July 22, 2011

Protein supplementation lowers blood pressure

In an article published online on July 18, 2011 in Circulation: Journal of the American Heart Association, Jiang He, MD, PhD and associates report the outcome of a crossover trial which found that milk and soy protein supplements lower systolic blood pressure among those in the early stages of hypertension. The trial is the first to document a blood pressure-lowering benefit for milk protein among those with prehypertension or stage-1 high blood pressure.

A team led by Dr He, who is an epidemiologist at Tulane University School of Public Health and Tropical Medicine in New Orleans, divided 352 adults with prehypertension or stage 1 high blood pressure to receive 40 grams of soy or milk protein, or a refined carbohydrate supplement daily for eight weeks followed by a three week wash-out period in which no supplements were given. The subjects then participated in two additional treatment phases in which they received supplements that had not previously been administered. Blood pressure was measured during two visits prior to each treatment phase and twice following treatment.

The trial revealed a reduction in systolic blood pressure associated with protein, but not carbohydrate, supplementation. Participants who received soy protein experienced a 2.0 mmHg decrease in systolic blood pressure, while those who received milk protein had a 2.3 mmHg reduction. Prior research has associated a 2 mmHg reduction in blood pressure with a 6 percent decrease in deaths due to stroke. "The systolic blood pressure differences we found are small for the individual, but they are important at the population level," Dr He remarked.

"Some previous observational research on eating carbohydrates inconsistently suggested that a high carbohydrate diet might help reduce blood pressure," Dr He noted. "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."

"The results from this randomized, controlled trial indicate that both soy and milk protein intake reduce systolic blood pressure compared with a high-glycemic-index refined carbohydrate among patients with prehypertension and stage 1 hypertension," the authors conclude. "Furthermore, 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."

High blood pressure

While searching for a natural agent to help optimize blood pressure, researchers hydrolyzed (or split) the milk protein known as casein and isolated the C12 peptide. Clinical studies now show that the C12 peptide is a natural ACE inhibitor that has specific blood pressure-lowering effects (Karaki H et al 1990).

A small study conducted in the United States demonstrated C12 peptide’s effectiveness in helping to normalize high blood pressure. This randomized, double-blind, placebo-controlled, crossover study examined 10 men and women (average age, 50 years) who had an average blood pressure of 152/98 mm Hg and were not taking antihypertensive medications. Each subject took a placebo for 6 days and then a single dose of either 200 mg or 400 mg C12 peptide. Blood pressure was monitored via a small blood pressure unit that each subject wore throughout the day. In the 200-mg and 400-mg treatment groups, systolic pressure declined significantly by an average of 2.4 mm Hg and 4.5 mm Hg, respectively, while diastolic pressure dropped by an average of 4.4 mm Hg and 6.5 mm Hg, respectively (Townsend RR et al 2004). The study results demonstrate that the C12 peptide has a notable impact on blood pressure after only a single dose.

A Japanese study sought to evaluate the longer-term benefits of supplementing with the C12 peptide. Eighteen mildly hypertensive subjects, with a mean blood pressure of 141/99 mm Hg, received 200 mg/day of the C12 peptide for 4 weeks. The researchers recorded significant reductions—4.6 mm Hg in systolic blood pressure and 6.6 mm Hg in diastolic blood pressure. Blood pressure declined gradually over the 4-week study period. A gradual decline is indicative of a healthy decline, as opposed to a dramatic drop that could cause dizziness or fainting. When treatment was halted, the subjects’ blood pressure began to return to the baseline levels that were recorded prior to treatment. The researchers also observed that the C12 peptide appears to have long-lasting effects. Even 2 weeks after treatment ended, diastolic blood pressure levels were still significantly lower than at baseline levels (Sekiya S et al 1992). No unfavorable side effects were reported.

Soy is a high-protein, low-fat food derived from soybean. Protein comprises nearly half its calories, and carbohydrate and fat roughly equal the other half. Soy holds only a trace amount of saturated fat and no cholesterol. In search of a natural approach to treating high blood pressure, a recent study addressed the effects of increased dietary soy protein on blood pressure. Researchers confirmed previous studies that showed higher intake of vegetable protein lowers blood pressure (He J et al 2005).

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