Getting More Protein from Plants May Lower Blood Pressure

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PEOPLE WHO CONSUME regular daily portions vegetables, whole grains and fruit tend to have healthier blood pressure levels than their more carnivorous peers, according to a new British study. The findings bolster recommendations that adults eat more plant-based foods for the sake of their cardiovascular health.

The study, published in the Archives of Internal Medicine, found that among nearly 4,700 middle-aged adults in four countries, those who ate more vegetable protein tended to have lower blood pressure. The apparent benefit was independent of other factors, such as exercise, sodium intake and body weight, according to Paul Elliott, MB, PhD, of Imperial College in London, the study's lead author. Elliott added that the findings lend support to recommendations to eat more plant-based foods.

The International Study on Macronutrients and Blood Pressure (INTERMAP) Cooperative Research Group recruited 1,145 participants from Japan, 839 from China, 501 from England and 2,195 from the US. Blood pressure was measured at four visits over three- to six-week intervals. At each visit the participants completed detailed diaries describing total food intake over the previous 24 hours. Urine specimens were collected at the first and third examinations.

Overall, the study found, average blood pressure levels dipped as vegetable protein intake increased. The opposite was true of animal protein intake. Participants for whom vegetable protein represented about 9% of total caloric intake had systolic blood pressures that were on average 2.14 mm Hg lower and diastolic pressures that were 1.35 mm Hg lower than those whose diets were not so rich in vegetable protein. Even after adjusting for height and weight, the differences were still significant; systolic pressure averaged 1.11 mm Hg lower and diastolic pressure was 0.71 mm Hg lower.

Blood pressure above optimal (120/80 mmHg) has been established as a major cardiovascular disease risk factor. The Dietary Approaches to Stop Hypertension, or DASH, Eating Plan, considered the best diet against high blood pressure, is low in sodium and fat, and emphasizes low-fat dairy, fruits and vegetables. The INTERMAP findings on vegetable protein underscore the effectiveness of that element of the DASH plan.

The study authors theorized that the association between vegetable protein and blood pressure may be explained by the action of amino acids. "We found significant differences in the amino acid content of diets predominating in vegetable protein compared with those predominating in animal protein," they wrote. That difference may explain the opposing effects of animal and vegetable protein.

By eating a significant amount of vegetable protein, people tend to take in high amounts of fiber and magnesium, which may account for at least some of the positive blood pressure effects. Vegetable proteins also contain specific amino acids--the "building blocks" of protein--that research suggests help control blood pressure.

Although a definitive explanation of the blood pressure benefits requires further study, the authors of the INTERMAP study concluded that it is "consistent with current recommendations that a diet high in vegetable products be part of a healthy lifestyle for prevention of high blood pressure and related chronic diseases."

TO LEARN MORE: Archives of Internal Medicine, Jan. 9, 2006. Free abstract at . American Heart Association-High Blood Pressure .

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