Tuesday, August 9, 2011

'Diets' That Promote Health (and Always Have)

Earlier this year, the "Mediterranean diet" turned 15. Of course, for the people who actually live in the Mediterranean region, that's an absurd notion. They have been eating meals of fish, vegetables, and whole grains drizzled with olive oil, then washing it all down with a glass or two of wine for generations. What actually turned 15 is the Mediterranean Diet Pyramid, an attempt by nutrition experts to promote an alternative to the typical overprocessed, fat- and sugar-laden American diet.
Click here to find out more!

That pyramid—like other recently devised dietary guides built on age-old traditions—represents a way of looking at nutrition that's gathering steam these days. Rather than reducing a diet to its essential foods and then foods to their essential nutrients—vitamins, minerals, and other chemicals—and trying to isolate those that may contribute to good health, researchers are increasingly taking a step back and correlating health with broader eating patterns. "What we're talking about is the background diet," says Linda Van Horn, acting chair of preventive medicine at Northwestern University's Feinberg School of Medicine. "It's not the occasional hot fudge sundae or brownie; rather, it's the day-to-day, meal-to-meal, bite-to-bite: What is it that appears in your mouth?"

The focus is on finding the overall combination of foods that are associated with better health, without necessarily pinpointing individual elements of the diet that are responsible. That may involve studying how people in different areas of the world eat or, here at home, using statistics to study which foods the healthiest among us consume. "You find out who's healthy, then ask what they're eating and how much they exercise," says K. Dun Gifford, founder and president of Oldways Preservation Trust, the Boston-based food issues think tank that developed the Mediterranean Diet Pyramid. (More later on the exercise element, which often gets lost when people try to adopt a healthier diet.)

Oldways, which gets funding from food companies and trade associations, among others, and developed its recommendations in conjunction with the Harvard School of Public Health, has also created food pyramids for a traditional healthful Asian diet, which emphasizes vegetables such as bok choy and chilies, noodles, and beans, as well as a traditional Latin American diet. The group has also cooked up a healthful vegetarian pyramid; plant-based diets, when they include all the essential nutrients, are associated with low rates of chronic diseases and longevity.

A new paradigm. It's important to recognize the flaws in the old-fashioned approach to nutrition science, which is to search for the precise health-promoting vitamin or chemical in a food and then to isolate it. That often results in taking wonder ingredient X out of the food entirely and putting it into a pill or into foods it was never meant to be in (think orange juice spiked with the omega-3 fatty acids naturally found in fish). That kind of ingredient isolation and supplementation was appropriate when many people suffered from diseases caused by a lack of a certain nutrient, like scurvy (vitamin C) or rickets (vitamin D). Those problems could easily be fixed by adding back the missing piece. "But there's a big difference between deficiency diseases and chronic diseases, where it's more likely that there are multiple factors acting in concert," says Marion Nestle, a nutritionist at New York University and author of, most recently, What to Eat. "It's hard, in that situation, to tease out the role of a single nutrient."

Not that people haven't tried. Consider the health claims for various vitamins, minerals, and other nutrients over the years. Vitamins A and C, which are antioxidants, and carotenoids like beta carotene and lycopene were once touted as tools to fight chronic diseases like cancer. It was a logical hypothesis; people who eat a lot of fruits and veggies are healthier than those who don't. Shouldn't the chemicals that are unique to these foods be responsible? As it turns out, no. "The history has been that the first studies [to test individual nutrients] show fabulous benefits, and then as they were repeated with larger populations, better placebos, and better controls, not only were they not helping, but in some cases they may hurt," says Nestle. The poster child is beta carotene, which not only didn't stave off lung cancer but actually appeared to increase rates of the disease among smokers. (A similar outcome was reported earlier this year with vitamin E.) Now we're back to where we started: Fruits and veggies appear to be protective, but we still don't know why.

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.

The beauty of the pattern approach is that it's not necessary to know exactly what mechanism is leading to better health. "It could be one thing or multiple things," says Fung. For example, research recently suggested that the higher amounts of choline, an essential nutrient in the vitamin B family, and another nutrient called betaine—both of which are abundant in a Mediterranean diet—reduce inflammation, which may contribute to a host of diseases, says Steven Zeisel, director of the Nutrition Research Institute at Kannapolis, a branch of the UNC Chapel Hill School of Public Health. "But the truth is, I'd be foolish to rush out and eat those nutrients. I can eat closer to that pattern—less red meat, more olive oil—and not worry about which is the active ingredient," he says. In fact, it's not even clear that these patterns are healthier because of what's in them—it may be what's absent. "As soon as you eat the Mediterranean diet, you're eating less steak," says Gardner. "Maybe it had nothing to do with that. What we know is that if you eat that way, you're healthier."

So, is it that easy: We all just have to eat like the Greeks (or the Vietnamese, or the ancient Maya)? Well, yes and no. First, most of the evidence comes from observation, not rigorous scientific trials, so it doesn't prove cause and effect. But there's enough observational data to convince most researchers, and there is some experimental evidence: Trials showed that eating a low-sodium diet based on whole grains, poultry, fish, and nuts and lighter on the red meat, fats, and sweets lowered blood pressure.

A second caveat is that these ancient dietary patterns were long paired with a way of life that doesn't much exist in America—and it included a lot of exercise, says Pollan. Men in postwar Crete didn't laze around dunking bread in olive oil all day; they chased goats up hills. Even now, people in the Mediterranean and other parts of the world are more active, whether through vocation or because there's so much more walking as part of daily life. That's why the traditional food pyramids from Oldways all include exercise. (The government recommends 30 minutes a day of moderate exercise for heart health and 60 to 90 minutes a day for weight loss.)

And if you're watching your weight—and who isn't?—calories really do count. The key is replacing less healthful foods with healthier ones, not just adding tofu to your bologna sandwich or nuts to your sundae. As Pollan says, "Eat food. Not too much. Mostly plants." That doesn't mean eschewing all indulgences, but it does mean keeping an eye on day-to-day intake. "It's about the pattern over the long term," says Oldways' Gifford. "Do you think people in the Mediterranean get drunk after church on Sunday? Sure, they do! We're human, and you have to take the pressure off the pressure cooker."

Even with occasional excesses, adopting a sound dietary pattern may be both simpler and more wholesome than chasing down the latest superfood or nutritional supplement. "Finally, the field has come around to realize that it won't be a single nutrient," says Tucker. "We're back to old-fashioned advice: Eat a variety of good-quality whole foods. That's the way to stay optimally healthy."

By Katherine Hobson