BOSTON — In the hallway of an aging brick laboratory next to the Harvard School of Public Health, there sits an unusual archive: a metal filing cabinet, unmarked and guarded by lock and key, stuffed with tiny Manila envelopes containing the toenail clippings of nearly 70,000 American nurses.
The clippings will give Harvard researchers clues about whether certain minerals, contained in food and deposited in nails, affect breast cancer. Collecting them was the clever idea of a man with a mission, a mild-mannered Harvard professor who is conducting the world's largest study of how the foods we consume contribute to the illnesses that consume us.
His name is Walter Willett, and his aim is to put scientific facts behind the old adage "you are what you eat."
That may sound simple enough. But in an era when one can hardly pick up a newspaper without being assaulted by so much contradictory dietary advice that none of it seems believable, when the President of the United States must break up fights between his Cabinet members over what kind of labels to put on food, experts agree that the scientific evidence linking diet to disease is surprisingly, shockingly, slim.
Within the hallowed halls of Harvard, Willett and his team of several dozen researchers are on a furious quest to fill in the gaps. Again and again, their massive examination of the dietary habits of 121,700 female nurses, launched 12 years ago, has debunked dietary myths. And few take more delight in bashing myths than Willett.
Thought you were doing yourself a favor by drinking decaffeinated coffee? The Nurses' Health Study has found that caffeine won't hurt your heart, but decaf might. Cutting out wine and beer? Willett says moderate alcohol consumption actually lowers the risk of heart attack. But women beware; alcohol also raises the risk of breast cancer.
Gave up red meat? Give yourself a gold star. Willett's research says red meat raises the risk of colon cancer--a finding that, one colleague of Willett recalls, brought the placid professor face to face with "a couple of big tall Texans who came strolling in" to discuss the impact those nasty little studies were having on their cattle ranching business.
Switched from butter to margarine? Demerits are in order. Willett and his group are about to report that margarine is associated with increased risk of heart disease--a finding that, Willett says with more than the slightest hint of glee, is certain to create a stir.
And remember those reports about Chinese women who eat a low-fat diet and rarely get breast cancer? Bunk, says Willett, much to the chagrin of scientists at the National Cancer Institute and elsewhere who continue to place faith in this hypothesis--and to spend money on studies to prove it. The nurses reveal no connection.
Such findings--and there are plenty more on the way--have angered food industry executives, altered government policy and often exasperated dietitians who are struggling through the maze of conflicting reports to formulate nutritional advice. They have also earned Willett a place as perhaps the most respected and provocative researcher in the field of nutritional epidemiology, the relationship between diet and disease.
It is a relatively new scientific arena, and one that Willett has played a major role in developing. In fact, he wrote the book on the topic--a 396-page tome, published in 1990 and titled, appropriately enough, "Nutritional Epidemiology."
"He is viewed as \o7 the\f7 leader in the field of nutritional epidemiology in this country or in the world," said Louise Brinton, who supervises research involving the effect of environment on cancer for the National Cancer Institute. "I never hear nutritional epidemiology being mentioned without reference being made to Walter Willett.
"Really, until these studies had been launched, we weren't sure which components of diet might either be helpful or hazardous. A lot of what we hear . . . is based not on science but on speculation."
That speculation, rather than science, is helping to shape beliefs about which foods are healthful and which are not annoys Willett endlessly. Even more distressing, he says, is that this speculation has worked its way into official nutrition advice, which Willett says is often based on guesswork extrapolated from data that is incomplete.
Take, for instance, the American Heart Assn.'s well-known recommendation that no more than 30% of calories come from fat. A nice round number, says Willett, "but it's not based on much." More specific information is needed, he says, about how different types of fat--saturated, polyunsaturated, mono-unsaturated--affect disease.