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To Improve Heart Health, Replace Bread with Beans and Oil?

Swapping some of your carbs for protein or healthy fats may be just the right move for a healthier heart, say researchers.

New findings, published in November 2005 in the Journal of the American Medical Association, show that replacing some carbohydrates, like a bowl of pasta, with protein or monounsaturated fat, such as a black bean taco, may help to reduce your overall risk of heart disease.

"[These changes] can lower blood pressure, improve cholesterol levels and reduce heart disease risk," said Dr. Lawrence Appel, lead author of the study and professor of medicine at Johns Hopkins University.

To test the heart benefits of different diets, the researchers recruited 164 adults with either high blood pressure or the early signs of this problem. The participants were divided into three groups, based on diets that emphasized carbohydrates, protein or unsaturated fats.

In the protein-rich diet, about half of the proteins eaten were derived from plant sources, like beans, nuts and vegetable-based meat substitutes, which tend to be lower in fat than animal sources of protein. In the unsaturated-fat-rich diet, most of the fat was of the monounsaturated kind found in olives, peanuts and canola oil. This type of fat is considered to be healthy since eating such foods can lower artery-clogging cholesterol.

For example, a higher-carb lunch would consist of a chicken sandwich with mayonnaise on whole wheat bread, while the unsaturated-fat-rich dieters would eat their chicken sandwich with olive-oil margarine and barbeque sauce on white bread. The protein-rich dieters would eat a veggie burger instead with barbeque sauce on a hamburger roll.

Snacks for the groups varied, too, with trail mix featured in the carb diet, cottage cheese for the protein eaters and olive oil potato chips for the unsaturated fat group.

After staying on the diets for six weeks and maintaining a constant body weight, researchers found that all of the diets helped to lower the participants' blood pressure and bad, or LDL, cholesterol levels. However, those on the high protein and high unsaturated fat diet showed even lower levels. Overall, these two diets led to a significantly lower risk of heart disease than the carbohydrate diet.

Previous studies have shown that consuming high amounts of salt and alcohol as well as being overweight can all affect blood pressure and heart disease risk, but this is the first study to show that macronutrients, like proteins and fats, may affect blood pressure in a positive way, say the authors from the OmniHeart Collaborative Research Group, which conducted the study.

The authors caution, however, that all of the participants were put on meal plans that are healthier than the typical American diet, possibly explaining why all three diets helped to improve the participants' heart health.

"All three diets are good; it's just that two diets are somewhat better," said Dr. Frank Sacks from the study center at Brigham & Women's Hospital at Harvard Medical School in a press release. "Most of us in public health would be happy if people were consuming the carbohydrate diet, which is much better than what most Americans typically eat."