Drinking purple grape juice contributes to healthy cardiovascular function in at least two related ways, according to Georgetown University researchers in the most recent issue of the medical journal Circulation... Their study showed that drinking grape fruit juice has a direct effect on important biological functions like blood clotting. It also appears to increase plasma levels of important antioxidants while decreasing production of a key free radical in the body.

"We have already seen that drinking purple grape juice has potentially beneficial effects. This study gives us a better understanding of the mechanisms behind those effects," explains Jane E. Freedman, M.D., assistant professor of medicine and pharmacology at Georgetown University and the lead author of the study.

"What we are seeing for the first time is that the flavonoids in purple grape juice work in two related pathways: Firstly, they have a protective effect on antioxidants, allowing them to provide active protection against oxidative stress for longer periods. Second, they also seem to have a direct, positive effect on a number of biological functions like platelet activity, nitric oxide production and signaling in cells, all of which may be protective factors."

In the study, 20 subjects drank about two cups of juice a day for 14 days. The actual dose was based on body weight, so the average female consumed less juice. After that, the levels of vitamin # (alpha-tocopherol) in their blood was about 13% higher than at the beginning of the study. Additionally, the total antioxidant capacity of their plasma increased by 50%, nitric oxide production from platelets increased by 70%, and platelet activity significantly decreased.

In contrast, the study also found that production of superoxide, a potentially harmful free radical, was reduced by a third after supplementation with grape juice. These results were consistent with the initial in vitro test results performed on blood samples drawn from the healthy subjects.

After the study, Dr Freedman stated, "The antioxidant protective effect we see in the grape juice is new information that, when added to what we already knew about grape juice's other benefits, helps us better understand the mechanisms by which grape juice works in the body."

Healthy production of nitric oxide fights atherosclerosis in several ways. The researchers felt that the higher levels of antioxidants may help preserve the nitric oxide in the body, increasing its beneficial effects.

"It's likely that the protective effects of the purple grape juice are due to the juice's flavonoids," adds Dr. Freedman. "But interestingly enough, the study found that when individual groups of flavonoids were separated, from the juice and tested in isolation, not all of them had the same effect as that of the whole juice."