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.
The U-M team notes that a clinical research on grapes may be a possibility in the future, but is not currently planned.
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.
The rats in the study were from a strain called Dahl rats, which have been specially bred to all be susceptible to salt-induced hypertension. This allowed the researchers to look at a uniform sample of rats that would be affected in the same way by their diet, so that the effects of the salt level, grape powder and hydrazine could be seen clearly.
Each group of 12 rats was fed the same weight of food each day, with powdered grapes making up 3 percent of
|Contact: Kara Gavin|
University of Michigan Health System