Soy was also considered as a miracle food. When Japanese people move to the West, for example, their rates of chronic diseases like diabetes and heart disease go up. Researchers naturally wondered whether missing dietary elements might be responsible. They realized that these immigrants largely gave up soy for other protein sources, so the researchers focused on isoflavonoids, a group of chemicals found mostly in soy and suspected of guarding against chronic disease, says Christopher Gardner, a nutrition scientist at the Stanford Prevention Research Center. Again, a logical assumption didn't pan out in larger studies.
But what if it's not a single chemical or food that traditionally protected the Japanese, says Gardner, but how all components of their diet interact? "Maybe it's not just the tofu but the tofu in the stir fry with the sesame oil," he says. "The frustrating thing in nutrition is that for the last couple of decades, so many studies have failed because we've isolated one nutrient at a time, when probably the benefit comes from the synergistic and additive effects of the whole diet taken together."
Having in a sense returned to the drawing board, researchers are increasingly looking at those conventional patterns of eating as models for healthful eating. Dietary patterns are most easily described by their ethnic origins. "Low-carb or low-fat diets are a man-made phenomenon," says Van Horn. "Instead, what we're talking about is the more cultural, traditional, historical eating pattern—like the Mediterranean diet."
That's the dietary tradition with the most evidence behind it; scientists have been studying Mediterranean eating patterns and their impact on health since after World War II, when diet was suspected to account for the remarkable health of people living on Crete. Since then, research has associated the Mediterranean way of eating with a host of health benefits, including protection against diabetes, cancer, and heart disease.
Of course, there's a high degree of variability among the dietary traditions that encompass the Mediterranean, says Judith Wylie-Rosett, head of behavioral and nutrition research at the Albert Einstein College of Medicine in New York. The same is true of Asian and Latin American diets. But pretty much any traditional diet is better than our current westernized diet, which is, by all accounts, a mess. "The public-health crisis we are facing is a direct result of the western diet: lots of refined, processed, and manufactured food, lots of red meat, lots of added fat and sugar, very little whole grains or fruits and vegetables," says Michael Pollan, whose latest book, In Defense of Food, lays out the case for a holistic approach to eating.
So some nutritionists are taking a stab at more precisely describing dietary patterns, using statistical analysis to measure what foods tend to cluster together in the diets of healthy (or not healthy) people. For example, a "prudent" eating pattern is characterized by higher intakes of fruit, vegetables, whole grains, legumes, and fish, says Teresa Fung, a nutritionist at Simmons College in Boston. That pattern has been shown to be associated with a lower risk of coronary heart disease, type 2 diabetes, and colorectal cancer, as well as lower body mass index.
The prudent diet has some key similarities with most of the ethnic eating patterns. "A better diet, however you define it, almost always includes more fruits and vegetables, less processed meat, more whole grains, fish, nuts, and low-fat dairy," says Katherine Tucker, a nutritional epidemiologist at Tufts University's Friedman School of Nutrition Science and Policy.