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(HealthNewsDigest.com) – DALLAS, July 18, 2011 – Milk and soy protein supplements were associated with lower systolic blood pressure compared to refined carbohydrate dietary supplements, in a study reported in Circulation: Journal of the American Heart Association.
The study’s results suggest that partly replacing refined carbohydrates
with foods or drinks high in soy or milk protein may help prevent and
treat high blood pressure, said Jiang He, M.D., Ph.D., lead researcher
of the study.
The randomized, controlled clinical trial is the first to document that
milk protein lowers blood pressure for people with pre-hypertension and
stage-1 high blood pressure.
Study participants who took a milk protein supplement had a 2.3
millimeters of mercury (mmHg) lower systolic blood pressure, compared
to when they took a refined carbohydrate supplement. Participants who
took a soy protein supplement had a 2.0 mmHg lower systolic blood
pressure when compared to the refined carbohydrate supplement.
Systolic blood pressure is the top number in a blood pressure reading
and gauges the pressure when the heart contracts. Refined carbohydrate
supplements were not linked to a change in systolic blood pressure.
The 352 adults in the study were at increased risk of high blood
pressure or had mild cases of the condition.
Previous studies have shown that a diet rich in low-fat dairy products
reduces blood pressure. Almost 75 million Americans have high blood
pressure, a “silent killer” that can cause heart attacks, heart
failure, strokes, kidney damage and other potentially fatal events.
“Some previous observational research on eating carbohydrates
inconsistently suggested that a high carbohydrate diet might help
reduce blood pressure,” said He, an epidemiologist at Tulane University
School of Public Health and Tropical Medicine in New Orleans, La. “In
contrast, our clinical trial directly compares soy protein with milk
protein on blood pressure, and shows they both lower blood pressure
better than carbohydrates.”
Participants were age 22 or older, with systolic blood pressure ranging
from 120 to 159 mmHg and diastolic blood pressure from 80 to 95 mmHg.
Each was randomly assigned to take 40 grams of soy protein, milk
protein or a refined carbohydrate supplement every day, for eight weeks
each. The supplements used were formulated in a way that allowed
researchers to compare the effects of soy protein, milk protein, and
refined complex carbohydrate on blood pressure without changing sodium,
potassium, and calcium.
Each eight-week phase was followed by a three-week washout period when
study participants did not take supplements. They took the three
supplements as identical powder supplements dissolved in liquid.
Blood pressure readings were taken three times at each of two clinical
visits before and two clinical visits after each eight-week phase,
yielding a net blood pressure change for each supplement period. The
study results showed no decrease in diastolic blood pressure.
“The systolic blood pressure differences we found are small for the
individual, but they are important at the population level,” He said.
Based on previous research, a 2 mmHg decrease in systolic blood
pressure could lead to 6 percent fewer stroke-related deaths, a 4
percent lower rate of heart disease deaths and a 3 percent reduction in
overall deaths among Americans.
Long-term studies would be needed to make specific recommendations for
dietary changes, He said.
Co-authors are: Marion R. Wofford, M.D.; Kristi Reynolds, Ph.D.,
M.P.H.; Jing Chen, M.D., M.Sc.; Chung-Shiuan Chen, M.S.; Leann Myers,
Ph.D.; Deborah L. Minor, Pharm.D.; Patricia J. Elmer, Ph.D.; Daniel W.
Jones, M.D.; and Paul K. Whelton, M.D., M.Sc. Individual author
disclosures are on the manuscript.
The National Heart, Lung, and Blood Institute funded the study.
Statements and conclusions of study authors published in American Heart
Association scientific journals are solely those of the study authors
and do not necessarily reflect the association’s policy or position.
The association makes no representation or guarantee as to their
accuracy or reliability. The association receives funding primarily
from individuals; foundations and corporations (including
pharmaceutical, device manufacturers and other companies) also make
donations and fund specific association programs and events. The
association has strict policies to prevent these relationships from
influencing the science content. Revenues from pharmaceutical and
device corporations are available at
www.americanheart.org/corporatefunding.
NR11 — 1099 (Circ/He)
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