Mediterranean diet is healthy for your heart: study

The first study of its kind, researchers systematically evaluated almost 200 studies investigating dietary patterns and their link to coronary heart disease (CHD) conducted between 1950 and 2007 in the United States, Europe and Asia.

The study concludes there are certain food groups or dietary patterns, that are beneficial, including vegetables, nuts, monounsaturated fatty acids, and overall 'healthy' dietary patterns such as the Mediterranean diet. In addition, the researchers conclude there is strong evidence which supports that certain dietary factors such as glycemic index/load of foods and trans fatty acids are harmful.

Their study, A Systematic Review of the Evidence Supporting a Causal Link Between Dietary Factors and Coronary Heart Disease, appears in the Monday, April 13 issue of the Archives of Internal Medicine.

"We hope our comprehensive review will clarify healthy and harmful foods as related to heart disease for the general public," said senior author Dr. Sonia Anand, professor of medicine at McMaster and the Heart and Stroke Foundation of Ontario and Michael G. DeGroote Chair in Population Health Research.

"Concluding there is strong evidence that certain dietary patterns, or food groups which are clearly beneficial or harmful, is an easy message for health professionals to send to the general public," said Dr. Anand.

Dr. Anand hopes the study will encourage health professionals and dieticians to present information to the public in a less factual and more people-friendly manner.

For their study, the McMaster researchers used a set of criteria linking cause and health outcomes. The lead author was Andrew Mente, PhD and a post-doctoral fellow funded by the Heart and Stroke Foundation.

He says: "The findings highlight the importance of improving overall diet quality to maintain good cardiovascular health. People need to be cautious and not become too preoccupied with a few individual nutrients or food items, while ignoring diet in its totality."

The study raises a note of caution because all the evidence isn't in yet about the current general consensus that a reduced consumption of saturated-fatty acids and a higher intake of fruits and vegetables, polyunsaturated fatty acids including plant omega-3 fatty acids and whole grains is beneficial.

"This is cause for concern," the article says, "because dietary advice to limit the intake of a certain nutrient (dietary fat) may result in increased consumption of another (carbohydrates) which can have adverse effects on CHD risk factors."

"Moreover, without large prospective studies in which multiple health outcomes are evaluated, recommendations to modify a dietary component may decrease the likelihood of one chronic disease (CHD) at the cost of increasing another (cancer)," the researchers said in their paper.

Dr. Anand said the paper has a message for the scientific community. "What we have demonstrated is that, for some food groups and nutrients, there has been relatively weak information. Even though one study may be positive, there may be three others that are negative or conflicting. We really need to look at the totality of the evidence in the field before promoting something to the public at large."