Trade Carbs for Proteins: Heart Healthy?
Researchers Find Small Dietary Shifts Can Reap Heart and Blood Pressure Benefits
Nov. 14, 2005 -- Trading in a slice of bread for a handful of nuts or
drizzle of olive oil may help in the fight against high blood pressure and
A new study suggests that swapping out a small amount of carbohydrates in an
already heart-healthy diet for either protein-rich foods or unsaturated fats
may provide additional benefits in lowering heart disease risk.
Researchers compared the effects on blood pressure and cholesterol levels of
a healthy carbohydrate-rich diet -- based on the
-- to similar
diets with about 10% of the carbohydrates replaced with protein from mostly
plant sources or unsaturated fats.
Reducing Heart Risk
"All three diets reduced overall heart disease risk, lowering blood
pressure and improving cholesterol levels," says researcher Lawrence Appel,
MD, MPH, professor of medicine at the Johns Hopkins School of Medicine, in a
news release. "But the protein and monounsaturated fat diets had an edge
over the carbohydrate-rich diet."
The protein-rich diet reduced heart disease risk by 21%, and the
monounsaturated-fat-rich diet reduced it by almost 20%, compared with the 16%
reduction found with the carbohydrate-rich diet.
"Our study provides strong evidence that replacing some carbohydrate
with either protein or monounsaturated fat has important health benefits,"
says Appel. "There is already agreement that reducing saturated fat lowers
risk for heart disease, but the question of which macronutrient [fat, protein,
or carbohydrate] to emphasize has been controversial."
Trade in a Few Carbs for Heart Benefits
Researchers stress that none of the diets studied was low in carbohydrates
or very high in protein. Instead, all three of the diets were low in saturated
fat (the fat found in meat and dairy products), cholesterol, and sodium; the
diets were rich in fruits, vegetables, fiber, potassium, and other minerals at
the recommended levels.
In the high-protein diet, researchers replaced approximately 10% of the
total daily calories from carbohydrates with protein. About 50% of the protein
came from plant sources, such as beans, nuts, seeds, and some grains. The
unsaturated fat diet was enriched with monounsaturated fats and included olive
and canola oils, as well as some nuts and seeds.
In the study, which appears in The Journal of the American Medical
Association, researchers compared the effects of the three diets in 164
adults who either had high blood pressure or were on the verge of having it.
All of the participants followed each diet with all the necessary foods
provided to them for six weeks, with two to three weeks between each different
diet. Food was prepared in research kitchens.
Blood Pressure and Cholesterol Changes
Researchers found that blood pressure and cholesterol levels improved after
each diet phase compared with the start of the study. But the benefits achieved
with the protein-rich and monounsaturated-fat-rich diets were greater than with
the DASH-based diet alone.
In an editorial that accompanies the study, Myron H. Weinberger, MD, of
Indiana University Medical Center, says the results of this study may be
difficult to apply to the public.
He says the people in this study were highly motivated to follow the diets
because of their blood pressure status and the fact that all of the foods were
provided to them.
"Although the benefit of blood pressure reduction in those in the
prehypertensive group is clear," Weinberger says the ability to control
high blood pressure adequately in the people with existing hypertension is not
clear. "It is likely that more than diet will be required to reach goal
blood pressures for the majority of these individuals."