Another soy protein/hypertension reduction article. From Medscape.

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Another soy protein/hypertension reduction article. From Medscape.

Laurie Barclay, MD;

July 5, 2005 - Soy protein supplements can significantly reduce blood

pressure in hypertensive patients, according to the results of a randomized,

double-blind study published in the July 5 issue of the ls of Internal

Medicine. The editorialists suggest that recommending soy protein would be

premature because of incomplete evidence, but they do advocate the Dietary

Approaches to Stop Hypertension (DASH) diet.

" Epidemiologic studies suggest that vegetable protein intake is inversely

related to blood pressure, " write Jiang He, MD, PhD, from Tulane University

in New Orleans, Louisiana, and colleagues. " The effect of dietary

macronutrients on blood pressure has not been well studied, although

clinical trials indicate that diets rich in fruits, vegetables, and low-fat

dairy products and with reduced saturated and total fat (DASH diet) lower

blood pressure. "

In three communities in the People's Republic of China, 302 participants

with an initial untreated systolic blood pressure of 130 to 159 mm Hg,

diastolic blood pressure of 80 to 99 mm Hg, or both were randomized to

receive 40 g of isolated soybean protein supplements daily or complex

carbohydrate control for 12 weeks. Age range was 35 to 64 years. Mean

systolic blood pressure was 135.0 ± 10.9 mm Hg, and diastolic blood pressure

was 84.7 ± 6.9 mm Hg at baseline.

Of the 302 participants, 91.4% completed the 12-week trial. Neither group

reported significant adverse effects. Compared with the control group, the

net blood pressure changes in the soy group after the intervention

were -4.31 mm Hg systolic (95% confidence interval [CI], -2.11 to -6.51 mm

Hg; P < .001) and -2.76 mm Hg diastolic (95% CI, -1.35 to -4.16 mm Hg; P <

..001), respectively.

In participants with hypertension, the net changes in systolic and diastolic

blood pressure were -7.88 mm Hg (95% CI, -4.66 to -11.1 mm Hg) and -5.27 mm

Hg (95% CI, -3.05 to -7.49 mm Hg), respectively. In participants without

hypertension, the net changes were -2.34 mm Hg (95% CI, 0.48 to -5.17 mm Hg)

and -1.28 mm Hg (95% CI, 0.52 to -3.07 mm Hg).

Study limitations were inability to determine whether the blood pressure

reduction was related to protein or isoflavones in soybean and failure to

control dietary nutrient intake as strictly as is possible in a feeding

study.

" Soybean protein supplementation resulted in a reduction in systolic and

diastolic blood pressure, " the authors write. " These findings suggest that

increased intake of soybean protein may play an important role in preventing

and treating hypertension. "

However, they note that 40 g of soybean protein is approximately equivalent

to one soy burger plus one to two cups of soy milk, which may be difficult

to consume daily.

The Tulane University Health Sciences Center; National Heart, Lung, and

Blood Institute in Bethesda, land; and the National Ninth Five-Year Plan

Key Program from the Ministry of Science and Technology of the People's

Republic of China supported this study. The authors report no potential

financial conflicts of interest.

In an accompanying editorial, A. Cutler, MD, and Eva Obarzanek, PhD,

from the National Heart, Lung, and Blood Institute, cite some evidence of an

association between soy protein and increased risk for bladder cancer. They

wonder if a mixed vegetable protein product would produce the same blood

pressure lowering effect without increased bladder cancer risk. An ongoing

large trial should help address some of these issues, with results

anticipated later this year.

" We should require good evidence of benefit and safety before recommending

soybean protein to the much larger population that is at risk for

hypertension, " Drs. Cutler and Obarzanek write. " However, higher protein

intake may prove to be healthful, and we agree with current blood pressure

control guidelines that recommend diets higher in total protein, such as the

DASH diet. "

Ann Intern Med. 2005;143:1-9, 74-75

Reviewed by D. Vogin, MD