"Concord grape juice might help promote healthy, wide arteries," claims Larry King, Cable News Network talk show host, in a radio ad for Welch’s 100 Percent Grape Juice. "And healthy arteries get more blood to your body when and where you need it." The 30-second ad attributes the finding to "a small preliminary study" by the American Heart Association. Can drinking purple grape juice really help your arteries?

It seems to be true: Studies funded in part by Welch Foods, including one published by the AHA, show Concord grape juice’s potentially heart-protective effects. But you’ve got to drink a lot of juice to reap the benefits described.

In the study cited in Welch’s ad, reported in the Sept. 7, 1999, AHA journal Circulation, researchers at the University of Wisconsin asked 15 adults who had coronary-artery disease to drink an average of 24 ounces of grape juice a day. After two weeks, the juice nearly tripled the ability of the arteries to widen, thereby boosting blood flow. The scientists attributed those effects to the juice’s high level of flavonoids, substances that help the arteries relax and constrict normally. The flavonoids are also antioxidants that make "bad" LDL cholesterol significantly less susceptible to oxidation--and thus less likely to damage the artery walls and restrict blood flow.

In a more recent study, funded partly by Welch Foods and published in December 2002 in the American Journal of Clinical Nutrition, 15 healthy adults were asked to drink roughly the same amount of juice, that is, 24 ounces a day for two weeks. Tests of the juice-drinkers’ blood showed that both LDL cholesterol and plasma proteins--which may also damage the arteries when oxidized--became less prone to oxidation. A control group that took vitamin E, another antioxidant, exhibited similar benefits for LDL, but not for plasma proteins.

Those grape findings fit well with the larger body of evidence on red wine’s heart-protective effects. Wine contains antioxidants from grapes too, though its alcohol may play a larger role in protecting the arteries of light-to-moderate drinkers.

Drinking lots of purple grape juice, unlike overindulging in alcohol, won’t directly cause medical problems. However, the juice is loaded with sugar--40 grams per cup, compared with about 22 grams in orange juice and 27 grams in Coca-Cola. Indeed, the three daily cups of grape juice consumed in the studies contained more than 500 calories. So the juice is not a good choice for those watching their weight. Some people may want to dilute it with water, seltzer, or other juices if that makes it more palatable to them. In theory, you’d probably reap at least some of the benefits of the juice if you drank less than three cups a day.