In the wild, animals instinctively find and consume the foods best adapted to their bodies. Not so for humans. Agribusinesses, fast-food chains, and calorie merchants assail the consumer with edible products designed to maximize revenue, not health. The result is a plague of nutrition-related illness: obesity, diabetes, heart disease, cancer. And contradictory nutritional guidance from popular books and scientific researchers only intensifies our confusion about what to eat.
"It troubles me that the public is not getting the best available information," says Walter C. Willett, M.D., D.P.H. '80, professor of medicine and Stare professor of epidemiology and nutrition in the faculty of public health. For example, he says the U.S. Department of Agriculture (USDA) Food Guide Pyramid, ubiquitous on cereal boxes since 1992, is one major source of false intelligence. Since the department's mission is to promote American agriculture, not public health, Willett asks if it is "the best agency to be giving dietary advice. They have so many conflicts of interest."
Drawing on his own research and that of many others, Willett's new book, Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating, aims to provide unbiased dietary guidance based on state-of-the-art nutritional science. The base of its "Healthy Eating Pyramid" is daily exercise and weight control, two items overlooked in the USDA version.
The book also takes issue with specific USDA food guidelines. The USDA gives a global warning against fats and oils ("use sparingly"), but Willett says the problem isn't fats, but saturated fats and trans fats, like the partially hydrogenated vegetable oils found in many margarines and baked goods. Surprisingly, he makes plant oils, along with whole grains, the foundation of a healthy diet. He suggests nuts as "a great source of protein and other nutritional goodies," noting that their fats are mostly unsaturated. And he dissents from the National Dairy Council's white-mustachioed "Got Milk?" ad campaign, which urges drinking three glasses of milk daily to combat the nation's "calcium emergency." "[T]here isn't a calcium emergency," Willett writes, noting that the United States is near the top of the list in per capita calcium consumption, and that calcium supplements may in any case be a cheaper and healthier source because milk adds extra calories, saturated fat, and sugar to the diet.
Cereal makers love the USDA pyramid, which recommends a whopping 6 to 11 daily servings of bread, cereal, rice, and pasta. Willett again demurs and insists on a distinction: grains per se are not necessarily healthy. The key, he says, is to eat whole, as opposed to refined, grains, because even the much-touted "complex carbohydrates" include, for example, white rice or bread and pasta made with white, rather than whole-wheat, flour. These starchy foods have a high "glycemic index"--they rapidly raise blood glucose levels and trigger the copious secretion of insulin. "Refined starches stress the pancreas," Willett explains. Furthermore, over time, a diet heavy in refined starches and sugars can produce insulin resistance and adult-onset diabetes. "Insulin resistance is the key to a lot of what's going on," says Willett. "It is at the very center of the problems with our Western diet and lifestyle."
Willett looks with favor on the "Mediterranean diet," which relies on fresh fruits and vegetables, whole grains, and monounsaturated fats like olive oil and includes only small amounts of red meat and dairy products. That is an example of healthy peasant fare. "It used to be that lower socioeconomic status [SES] groups were leaner--there were a lot of 'fat cats' at the top of the pile," he says. "Upper SES groups gravitated to animal fats and highly refined foods, which entail greater risk of chronic disease. In recent decades, though, a lot of those SES gradients have reversed. Fish was once the poor person's food; now it's the premium upper-class food--poor people can't afford it. A gap has opened between lower-class and upper-class mortality; between 1960 and 1986, total mortality rates among American men decreased 50 percent--but were unchanged among lower SES groups. Most of the difference comes from access to sound health knowledge, and it's the best evidence that good information can have a major impact."~Craig Lambert
