Dietary Protein and its Effect on Hypertension

This study compares the effect of animal and vegetable protein on blood pressure in adults. In this study, 352 healthy adults with stage 1 hypertension participated. For 8 weeks, they consumed either milk or soy protein, or carbohydrate supplements. Baseline and end values of hypertension in these adults were recorded. Unlike carbohydrate consumption, protein consumption showed significant reduction in systolic (upper) blood pressure and non-significant reduction in diastolic (lower) value. The reductions for vegetable and animal proteins were not significantly different. These findings suggest that replacing carbohydrates in daily diet with protein might be an important component of nutrition intervention strategies for the prevention and treatment of hypertension.

Hypertension (high blood pressure) is on the rise across the world, together with the risk of heart disease and death. It is expensive to treat hypertension and related disorders, but providing preventive measures for these disorders is the best solution. The most recommended method of preventing hypertension is making positive changes in lifestyle. “Physical activity, weight reduction, dietary sodium reduction, moderation of alcohol consumption, potassium supplementation, and consumption of a diet rich in fruits, vegetables, and low-fat dairy products, along with reductions in saturated and total fat, have been recommended as effective approaches for the prevention of hypertension.” This study analyzes the effect of vegetable and animal protein intake on hypertension in adults.

* Men and women over 22 years of age with blood pressure 120 to 159 mm Hg/80 to 95 mm Hg were selected according to predetermined criteria. They were divided into three sequences.
* Sequence A received 40 g of soy protein for 8 weeks, then 40 g of milk protein for 8 weeks, and finally 40 g of complex carbohydrate for 8 weeks. The sequence was changed for the other two groups. Between each eight-week period, there was a three-week washout period.
* The body mass index, height, as well as baseline and termination visit blood pressure values were recorded.
* Urine samples at the beginning and end of the experiments were tested for excretion of sodium, urea, and so on.

* The overall protein intake had significantly increased by soy/milk protein supplements, while reducing the overall intake of carbohydrates. The intake of fat or total calories was not significantly different.
* Urea nitrogen excretion through urine increased with the increased dietary protein compared with the carbohydrate supplementation phase. No change was seen in excretion of sodium, potassium, and so on.
* The upper value of blood pressure reduced by 1.5 mm Hg during soy protein consumption; it reduced by 1.8 mm Hg during milk protein consumption; and no change was observed during carbohydrate consumption. The reductions in the lower value of blood pressure were not notable.
* The differences in the reductions in blood pressure values by milk or soy protein consumption were not significant.

Shortcomings/Next steps
The duration of the study is too short, despite the washout period. The control supplements used to balance the protein diet were high-glycemic index carbohydrates, which would have affected the blood pressure values independently. Tests are required to be conducted to confirm whether a change in the dosage of protein supplements would affect the values of blood pressure.

The study shows that eating vegetable or animal proteins is beneficial in reducing the upper value (systolic) of blood pressure compared to consumption of carbohydrates. Since the reduction by 2 mm Hg in the upper value is known to reduce the risk of stroke by 6 percent, heart attack by 4 percent, and death by 3 percent, this is noteworthy information for people looking to acquire healthier lifestyles. This study systematically compares the effects of the two types of proteins, proving the benefits of proteins in a vegetarian diet. It also proves that the beneficial effects are due to the protein component of the diet and not due to the mineral component (sodium and potassium).

For More Information:
Effect of Dietary Protein Supplementation on Blood Pressure
Publication Journal: Circulation, August 2011
By Jiang He, MD, PhD; Marion R Wofford, MD; Tulane University School of Medicine, New Orleans, Louisiana; University of Mississippi Medical Center, Jackson

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