According to researchers at the University of Wisconsin School of Medicine, patients with narrowing of the coronary arteries who drank purple grape juice daily for eight weeks showed significant improvement in their arterial function, reports BW Healthwire.
The researchers also found that purple grape juice is effective independently of vitamin E, and at quantities lower than previously tested.
The study is published in the September issue of The American Journal of Cardiology. It looked at the effect of drinking purple grape juice on flow mediated vaso-dilation, a measurement of the ability of the artery to relax and expand to accommodate increased blood flow. This represents a good gauge for measuring general arterial health, and the arteries of patients with vascular coronary disease typically do not relax well.
18 men and four women with severely compromised arterial function drank purple grape juice over an eight-week span. Half the participants consumed about 21 ounces of juice, depending on body weight. The others consumed half that dose, on average about ten ounces of juice a day. At the end of eight weeks, both groups showed a similar response: roughly doubling their flow mediated dilation (from 1.3 per cent to 2.9 per cent).
"It is interesting to see that the response to juice was approximately the same at both the higher and lower doses," notes James H. Stein, M.D., Assistant Professor of Medicine and senior author of the study. "The previous work we have done has been at slightly higher dosing levels. Now we are seeing that patients with severe vascular disease are responding to smaller quantities of juice, doses averaging ten ounces per day, depending on body weight."
As part of the study design, vitamin E supplementation (400 IU) was included in the subjects' diet after four weeks. The study found that the effects of the juice were independent of the presence of vitamin E.
While a previous study reported a larger increase in flow-mediated dilation, the researchers point to several factors contributing to this study's results.
First, participants in this study had, on average, more severe arterial disease.
Second, juice in this study was stored in a manner that may have adversely affected its potency.
Third, study subjects, because of the severity of their disease, were typically taking statins, beta-blockers or calcium channel blockers, common prescriptions drugs which may also, according to the researchers, have had a mediating effect on some of the findings reported in the study.
Researchers also found that after eight weeks of juice consumption, increases in lipid levels and triglycerides were not significant. Changes in insulin and glucose levels were also not statistically significant.