Nine servings of grapes a day - or taken as a supplement - may save your heart. The effect is thought to be due to the high level of phytochemicals – naturally occurring antioxidants – that grapes contain.

The researchers studied the effect of regular table grapes (a blend of green, red, and black grapes) that were mixed into the animal diet in a powdered form, as part of either a high- or low-salt diet.

In all, after 18 weeks, the rats that received the grape-enriched diet powder had lower blood pressure, better heart function, reduced inflammation throughout their bodies, and fewer signs of heart muscle damage than the rats that ate the same salty diet but didn’t receive grapes.

The rats that received the blood-pressure medicine, hydrazine, along with a salty diet also had lower blood pressure, but their hearts were not protected from damage as they were in the grape-fed group.

 

Says Mitchell Seymour, M.S., who led the research as part of his doctoral work in nutrition science at Michigan State University, “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.”

Millions of Americans, who have high blood pressure related to diet, develop heart failure over time because of prolonged hypertension.

“The inevitable downhill sequence to hypertension and heart failure was changed by the addition of grape powder to a high-salt diet,” he says.

“Although there are many natural compounds in the grape powder itself that may have an effect, the things that we think are having an effect against the hypertension may be the flavanoids – either by direct antioxidant effects, by indirect effects on cell function, or both. These flavanoids are rich in all parts of the grape - skin, flesh and seed, all of which were in our powder,” Bolling explains.

“Though it’s true that your mom told you to eat all your fruits and your vegetables, and that we are learning a lot about what fruits, including grapes, can do in this particular model of hypertension and heart failure, we would not directly tell patients to throw all their pills away and just eat grapes,” says Bolling.

However, research on grapes and other fruits containing high levels of antioxidant phytochemicals continues to show promise. So does research on the impact of red wine on heart health, though that issue is also far from settled.

In the meantime, Bolling says, people who want to lower their blood pressure, reduce the risk of heart failure, or help their weakened hearts retain as much pumping power as possible should follow tried-and-true advice: Cut down on the amount of salt you get through your food and drink.

“There is, as we now know, a great variability, perhaps genetic even, in sensitivity to salt and causing hypertension,” he says. “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.”

He notes that the popular DASH diet, which is low in salt and high in fruits and vegetables, has been proven to reduce mild high blood pressure without medication.

The dose of whole table grape powder that was consumed in the study was roughly equivalent to a person eating nine human-sized servings of grapes a day. Currently, five to nine servings of fruits and vegetables are recommended as part of the DASH diet. 

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