Substituting protein or monounsaturated fats for carbohydrates in a healthy diet will reduce heart disease risk, according to the OmniHeart Collaborative Research Group.

OmniHeart compared the effects of three healthy diets on blood pressure and cholesterol levels in 164 adults with elevated blood pressure – systolic of 120–159 mm/Hg or diastolic at 80–99 mm/Hg.

“While we know that lowering dietary saturated fat reduces cardiovascular risk, there is less certainty about which macronutrient balance offers optimum risk reduction,” said Dr. Lawrence J. Appel, a principal investigator of OmniHeart and professor of medicine at Johns Hopkins University.

“OmniHeart offers evidence that substituting carbohydrates with protein or with unsaturated fat can lower blood pressure, improve cholesterol levels, and reduce heart disease risk.”

All diets were low in saturated fat and healthier than the average diet prior to start of the study. One diet was rich in carbohydrates and is essentially similar to the Dietary Approaches to Stop Hypertension (DASH) diet which emphasizes fruits, vegetables, and low-fat or fat-free dairy products.

The second diet shifted 10 percent of its calories to protein, compared to the carbohydrate diet. The third shifted 10 percent of its calories to unsaturated fat, predominantly monounsaturated fat (found in peanuts, olives, and oils such as canola oil). Study participants were randomized to one of the three diets for six weeks at a time.

“In comparison to baseline levels (obtained when participants were eating their own food), all three diets lowered systolic blood pressure by 8.2–9.5 mm/Hg and LDL-C by 11.6–14.2 mg/dL,” Appel said.

When compared to the carbohydrate diet, the protein diet reduced systolic blood pressure, lowered LDL, and reduced triglycerides by nearly 16mg/dL. (However, HDL decreased by 1.4 mg/dL.) The unsaturated fat diet reduced systolic blood pressure and while it had no significant effect on LDL, it raised HDL levels and lowered triglyceride levels.

The OmniHeart study demonstrated that protein and unsaturated fat diets offer the lowest CHD risk. There was a 16 percent risk reduction in the carbohydrate diet, but nearly 20 percent risk reduction in the unsaturated fat and protein diets.

“OmniHeart provides convincing evidence that the amount of carbohydrates, protein and fat people eat influence risk,” said Appel. OmniHeart data can help policy makers in making public health recommendations, as well as assist clinicians in advising patients. Further information is available at www.omniheart.org.