Counsel patients at high risk for cardiovascular disease and stroke to follow a Mediterranean diet, which is associated with a 30% risk reduction.1
STRENGTH OF RECOMMENDATION
B: Based on one well-designed randomized controlled trial.1
A 62-year-old patient with diabetes, obesity, and a family history of early-onset coronary artery disease is motivated to make significant lifestyle changes. You recommend moderate aerobic exercise (30 min five d/wk) but wonder whether a low-fat or a Mediterranean diet would be more effective in reducing her risk.
Cardiovascular disease (CVD), including heart disease and stroke, is the leading cause of mortality in the United States. CVD accounts for one in every three deaths,2 and stroke is a leading cause of long-term disability.2 The direct cost of treating CVD is estimated at $312.6 billion annually.2
Many modifiable risk factors contribute to CVD, including smoking, sedentary lifestyle, obesity, alcohol consumption, and poorly controlled chronic disease, as well as an unhealthy diet. A recent report from the American Heart Association suggests that 13% of deaths from CVD can be attributed to poor diet.2
Focus counseling on at-risk patients
Primary care providers (PCPs) often struggle to effectively counsel patients on behavioral change strategies, facing many barriers. Chief among them are the lack of time, training, and confidence in their counseling techniques, as well as a lack of patient motivation and readiness to change.3 In recognition of these barriers, the US Preventive Services Task Force recently recommended that PCPs focus behavioral counseling efforts on patients at high risk for heart disease.4
Large observational studies have found an association between trans fat and increased risk for CVD, as well as decreased risk for CVD in patients adhering to a Mediterranean diet.5-11 This type of diet typically includes a high intake of olive oil, fruit, nuts, vegetables, and cereals; moderate intake of fish and poultry; and low intake of dairy products, red meat, processed meats, and sweets. It also includes wine in moderation, consumed with meals.
Data on the physiologic properties of olive oil, including its antioxidant, vasodilating, and antiplatelet effects—as well as its effects on LDL cholesterol that may inhibit atherogenesis—support the link between a Mediterranean diet and a decreased risk for CVD found in the observational studies.12,13 Until recently, however, no randomized controlled trial (RCT) had compared the effect of a Mediterranean diet with that of a low-fat diet for primary prevention of CVD.
Mediterranean diet significantly lowers risk
Prevencion con Dieta Mediterranea (PREDIMED) was a large RCT (N = 7,447) comparing two variations of a Mediterranean diet with a low-fat diet for primary prevention of CVD. This Spanish study enrolled men ages 55 to 80 and women ages 60 to 80 who were at high risk for CVD. The risk was based on either a diagnosis of type 2 diabetes or the presence of ≥ 3 major risk factors, including smoking, hypertension, elevated LDL cholesterol, low HDL cholesterol, overweight or obesity, and a family history of early heart disease.
Participants were randomly assigned to one of three dietary groups: One group followed a Mediterranean diet supplemented with ≥ 4 Tb of extra virgin olive oil per day; a second group was put on a Mediterranean diet supplemented by 30 g (about 1/3 cup) of mixed nuts daily; a third group (the controls) was advised to follow a low-fat diet. The majority of baseline characteristics and medications taken throughout the study were similar among all three groups.
Those in both Mediterranean diet groups were followed for a median of 4.8 years, during which they received quarterly dietary classes and individual and group counseling. The controls received baseline training, plus a leaflet about low-fat diets annually. In year 3, however, the researchers began giving the control group the same level of counseling as those in the Mediterranean diet groups to avoid confounding results.
Adherence to the diets was determined by a self-reported 14-item dietary screening questionnaire, plus urinary hydroxytyrosol and serum alpha-linoleic acid levels to assess for olive oil and mixed nut compliance. Self-reporting5 and biometric data indicated good compliance with the Mediterranean diets, and there was no difference found in levels of exercise among the groups.
After five years, those in the Mediterranean diet groups had consumed significantly more olive oil, nuts, vegetables, fruits, wine, legumes, seafood, and sofrito sauce (a popular tomato-based sauce) than the control group. Participants in the low-fat diet group had decreased their fat intake by 2%, while those in the Mediterranean groups had increased fat intake (by 2.03% for the olive oil group and 2.1% for the nut group). Overall, 37% of energy intake by those in the low-fat diet group came from fat (exceeding the < 30% of calories derived from fat intake that defines a low-fat diet), compared with 39% fat intake for those in both Mediterranean diet groups.