The optimal dietary distribution of protein, unsaturated fat, and carbohydrate for reducing cardiovascular risk has yet to be determined. The Dietary Approaches to Stop Hypertension (DASH) diet is a low-sodium diet rich in fruits, vegetables, and low-fat dairy products designed to lower blood pressure . But the DASH diet is carbohydrate-rich, and recent research suggests that diets rich in protein or monounsaturated fats (e.g., olive oil, nuts, seeds) may reduce the risk for cardiovascular disease.

A new study in the November 16, 2005 issue of the Journal of the American Medical Association examined the effect of varying the protein, unsaturated fat, and carbohydrate composition of the DASH diet on cardiovascular risk factors. The researchers found that diets higher in proteins and unsaturated fats resulted in greater improvements in blood pressure and cholesterol levels.

About the Study

Researchers assigned 164 adults with elevated blood pressure to follow each of following diets for six weeks, with 2-4 week “washout periods” between diets:

  • Carbohydrate diet – 27% fat (6% saturated and 21% unsaturated), 58% carbohydrate, and 15% protein (based on the DASH diet)
  • Protein diet – 27% fat (6% saturated and 21% unsaturated), 48% carbohydrate, and 25% protein
  • Unsaturated fat diet – 37% fat (6% saturated and 31% unsaturated), 48% carbohydrate, and 15% protein

The diets were low in saturated fat, cholesterol, and sodium, and rich in fruits, vegetables, fiber, and potassium. The study foods were provided to the participants, and calorie levels were adjusted to keep each participant’s weight constant. The researchers collected the participants’ blood pressure and cholesterol levels before and after each diet.

All diets improved blood pressure and cholesterol levels. Compared with the carbohydrate diet, the protein diet resulted in greater decreases in blood pressure, low-density lipoprotein (LDL, or “bad”) cholesterol, high-density lipoprotein (HDL, or “good”) cholesterol, and triglycerides. Compared with the carbohydrate diet, the unsaturated fat diet resulted in greater decreases in blood pressure and triglycerides, an increase in HDL cholesterol, and no effect on LDL cholesterol.

These results are limited because changes in each diet lasted only six weeks. Ideally, the researchers would have followed the participants for a number of years to determine if their risk for actual cardiovascular events (e.g., strokes, heart attacks) was affected.

How Does This Affect You?

These findings suggest that replacing some of the carbohydrates in a DASH-like diet with protein or unsaturated fats can further lower blood pressure, improve cholesterol levels, and reduce cardiovascular disease risk. It is not clear which diet was superior, since the protein diet lowered HDL (“good”) cholesterol and the unsaturated fat diet had no affect on LDL cholesterol.

The complex meal plans used in this study may be hard to adhere to in the real world. If you want to improve your cardiovascular health, aim to incorporate a variety of plant proteins (e.g., legumes, grains, nuts, seeds) and monounsaturated fats (e.g., olive, canola, and safflower oils) into a diet that is rich in fruits, vegetables, and low-fat dairy products, and low in saturated fat and sodium.