July 8 (HealthDay News) -- Researchers say they have discovered that one of the most common amino acids in vegetable protein seems to lower blood pressure.
Analysis of data from an international diet study shows that a 4.72 percent higher intake of glutamic acid as a portion of total dietary protein correlates with a 1.5- to 3-point reduction in average systolic blood pressure (the higher of the two blood pressure readings, when the heart beats) and a 1- to 1.6-point lower diastolic pressure (the lower reading, when the heart rests between beats). The report appears online July 6 in advance of publication in an upcoming print issue of the journal Circulation.
The point difference might not sound like much, but high blood pressure is a leading risk factor for heart disease, stroke and other cardiovascular problems, and a reduction on that scale could cut stroke death rates by 6 percent and coronary heart disease deaths by 4 percent, said study author Dr. Jeremiah Stamler, professor emeritus of preventive medicine at the Feinberg School of Medicine at Northwestern University in Chicago.
However, the worry is that people could take the finding as a reason to pop glutamic acid pills rather than making vegetables a larger part of their diet, Stamler said.
"We make a clear statement that there are no data on supplements of glutamic acid to tell us anything one way or another about their value," Stamler said.
Protein, animal and vegetable, consists of chains of amino acids. Glutamic acid is the most common of those amino acids, accounting for 23 percent of vegetable protein and 18 percent of meat protein.
The relationship between higher glutamic acid intake and lower blood pressure seen in the study of 4,680 people in China, Japan, the United States and the United Kingdom was not unexpected, said Ian J. Brown, a research associate in epidemiology and public health at Imperial College London, and a member of the research team.
"It is compatible with earlier findings that a diet high in vegetable proteins, those found in beans, whole grains, rice, soy products and bread, is associated with lower blood pressure," Brown said.
"The fact that the most important amino acid in vegetable protein is related to blood pressure supports the inference that a diet high in vegetable protein and low in animal protein has favorable effects on blood pressure," Stamler added.
Similar but lesser effects on lowering blood pressure have been found for other amino acids more common in vegetable protein, such as proline, phenylalanine and serine, Brown said.
"The solution to improving blood pressure is not based around a single nutrient," he said. "We are looking at a whole series of dietary elements that act together. Combined, they have a large effect."
But diet is not the only factor to be considered in attacking high blood pressure, Stamler said.
"We must also consider obesity, high salt intake, high alcohol intake and high potassium intake, among other risk factors," he said.
Still, the study provides evidence why the Dietary Approaches to Stop Hypertension (DASH) diet, developed by the U.S. National Institutes of Health, reduces blood pressure, Stamler said. The DASH diet is rich in fruits, vegetables, whole grains, lean poultry, nuts and beans.
"It's just as mothers and grandmothers have been saying for years," Brown said. "Eat your vegetables, avoid fatty foods, avoid excess alcohol."
SOURCES: Jeremiah Stamler, M.D., professor emeritus, preventive medicine, Feinberg School of Medicine, Northwestern University, Chicago; Ian J. Brown, Ph.D., research associate, epidemiology and public health, Imperial College, London; July 6, 2009, Circulation online