October 3, 2008, 11:33 am

What’s the Healthiest Diet of All?

By Peter Libby, M.D.

Diners at an outdoor cafe in Corsica, France. (Ed Alcock for The New York Times)

What exactly do doctors mean by a “healthy diet”?

Many of us consider the Mediterranean diet to be the closest thing known to an ideal meal plan, rich in vegetables, fruits, legumes, cereals, fish, olive oil and, yes, a bit of red wine with meals. Compared to traditional American menu — high in red meat and in butter and other dairy products — the Mediterranean diet is lower in saturated fat, more varied and often more satisfying.

Decades worth of research also suggests that this way of eating is healthier. Many studies have documented reduced rates of heart disease and cancer among those adhering to a Mediterranean diet, compared to those eating more red meat and dairy-based regimens. Most of these studies have involved observations rather than actual intervention trials, however, and they have varied in size.

Now the British Medical Journal has published a systematic compilation of a dozen of the most methodologically sound of these observational studies, which included over 1.5 million people followed for up to eighteen years, analyzing cardiovascular consequences and some other important health outcomes. This large meta-analysis found decreased cardiovascular death as well as cancer mortality, as well as a lowered incidence of Parkinson’s disease and Alzheimer’s disease, in those following the Mediterranean diet versus those on other diets.

While such meta-analyses have limitations and cannot be considered as persuasive as large, randomized intervention trials, the new study further supports the idea that the Mediterranean diet can confer important health benefits.

Different diets abound, many even promoted by physicians. But it’s a mistake to think of a diet as a temporary measure; instead, it is a lifetime commitment to healthy choices. Need to lose weight now? Don’t rush. Take comfort in knowing that even a modest incremental reduction can confer significant health benefits, lowering your risk of heart disease or diabetes. Crash diets only set us up “yo-yo” weight loss and regain.

Whatever eating habits you adopt must be sustainable over the long term. Many researchers regard this as the Mediterranean diet’s greatest strength. You can stick to it, and like it, year after year.

How sad, then, to learn that a diet that whose adherents were among the longest-lived in the world is now fading from view. The governments of Greece, Italy, Spain and Morocco have asked that UNESCO designate the Mediterranean diet an “intangible piece of cultural heritage.” But as The Times recently reported, fast food is proliferating across the Mediterranean region, threatening to propagate a U.S.-style obesity epidemic.

In Greece, three-quarters of the adult population is now overweight or obese, and at increasing risk for diabetes, heart disease and arthritis, among other maladies. “Much of the highly praised diet didn’t exist any more,” said a senior economist at the United Nations. ”It has become just a notion.” Rather than turning our backs on this traditional diet, the new data suggest we could all derive substantial health benefits from it.

[For some dishes with a Mediterranean flair, check out The Times' Recipes for Health. -- Eds.]