Replacing Some Carbohydrates
with Protein and Unsaturated Fat May Enhance Heart
Health Benefits
Dallas, Nov 15—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 NHLBI’s 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.
These new OmniHeart study results do not represent
new guidelines for healthy eating and the proportions
of carbohydrate, protein, and fat for all three diets
are all within the ranges recommended by the U.S.
Dietary Guidelines for Americans and other national
public health organizations. Earlier in 2005, the
U.S. Department of Health and Human Services incorporated
NHLBI’s DASH eating plan as one option within
the U.S. Dietary Guidelines.
All of the studied diets are a vast improvement over
the typical American diet which can be high in saturated
fat and low in essential nutrients, according to NHLBI
Director Elizabeth G. Nabel, M.D.
“This study builds on an established body of
evidence that shows following a dietary pattern lower
in saturated fat, such as the DASH eating plan, can
go a long way toward improving overall heart health.
With these new data, we have been able to incorporate
even more flexibility into the DASH eating plan by
providing additional options for people seeking to
improve their heart health through healthier eating,”
said Nabel.
The study results reinforce the health benefits of
following a DASH-type eating plan and suggests that
tweaking certain components within that plan—protein
and unsaturated fat—may yield benefits for specific
risk factors. Compared with the study diet containing
more carbohydrates, the diet with greater protein:
- lowered blood pressure, LDL “bad”
cholesterol, and triglycerides, and
- lowered HDL “good” cholesterol.
- The diet with more unsaturated fat, primarily
monounsaturated fat:
- lowered blood pressure and triglycerides,
- raised HDL, and
- did not lower LDL.
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:
- The diet emphasizing carbohydrates contained 58
percent of calories from carbohydrates and 15
percent of calories from protein. In addition,
it contained 21 percent of calories from unsaturated
fat. The other two diets reduced carbohydrate
to 48 percent of calories.
- The diet emphasizing protein increased the protein
to 25 percent of calories. To increase protein,
mostly plant sources, such as beans and nuts,
were used, although poultry, egg substitutes,
and fat-free or low-fat milk products were also
used. Like the carbohydrate diet, it contained
21 percent of calories from unsaturated fat.
- The diet emphasizing unsaturated fat used primarily
fats and oils rich in monounsaturated fat, like
olive oil, to increase unsaturated fat to 31 percent
of calories. Like the carbohydrate diet, it contained
15 percent of calories from protein.
“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 Women’s
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.
Resources:
http://www.nhlbi.nih.gov/health/public/heart/hbp/dash/index.htm
http://www.healthierus.gov/dietaryguidelines/
http://www.hhs.gov/news/press/2005pres/20051024.html
To interview a scientist about this study, contact
the NHLBI Communications Office at (301) 496-4236.
NHLBI is part of the National Institutes of Health
(NIH), the Federal Government’s primary agency
for biomedical and behavioral research. NIH is a component
of the U.S. Department of Health and Human Services.
NHLBI press releases and other materials including
information about the DASH plan and eating for heart
health are available online at www.nhlbi.nih.gov.
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