Many wine drinkers -- and, in the last year, beer chuggers -- have justified their consumption of these libations on the grounds that they're therapeutic, cutting the risk of heart attacks. Well, teetotalers, here's your comeback: Tell them that they can derive much of the same artery-clearing benefit from plain grape juice.
Indeed, a daily glass of concord grape juice may offer more protection against formation of the undesired blood clots than aspirin does, a new study indicates.
For the past several years, John D. Folts, director of the Coronary Artery Thrombosis Research and Prevention Laboratory at the University of Wisconsin-Madison Medical School, has been investigating the clot-inhibiting activity of a number of common drinks -- initially to probe possible mechanisms of the French paradox.
That paradox goes something like this: French cuisine is renowned for its extensive reliance on butter, bacon, lard, and other animal products rich in artery-clogging fats. As a result, the French tend to develop fairly high concentrations of cholesterol in their blood, a risk factor for atherosclerosis. The long-standing conundrum is why the French don't also experience high rates of heart disease -- comparable to those in other populations with similarly elevated cholesterol.
In mulling over what makes the French different, many researchers have focused on that nation's love affair with and high consumption of wine. What attribute in wine might offer heart benefits?
Though Folts and others have shown that plain alcohol is somewhat protective, they found that for inhibiting blood clots, wine is more potent than pure alcohol. He now suspects that flavonoids, natural antioxidant pigments found in many plants, account for wine's enhanced effect.
The anti-stick factor
Platelets, a class of blood cells, aid in clotting. They keep a fresh cut in the skin from causing life-threatening blood loss. In persons with coronary artery disease, however, overly sensitive platelets may foster clots that obstruct blood flow through vessels already narrowed by fatty deposits. The result can be a heart attack.
In a host of studies, Folts' team has shown that red wine and dark beers inhibit platelets in the blood from becoming unusually sticky and generating those risky, clot-forming clumps. Indeed, these dark-colored drinks clearly outperform lighter ones, such as vodka, white wine, and pale lagers.
What tends to distinguish a dark beer from a light brew, or a ruby-hued wine from a white one, is their concentrations of quercetin, rutin, resveratrol, and other flavonoid pigments.
In their new study, the Wisconsin scientists initially recruited five healthy men and women (including Folts) to drink about three servings of purple grape juice at a sitting -- some 20 to 24 ounces. An hour later, the researchers sampled the volunteers' blood and put it into a device that measures platelet stickiness. Compared to blood samples taken an hour prior to drinking the juice, the later blood was almost 50 percent less prone to platelet clumping.
That's a lot of juice, Folts acknowledges, so he decided to explore what would happen if he halved the dose and drank it daily for a week. Two or 3 days after the last glass was drunk, each volunteer returned for another blood test.
The results, reported this week, indicate that regular consumption of the popular juice appears to have a carryover effect. Even after a hiatus of several days, the volunteers' blood was about 25 percent less likely to clump than before the treatment began.
This finding was particularly welcome, Folts notes, because most heart attacks occur in the early morning, sometimes just as an individual is getting up. His group's data now suggest that even if the juice had been drunk the day before, it would still confer some protection.
Last year, Folts reported data from dogs indicating that dark beer was especially effective at inhibiting platelet activation (see "A couple of heart-friendly brews"). In a new study with dogs, he finds that grape juice is every bit as potent as the Guinness extra stout he tested last year.
The citrus difference
Together, living plants manufacture some 1,000 different flavonoids. Though grape is far from the only juice to provide a rich source of these colored compounds, the others don't necessarily contain therapeutic doses of the flavonoids responsible for inhibiting platelet clumping. To test this idea, Folts' group had the volunteers repeat the week-long experiment, this time drinking equivalent amounts of orange or grapefruit juice daily.
As expected, Folts told Science News Online, their new study showed that when it comes to holding down platelet clumping, "the orange and grapefruit juice had no effect at all."
That's no reason to eschew these citrus drinks, however. Research under way at the University of Western Ontario's Centre for Human Nutrition finds that, at least in the test-tube, a number of citrus-derived flavonoids slow the growth of breast cancer cells. Their preliminary findings indicate that some of these flavonoids -- alone or in fruit juice -- significantly augment the activity of certain anticancer drugs (see Juicy Anticancer Prospects).
For nearly a decade, cardiologists have known that healthy men over 50 -- and postmenopausal women -- can nearly halve their risk of heart attack by taking an aspirin every other day. Like grape juice, this drug appears to work by inhibiting platelet aggregation.
However, when adrenaline is pumped into the blood in response to stress or heavy exercise, Folts points out, aspirin's platelet inhibition virtually disappears. So in the new study, he tested grape juice drinkers' blood to see if the same thing happened to them.
In one case, he took the volunteers' blood, added adrenaline to it, and then measured its susceptibility to platelet clumping. In another, some volunteers exercised and then provided blood for analysis. In both cases, Folts says, the juice depressed platelet clumping.
Although he considers the juice's contrast to aspirin especially exciting, he cautions that these data "are preliminary, and it would be premature and irresponsible to make broad recommendations from them." In particular, he notes, aspirin users should continue taking the drug. Indeed, it's possible that grape juice may augment any benefits normally derived from aspirin, he says.
His team plans to begin a study of people with coronary artery disease to compare platelet clumping susceptibility in those taking aspirin alone or paired with the juice.
While grape juice sounds like pretty benign therapy, Folts cautions that it may pose problems for persons with diabetes. A 12-ounce glass contains 60 grams of natural sugarsalmost twice as much as in a regular cola drink. However, he notes, there is a sugarfree alternative. One of his earlier studies showed that drinking 2 cups of tea -- also rich in flavonoids -- daily will offer the same benefits.
Folts' work, supported in part by Welch Foods, Inc. (maker of Welch's Grape Juice), was reported on March 18 at the American College of Cardiology annual meeting in Anaheim, Calif.
Cowen, R. 1989. Aspirin and heart disease: A final report. Science News 136(July 22):55.
Csatari, J. 1995. A drink to your health. Men's Health. 10 (July-August):33.
Demrow, H.S., P.R. Slane, and J.D. Folts. 1995. Administration of wine and grape juice inhibits in vivo platelet activity and thrombosis in stenosed canine coronary arteries. Circulation 91(Feb. 15):1182
Edwards, D.D. 1988. Aspirin cuts risk of first heart attack. Science News 133(Jan. 30):68.
Fackelmann, K.A. 1993. Rich foods, clotting, and heart attacks. Science News 143(Jan. 30):77.
___. 1991. A heartening finding for women on aspirin. Science News 140(July 27):55.
Raloff, J. 1997. Versatile cancer weapon in grapes. Science News Online, Feb. 8.
___. 1996. A couple of heart-friendly dark brews. Science News 149(May 4):287.
___. 1996. Juicy anticancer prospects. Science News 149(May 4):287.
___. 1996. Have Danes solved the French paradox? Science News. 149 (March 30):197.
___. 1995. New support for tea's heart-y benefits. Science News. 148(Dec. 9):399.
___. 1993. Add tea to that old 'apple a day' adage. Science News. 144(Oct. 30):278.
Seachrist, L. 1995. Wine, beer, liquor benefit the heart. 148(Dec. 2):380.
1993. New clue to morning heart risk. Science News 143(April 10):239.
1992. Grape juice vs. wine: A healthy debate. Science News 142(July 18):47.
1991. Prime-time clot-busting. Science News 140(Nov. 23):334
1987. Safe supinity. Science News 131(June 27):409.
Sources:John D. Folts
This week's Food for Thought is prepared by Janet Raloff, senior editor of Science News.
Illustration: Wendy Temple.