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Wednesday October 29, 2008 (foodconsumer.org) -- Eating a salty diet can increase your blood pressure. But eating grapes may counteract the effect of salt and help lower your blood pressure and protect against heart disease, according to a new study.



The study led by researchers at the University of Michigan Cardiovascular Center found rats fed grape-rich diet powder had lower blood pressure, better heart function, reduced inflammation and fewer signs of heart muscle damage.



The researchers attributed the benefits to the high level of antioxidants in grapes.



In the study, Mitchell Seymour and colleagues tested the effect of regular table grapes (a combination of green, red, and black grapes) mixed into the rat diet in rats fed either a high salt or low salt diet. The rats were prone to developing high blood pressure when fed a salty diet.



After 18 weeks of dietary intervention, all lab tests suggested that the rats on the grape diet had better cardiovascular health indicated by lower blood pressure and better heart function and reduced inflammation than the rats on a diet without grapes among others.



The researchers found the blood pressure medicine hydrazine also lowered blood pressure in the rats on a salty diet, but their hearts were not as much protected from damage as those on the grape diet were.



"These findings support our theory that something within the grapes themselves has a direct impact on cardiovascular risk, beyond the simple blood pressure-lowering impact that we already know can come from a diet rich in fruits and vegetables." said Seymour.



U-M heart surgeon Steven Bolling, M.D., senior author of the study, noted that the animals were in a situation similar to the one millions of Americans face today and they ate salty diet and had high blood pressure and eventually developed heart failure due to prolonged hypertension.



Bolling said they believed the active ingredients in grapes are likely the flavanoids, but the exact mechanisms behind the protective effect remain unknown.



He warned though that people who want to lower their blood pressure and other heart risk should cut down on the amount of salt they ingest through food and beverages.



The researchers found the rats on the high-salt diet supplemented with grape or hydrazine eventually developed high blood pressure over time. It's only that the rats on the grape diet had lower systolic blood pressure than other rats on a high salt diet that did not receive grapes.



"There is, as we now know, a great variability, perhaps genetic even, in sensitivity to salt and causing hypertension," he said. "Some people are very sensitive to salt intake, some are only moderately so, and there are perhaps some people who are salt resistant. But in general we say stay away from excess salt."



High blood pressure is common in developed countries. A new study in the Nov. 2008 issue of hypertension found incidence of high blood pressure increased from 50.3 to 55.5 percent between 1994 and 2004 while the rate of hypertension increased from 32.3 to 36.1 percent.



In addition to grapes, foods like cocoa, vegetable protein, garlic, onions among others may help lower blood pressure while high fat, high salt and high caffeine may increase blood pressure, numerous previous studies suggested.