'Tofu' Soothes Blood Pressure

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In individuals with prehypertension or stage I hypertension, soy and milk

protein supplementation reduced systolic blood pressure, a randomized trial

showed.

Systolic blood pressure dropped by about 2 mm Hg during eight weeks of

supplementation with soy and milk protein, compared with carbohydrate

supplementation, which had no effect, according to Jiang He, MD, PhD, of

Tulane University in New Orleans, and colleagues.

None of the supplements had an effect on diastolic blood pressure, the

researchers reported online in *Circulation: Journal of the American Heart

Association*.

" These study findings may have important public health and clinical

implications, " they wrote, noting that it was estimated previously that a

2-mm Hg drop in systolic blood pressure at the population level could lead

to a 6% reduction in stroke mortality, 4% reduction in coronary heart

disease mortality, and 3% reduction in all-cause mortality.

Although observational studies have suggested that blood pressure is reduced

with higher dietary protein intake, the results have been inconsistent.

To explore the issue, He and colleagues initiated the Protein and Blood

Pressure (ProBP) study, a randomized, double-blind, crossover trial

involving 352 adults with mildly elevated blood pressure.

At baseline, systolic blood pressure was between 120 and 159 mm Hg and

diastolic pressure was between 80 to 95 mm Hg; 18.5% of participants had

hypertension.

There were three intervention phases, each lasting eight weeks and separated

by a three-week washout period. The participants took one of the following

powdered supplements during each phase, in random order: 40 grams/day of soy

protein, milk protein, or carbohydrate (as the control).

The researchers provided individualized dietary recommendations to maintain

a consistent total energy intake during the interventions. The participants

were asked to not make any changes in physical activity, alcohol

consumption, and sodium intake.

Three seated blood pressure measurements were taken with a random-zero

sphygmomanometer at each of two baseline and two termination visits during

each of the three intervention phases.

During the study, there were no differences based on the supplement taken in

intake of total energy, fat, saturated fat, sodium, potassium, and calcium.

HDL cholesterol level was significantly higher with soy protein than with

the other two supplements (*P*=0.03), but body weight, fasting plasma

glucose, and other lipid parameters were consistent between the three

supplements.

Systolic blood pressure dropped significantly in both of the protein

supplementation groups, with no change in the carbohydrate group. The net

reductions in the soy and milk protein groups compared with the carbohydrate

group were 2.0 and 2.3 mm Hg, respectively (*P*≤0.002 for both).

There were no differences in blood pressure reduction between the soy and

milk protein groups.

The researchers noted that soy protein is high in dietary phosphorus, which

has been inversely associated with blood pressure. And milk protein is rich

in angiotensin-I-converting enzyme inhibitory peptides, including casokinins

and lactokinins, which have been shown to reduce blood pressure.

" These findings suggest that partially replacing carbohydrate with soy or

milk protein might be an important component of nutrition intervention

strategies for the prevention and treatment of hypertension, " the authors

wrote.

Side effects were largely similar among the three supplements, with no

differences in rates of a change in appetite, upset stomach or nausea,

stomach pain or burning, diarrhea, constipation, red blood in the stool or

blackened stools, frequent urination, excessive gas, excessive thirst, and

change in sexual drive.

Participants reported more bad taste during the soy protein phase (16.4%

versus 10.5% with milk protein and 8% with carbohydrates) and more belching

during the soy and milk protein phases (16.5% and 15.7%, respectively) than

during the carbohydrate phase (7.7%).

The researchers acknowledged that the study was limited by the relatively

short duration of intervention, the use of a high-glycemic-index

carbohydrate supplement as a control, and the lack of testing for a

dose-response relationship between dietary protein and blood pressure.

*From the American Heart Association:*

- Soy, Protein, Isoflavones, and Cardiovascular Health: An American Heart

Association Science Advisory for Professionals from the Nutrition

Committee<http://circ.ahajournals.org/content/113/7/1034.full.pdf>

*Primary source: *Circulation: Journal of the American Heart Association

Source reference:

He J, et al " Effect of dietary protein supplementation on blood pressure: A

randomized, controlled trial " *Circulation* 2011; DOI:

10.1161/CIRCULATIONAHA.110.009159.<http://circ.ahajournals.org/content/early/201\

1/07/18/CIRCULATIONAHA.110.009159.abstract>

--

Ortiz, MS, RD

*The FRUGAL Dietitian* <http://www.thefrugaldietitian.com>

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