The types of food eaten in an effort to cut down on saturated fat may make a difference in reducing heart disease risk, according to a study of people with either high blood pressure or prehypertension. The study was supported by the National Heart, Lung, and Blood Institute (NHLBI), a part of the National Institutes of Health.
Investigators evaluated three diets that follow the principles of NHLBIs DASH (Dietary Approaches to Stop Hypertension) eating plan with some modifications. One diet emphasized carbohydrates, another diet emphasized protein, and the third emphasized monounsaturated fat. They reported that while all three diets lowered blood pressure, improved cholesterol levels, and reduced ten-year risk of heart disease by as much as 16 to 21 percent, two of these modified diets were even more effective in reducing some risk factors and estimated risk for heart disease than the diet richer in carbohydrates.
The Optimal Macronutrient Intake Trial to Prevent Heart Disease (OmniHeart) study will be presented today in Dallas at the American Heart Association annual conference, and also published in the November 15 issue of the Journal of the American Medical Association.
The diet with more unsaturated fat, primarily monounsaturated fat:
By providing all daily meals to 164 men and women for 41 days for each diet, researchers evaluated the three diets to determine whether replacing calories from saturated fat with calories from protein or unsaturated fat was better than replacing those calories with carbohydrate. Saturated fat is known to raise blood cholesterol, and public health officials recommend that it make up less than 10 percent of daily calories for healthy individuals and less than 7 percent of daily calories for individuals with heart disease risk factors.
Participants were age 30 or older and had either high blood pressure or prehypertension at the time of enrollment.
"These new findings open the door to further research on the diets long-term effects and the ability of people to follow these diets," said Eva Obarzanek, Ph.D., NHLBI research nutritionist and study co-author.
The OmniHeart study diets differed from each other in several ways:
"Our results emphasize the impact that diet can have on blood pressure and cholesterol levels, two of the major heart disease risk factors," said Lawrence Appel, M.D., M.P.H., of Johns Hopkins Medical Institutions and lead investigator of the OmniHeart study.
The OmniHeart study did not address other types of diets such as the Atkins or Mediterranean diet.
The OmniHeart study was conducted at Johns Hopkins Medical Institutions and Brigham and Womens Hospital. The first participants started the protocol in 2003, and the last participants ended the study in June 2005.
NHLBI has long recommended changes in lifestyle, including following a heart healthy eating plan to reduce risk factors for heart disease. The DASH eating plan was developed through a series of clinical studies that showed that a dietary pattern rich in fruits, vegetables, fat-free or low-fat milk and milk products, and whole grains substantially reduced blood pressure and had other beneficial effects. The eating plan also includes lean meats, poultry, fish, legumes, and nuts and is low in saturated fats, cholesterol, sodium, and sweets and added sugars.
The new DASH Eating Plan menus are included in the book A Healthier You published by the U.S. Department of Health and Human Services. This newly released book is based on the 2005 Dietary Guidelines for Americans.
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