America clearly needs dietary guidance.
More than 44 million people are clinically obese compared with 30 million a decade ago, putting them at increased risk for heart disease, stroke, type 2 diabetes, and breast, prostate, and colon cancers. In the meantime, the noun diet seems to attract a different adjective every week, including Atkins, Ornish, Cooper, grapefruit, rice, protein, Scarsdale, South Beach, Beverly Hills, Best Chance, Eat Smart, and Miracle, not to mention Help, I’m Southern and I Can’t Stop Eating. While some of these plans overlap, others seem to specifically contradict each other, notably the meat-intensive regime of the late Robert Atkins versus the near-vegetarian program of Dean Ornish.
No wonder Americans are tempted to follow Mark Twain’s admonition to “eat what you like and let the food fight it out inside.” But still, we wonder: Is there really an optimum way to eat?
Although debate rages, academic nutrition researchers have begun to form a consensus around a plan with an important advantage—it is based on a preponderance of sound science. The regime does not as yet have a name, but it might well be called the Willett diet, after its leading proponent, Walter Willett, chairman of the department of nutrition at the Harvard School of Public Health.
Featuring abundant fruits, vegetables, whole grains, and vegetable oils, as well as optional portions of fish and chicken, Willett’s plan resembles the much-touted Mediterranean diet shown in several studies to reduce the risk of heart disease. Nonetheless, Willett resists the comparison. “The Mediterranean diet is specific to a certain climate and culture,” he says, adding that by focusing on healthy ingredients rather than specific dishes, “anyone can adapt this plan to his own tastes.” The results: stable blood-sugar levels, easier weight control, clearer arteries, and overall better health.
In this case it’s hard science, not just opinion. Willett’s plan is based on the largest long-term dietary survey ever undertaken: the 121,700-participant Nurses’ Health Study, begun in 1976 by Harvard Medical School professor Frank Speizer, with dietary assessments supervised by Willett since 1980. The study isn’t just big: Willett carefully crafted it so that he and others could extract specific recommendations about food intake. Participants even surrender blood and toenail samples so that Willett can track absorption of trace elements and other nutrients. If a participant reports a major illness, such as heart attack or cancer, “we write for permission to obtain medical records for further details,” says Willett. To ensure that the data include both sexes and two generations, Willett and several colleagues also launched the Health Professionals Follow-Up Study, which includes 52,000 men, and the Nurses’ Health Study II, a survey of 116,000 younger women.
In the past, nutritional scientists have largely relied on studies of animals, small groups of people, and/or petri-dish biochemistry that may not reflect the vagaries of human metabolism, although Willett uses such studies when he deems it appropriate. His access to a
unique quarter-million-person pool of humans who carefully track both their diets and their health lends added credibility to his research. “When you put animal, metabolic, and epidemiological studies together and they all point in the same direction, you can be pretty confident about your conclusions,” Willett says.
Adding a small bag of French fries (26 grams of carbohydrates) to your lunch is the equivalent of ingesting 6.5 teaspoons of refined sugar. The glycemic index is 67 (medium). The glycemic load is about 17 (medium). Potatoes put glucose into the bloodstream as fast as or faster than refined sugar. (To understand glycemic load and glycemic index, see “Good Carbs/Bad Carbs” on page 49.)
While soft-spoken and self-effacing in person, Willett isn’t shy about using this formidable database to take on the federal establishment. His Healthy Eating Pyramid differs radically from the Food Guide Pyramid pushed by the U.S. Department of Agriculture. “At best, the USDA pyramid offers wishy-washy, scientifically unfounded advice,” Willett argues in his book, Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating. At worst, he adds, “the misinformation contributes to overweight, poor health, and unnecessary early deaths.”
The numbers back him up. Men and women in Willett’s studies whose diets most closely paralleled the Healthy Eating Pyramid’s guidelines lowered their risk of major chronic disease by 20 percent and 11 percent respectively, according to an article published in the December 2002 issue of The American Journal of Clinical Nutrition. That compares with reduced risks of 11 percent and 3 percent for those whose diets most closely mirrored the USDA pyramid’s guidelines.
“Nutrition used to be like religion. Everyone said, ‘I have the truth, everyone else is wrong,’ and there wasn’t much data to refute that,” says Willett. “Now we’re starting to have a real scientific basis for understanding what you should eat.”