Mediterranean-Style Diet Cuts Heart Risks Almost 30%
For the first time, a large, randomized clinical trial has found that a Mediter-ranean-style diet can sharply reduce the risk of heart attacks, strokes and deaths from heart disease. Previous observational-only studies have suggested a benefit from adopting a diet rich in olive oil, nuts, legumes, fish and produce, including wine in moderation, but low in red and processed meat, full-fat dairy and commercial baked goods. This new clinical trial, however, surprised experts with the degree of risk reduction—almost 30%—associated with the Mediterranean eating regimen. The re-sults were so compelling that the study was ended early, after about five years, because researchers concluded it would be unethical to withhold the findings.
“This was a nice demonstration that consuming a diet consistent with current guidelines, whether it is called a Mediter-ranean-style diet or heart-healthy diet, is efficacious,” says Alice H Lichtenstein, DSc, director of Tufts’ HNRCA Cardiovascular Nutrition Laboratory. “The two experimen-tal diets were equally effective, one high in olive oil and one high in nuts. However, this does not mean olive oil or nuts can be added to any diet and the same benefits will be realized. This was a test of a dietary pattern, the whole package.”
The results were particularly striking, experts noted, because the study was rigor-ously designed and investigators focused on meaningful endpoints—heart attacks, strokes and death from heart disease. Lead scientist Ramón Estruch, MD, PhD, of the University of Barcelona, and colleagues trav-eled the world seeking input on the design of their study, which was published online in the New England Journal of Medicine.
Although the trial focused particularly on increasing consumption of olive oil or nuts as part of an overall Mediterranean-style diet, Dr. Estruch said he thought the total dietary change was key to the results. But researchers did not anticipate such dra-matic benefits so quickly. He added, “This is actually really surprising to us.”
OLIVE OIL OR NUTS: Dr. Estruch and col-leagues enlisted 7,447 people, ages 55 to 80, who were initially free of cardiovascular disease but who had either type 2 diabetes or at least three cardiovascular risk factors, such as smoking, hypertension or obesity. Participants were randomly divided into three groups, two of which followed a Mediterranean-style diet (see box, page 1):
- Mediterranean-style diet with at least four tablespoons daily of extra-virgin olive oil substituted for other types of fats.
- Mediterranean-style diet with an ounce (about a quarter-cup, a generous handful) of nuts daily—half walnuts and one-quarter each almonds and hazel-nuts—substituted for other foods.
- A lower-fat diet, which proved difficult to stick to and was in any case above current average levels of fat in the US diet.
Wine drinkers in the two Mediter-ranean-style groups could go ahead and have wine in moderation with meals every day. They could eat eggs and even chocolate as long it was at least 51% cocoa. They didn’t overdo it, however, as overall average body weight did not change. And sodas, commercial bakery products such as pastries, and fat-based spreads were all discouraged.
Both Mediterra-nean groups ate fewer carbohydrates and more fat—the difference being that the fat was heart-healthy monounsatu-rated (as in olive oil) or polyunsaturated (as in walnuts). Adherence to the diets was measured using urine testing for a compound called hydroxytyrosol found in olives and blood tests for alpha-linolenic acid from walnuts.After an average 4.8 years, the Mediterranean groups were 28% less likely to suffer any of the cardiovascular endpoints than the control group; there was no significant difference between the olive oil and nuts groups. The greatest benefit was against stroke, with a 49% lower risk among the Mediterranean diet groups.