The findings are reported in a letter to the editor of the November edition of Arteriosclerosis, Thrombosis, and Vascular Biology.
The study was conducted by researchers including Jane Freedman, MD, associate professor of medicine and pharmacology at Boston University's medical school and was partially funded by an unrestricted grant from grape juice maker Welch's.
The participants were assigned to drink either purple Concord grape juice or a placebo beverage for 14 days. Afterward, they abstained from both drinks for 14 days. Finally, they repeated the test using whichever drink they hadn't already tried.
"Good" HDL levels "significantly increased" in participants when they drank grape juice, write the researchers.
Grape juice drinkers had HDL levels of 50 mg/dL, compared with almost 45 mg/dL in the placebo group. An HDL level below 40 mg/dL is considered a risk factor for heart disease.
Soluble CD40 ligand is thought to contribute to the development of atherosclerosis and vascular inflammation, says Freedman in a news release.
Other indicators of inflammation weren't affected, probably because patients were already taking aspirin to fight inflammation.
The results suggest that alcohol-free grape juice might provide some of the cardiovascular benefits seen in studies of wine.
"There has been great interest in the possible benefits of drinking red wine for people with cardiovascular disease. But it has been offset, to a certain extent, by concerns about promoting alcohol consumption," says Freedman in the news release. This has led to the exploration of non- alcoholic grape products.
This is the first study to show its positive effect on CD40 ligand, an emerging indicator of heart disease, even in people already on aspirin.