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A new study, co-authored by a University of Arizona professor emeritus and published in The American Journal of Medicine, suggests that a whole-diet approach, which focuses on increased intake of fruits, vegetables, nuts and fish, is a better strategy for reducing cardiovascular risk than approaches that focus exclusively on reduced dietary fat.
The new study explains that while strictly low-fat diets have the ability to lower cholesterol, they are not as conclusive in reducing cardiac deaths. By analyzing major diet and heart disease studies conducted over the last several decades, investigators found that participants directed to adopt a whole-diet approach instead of limiting fat intake had a greater reduction in cardiovascular death and nonfatal heart attacks.
Early investigations of the relationship between food and heart disease linked high levels of serum cholesterol to increased intake of saturated fat and, subsequently, an increased rate of coronary heart disease. This led to the American Heart Association's recommendation to limit fat intake to less than 30 percent of daily calories, saturated fat to 10 pecrent, and cholesterol to less than 300 milligrams per day.
"Nearly all clinical trials in the 1960s, '70s and '80s compared usual diets to those characterized by low total fat, low saturated fat, low dietary cholesterol and increased polyunsaturated fats,” said study co-author Dr. James E. Dalen, executive director of the Weil Foundation and professor and dean emeritus of the UA College of Medicine. "These diets did reduce cholesterol levels. However, they did not reduce the incidence of myocardial infarction or coronary heart disease deaths."
Carefully analyzing studies and trials from 1957 to the present, investigators found that the whole-diet approach, and specifically Mediterranean-style diets, are effective in preventing heart disease, even though they may not lower total serum or LDL cholesterol.
The Mediterranean-style diet is low in animal products and saturated fat, and encourages intake of monounsaturated fats found in nuts and olive oil. In particular, the diet emphasizes consumption of vegetables, fruit, legumes, whole grains and fish.
"The potency of combining individual cardio-protective foods is substantial – and perhaps even stronger than many of the medications and procedures that have been the focus of modern cardiology," said study co-author Dr. Stephen Devries of the Gaples Institute for Integrative Cardiology in Deerfield, Ill., and the Division of Cardiology at Northwestern University. "Results from trials emphasizing dietary fat reduction were a disappointment, prompting subsequent studies incorporating a whole-diet approach with a more nuanced recommendation for fat intake."
Based on the data from several influential studies, which are reviewed in the article, Dalen and Devries concluded that emphasizing certain food groups, while encouraging people to decrease others, is more cardio-protective and overall better at preventing heart disease than a blanket low-fat diet. Encouraging the consumption of olive oil over butter and cream – while increasing the amount of vegetables, fruits, whole grains, nuts and fish – promises to be more effective.
"The last 50 years of epidemiology and clinical trials have established a clear link between diet, atherosclerosis, and cardiovascular events," Dalen said. "Nutritional interventions have proven that a 'whole-diet' approach with equal attention to what is consumed as well as what is excluded is more effective in preventing cardiovascular disease than low-fat, low-cholesterol diets."