Coronary heart disease (CHD) is less common in Mediterranean countries than in other industrialized nations. Previous studies have associated Mediterranean dietary practices with reduced mortality. Two components of the Mediterranean-style diet (olive oil and nuts) contain ingredients that may have beneficial effects on cardiovascular risk. Estruch and colleagues compared the short-term effects of two Mediterranean-style diets and a low-fat diet on cardiovascular risk markers.

The multicenter, randomized trial was a three-month subset of the four-year Prevención con Dieta Mediterránea (PREDIMED) study and involved 772 adults at high cardiovascular risk who had no symptoms or history of CHD. The investigators defined high risk as being a man between 55 and 80 years of age or a woman between 60 and 80 years of age with type 2 diabetes or three or more CHD risk factors (see accompanying table). Potential participants were excluded if they had a severe chronic illness, allergy or intolerance to olive oil or nuts, or were unlikely to change diets.

Eligible participants were randomly assigned to one of three diet groups: (1) low-fat diet; (2) Mediterranean diet with olive oil; (3) Mediterranean diet with nuts. Baseline health and demographic characteristics of all groups were similar. Each participant met with a dietitian who offered advice and meal plans based on the type of diet assigned. In addition, the Mediterranean diet groups met with the dietitian in a group session and received free servings of olive oil or nuts.

After three months, the Mediterranean diet groups had statistically significant greater improvements in systolic and diastolic blood pressures, fasting blood glucose and insulin levels, and high-density lipoprotein cholesterol levels compared with the low-fat diet group. The low-fat diet group experienced no change in average systolic blood pressure. Participants with preexisting hypertension who followed either Mediterranean diet demonstrated the largest blood pressure reductions.

The authors conclude that the two Mediterranean-style diets were more effective than a low-fat diet at improving cardiovascular risk markers after three months. They also conclude that the high-fat content of the Mediterranean-style diets did not lead to weight gain. It remains to be seen if the PREDIMED study, when completed, will link these short-term improvements in risk markers to long-term improvements in clinical outcomes.

editor’s note: The study by Estruch and colleagues adds to existing evidence that it is not enough for physicians to simply recommend a low-fat diet to reduce cardiovascular risk. Certain types of fats are likely to be better for the heart than others. A recent analysis of the Women’s Health Initiative dietary modification trial found no association between total fat intake and risk of cardiovascular events in postmenopausal women, but suggested that risk may be lowered by reducing intake of saturated andtrans fats.¹—k.w.l.