. Department of Agriculture's food guide pyramid for its low-fat approach.
Willett has never been a scientist who shrinks from controversy. "He upsets a lot of people," says Margo Wootan, director of nutrition policy at the Center for Science in the Public Interest. "He thinks about the implications of his research and advocates changes." The best example: his fight over trans fats in prepared foods.
Small amounts of trans fats occur naturally in some foods. But most result from cooking or baking with liquid vegetable oils that have been "hydrogenated," or formed into solids by the addition of hydrogen (think margarine). Their long shelf life made these oils the fat of choice for food makers and fast-food chains.