Eating one serving per day of nuts in place of red meat was linked to a 30% lower risk of CHD; substituting a serving of fish showed a 24% lower risk, poultry a 19% lower risk and low-fat dairy a 13% lower risk.
"The few previous studies of red meat and heart disease largely looked at increasing red meat intake while decreasing all other, or at least unspecified, foods. We used a different approach to understand how replacing one protein-rich food with another was associated with heart disease risk," said Adam Bernstein, a researcher in the Department of Nutrition at HSPH and lead author of the study.
The study appears August 16, 2010, in an advance online edition of Circulation.
Many previous studies have focused on either the nutrient composition of protein-rich foods (for example, the amount of saturated fat or iron) or dietary patterns (for example, Mediterranean style diet or Western-style diet) and how they relate to heart disease risk. This study looked at substituting one protein-rich food for another, which may be easier for individuals compared with substituting one nutrient or one dietary pattern for another, in order to reduce the risk of heart disease.
The researchers followed 84,136 women aged 30-55 years in the Brigham and Women's Hospital-based Nurses' Health Study over a period of 26 years. The participants had no known cancer, diabetes, stroke, angina or other cardiovascular disease. To assess diets, the participants filled out a questionnaire every four years about the types of food they ate and how often.
During that time the researchers documented 2,210 non-fatal heart attacks and 952 deaths from CHD. After adjusting for age, smoking and other known cardiovascular disease risk factors, the researchers found that higher intakes of processed (such as bacon and salami) and unprocessed (such as steak and pork) red meat and high-fat dairy were significantly associated with an elevated risk of CHD. Higher consumption of fish, poultry and low-fat dairy was significantly associated with a lower risk of CHD.
A number of factors may account for the link between red meat intake and higher risk of heart disease. For example, many previous studies had found an association between the form of iron in red meat and risk of CHD; saturated fat and cholesterol may also contribute to greater CHD risk. The high sodium content of processed meats may also lead to heart disease.
"Our findings show clearly that source of protein in our diet has an important impact on our health, and we can't consider red meat, chicken, fish, beans, and nuts to be interchangeable," said Walter Willett, chair of the Department of Nutrition at HSPH and senior author of the study. "This should not be surprising because when we eat red meat we get a large dose of saturated fat, cholesterol, and a form of iron that can override our control mechanisms. If instead we eat nuts as a protein source, for example, we get unsaturated fats that reduce our blood cholesterol, no cholesterol itself, and lots of fiber, minerals, and vitamins."
One of the strengths of the study compared with previous studies was the large number of participants, the long follow-up period and the updated dietary data every four years. Also, the researchers say the findings are likely to apply to men as well.
"Our research adds to the growing and convincing body of evidence that red meat intake should be minimized or excluded from the diet in order to maintain cardiovascular health," said Bernstein.
Other HSPH co-authors on the study include Qi Sun, Frank Hu, Meir Stampfer and JoAnn Manson.
Support for the study was provided by the National Institutes of Health. Qi Sun was supported by a post-doctoral fellowship from Unilever, Inc.
"Major Dietary Protein Sources and the Risk of Coronary Heart Disease in Women," Adam M. Bernstein, Qi Sun, Frank B. Hu, Meir J. Stampfer, JoAnn E. Manson, Walter Willett, Circulation, August 16, 2010
Source: Harvard University