Tasteful Alternatives to the Heart-Healthy Diet

Désirée Lie, MD, MSEd

Disclosures

December 29, 2008

Commentary

A Palatable Alternative for a Heart-Healthy Diet

Until recently, the recommendations for a heart-healthy diet were strict and adherence was low. The food pyramid[1] from the United States Department of Agriculture (USDA), for example, is often used as a primary resource for dietary advice, but its specific recommendations on portion sizes may be hard to follow. Compliance has been reported as low for diets previously recommended for cardiovascular protection by the American Heart Association (AHA), the National Cholesterol Education Program, and the Seventh Report of the Joint National Committee on the Prevention, Detection, Evaluation, and Treatment of High Blood Pressure.[2,3,4]

The older AHA step 1 diets, for example, advised an intake of < 30% of calories from fat, 8% to 10% from saturated fat, and < 300 mg/day of dietary cholesterol for step 1 and < 30% of calories from fat, < 7% of calories from saturated fat, and < 200 mg/day of cholesterol for step 2.[2] Strict adherence to these diet regimens often required close monitoring and guidance. Referral to a dietician was (and still is) appropriate in patients who require secondary prevention, for example, after a myocardial infarction or with comorbidities of diabetes and hypertension.

For patients now seeking primary preventive strategies to address cardiovascular risk, a recent surge in the medical and nutritional literature supports alternative dietary approaches that include high-carbohydrate, low-fat; high-fat, low-carbohydrate-high-protein diets; and the Mediterranean diet. These diets have been examined and compared with the AHA step and 1 and step 2 guidelines for their impact on cardiovascular events and all-cause mortality for primary prevention and secondary prevention.

Studies on the Mediterranean diet have been especially positive.[5,6,7,8,9] Although most studies tend to be observational or retrospective population-based studies using recall as a measure of adherence, a randomized clinical trial comparing different dietary regimens suggested that the Mediterranean diet reduced individual cardiovascular risk factors.[10]

Key components of the Mediterranean diet[5,11,12,13] are a high intake of vegetable and fruit, fish as protein, use of olive oil (that retains the lipophilic components of the olive fruit and phenolic compounds with antioxidant and anti-inflammatory properties), tree nuts, legumes, moderate wine intake, and a low intake of animal fats and dairy products. Proposed mechanisms for the protective effects of a Mediterranean diet include a beneficial effect on lipoprotein metabolism, including lowering LDL-c, as well as improved vascular endothelial function and anti-inflammatory effects.[14,15] The protective effects may be the result, in part, of a reliance on plant rather than animal sources of fat. In addition, when used for weight loss, the Mediterranean diet performs as well as the low-carbohydrate and the low-fat diet.[13]

The PREDIMED study,[12,13,14] is a long-term, multicenter, prospective ongoing clinical trial involving 900 participants that is examining the impact of the Mediterranean diet on multiple outcomes using 3 interventions: a diet with virgin olive oil, one with mixed nuts, and a low-fat diet. Two recent reports from the PREDIMED study have demonstrated that a 12-month behavioral intervention for individuals and groups favorably modified food patterns[12] and that frequent intake of low-fat dairy products reduced systolic blood pressure[13] among patients with hypertension.

The 2006 AHA recommendations now come closer to the Mediterranean diet and advise a diet rich in vegetables and fruits, whole grains, and high-fiber foods. They suggest consuming fish, especially oily fish, at least twice a week and limiting intake of saturated fat to < 7% of energy, trans fat to < 1% of energy, and cholesterol to < 300 mg/day by choosing lean meats and vegetable alternatives, fat-free (skim) or low-fat (1% fat) dairy products, and minimizing intake of partially hydrogenated fats.[16]

Studies on the benefits of the Mediterranean diet may even extend beyond cardiovascular protection to include protection against new-onset diabetes,[15,17] hypertension,[18] metabolic syndrome,[19] and Alzheimer's disease.[20,21]

It is reasonable to expect a clinician to be current and up-to-date regarding the general recommendations for a healthy diet, including recommended serving sizes for the main components and foods to avoid. The Mediterranean diet has the advantage of being relatively easy to understand, highly palatable, permissive in allowing food groups that are appealing to a wide variety of patients with different ethnic and cultural backgrounds, and adaptable to different cooking styles.

What types of nuts provide the greatest health benefits?

Nuts are one of the key components of the Mediterranean diet. The second international nuts and health symposium was held in 2007 and was attended by scientists and nut industry representatives.[22] The first symposium had been held 12 years previously in 1995, so this meeting reflected the recent upsurge in interest in the benefits of nut consumption. Nut consumption is higher in the United States than in Europe, with one third of Americans reporting consumption an a given day compared with 7% of Europeans; peanuts are eaten most frequently compared with other nuts.[22] The US Food and Drug Administration in 2003 approved 2 qualified health claims for the relationship between the consumption of nuts and reduced risk for coronary heart disease. One was for nuts in general,[23] which included almonds, hazelnuts, peanuts, pecans, pistachio nuts, walnuts, and some pine nuts. The other qualified claim was for walnuts[24] at a dose of 1.5 oz (42 g) per day as part of a diet low in saturated fat and cholesterol. Since then, more evidence has emerged on the beneficial role of nuts in cardiovascular protection.[24,25,26,27] More recently, pistachio nuts have been demonstrated to have a favorable impact on lipoproteins over a 4-week period[28] and to promote cardiovascular health and metabolic factors.[29,30,31] Similar data are available for almonds[32,33] and for walnuts.[34] Many of these studies are supported by the nut industry. Of note, a December 2008 report from PREDIMED found that after one year, the prevalence of metabolic syndrome decreased 13.7% among those assigned to the Mediterranean diet plus mixed nuts, 6.7% among those assigned to the Mediterranean diet plus virgin olive oil, and 2.0% among those adhering to a traditional low-fat diet.[35] There are no head-to-head comparisons of different types of nuts, and long-term studies of cardiovascular outcome are lacking. More data are needed to determine the mechanism of the benefits, the role of nuts on the gut flora and endocrine functions, and the effect of processing on those benefits,[22] as well as to substantiate the long-term benefits of nuts. The current evidence does not appear to support intake of one particular nut over another for cardiovascular benefits. It should be noted that nuts are high in calories, and if eaten in excess, could offset their benefits.

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