(April 2001)
Grape juice fights arterial disease - that was the headline of the Reuters dispatch referring to an article in the journal Circulation.
Grapes, like nuts, seeds, some vegetables and fruits, contain flavonoids - interesting substances that are also found in red wine and act as antioxidants. The investigators studied twelve men and three women, average age 62 years, who had known coronary heart disease. They were asked to drink Welch's 100% Concord Grapes for fourteen days - about 21 ounces or two-thirds of a quart a day. Studies were then made of the diameter of an artery in the arm and the ability of low-density lipoprotein cholesterol (LDL, so called bad cholesterol) to be oxidized, a step thought to be important for LDL to get into blood vessel walls and cause arteriosclerosis.
The results showed that, after the grape juice diet, the blood vessels showed a greater ability to dilate and the LDL was more resistant to oxidation, both reactions likely to reduce the risk of coronary heart disease and heart attacks.
Commentary: This is a good preliminary study. But, that is all it is; whether findings in the arm can really be directly related to blood vessels of the heart is not clear.
The authors of this study point out that the beneficial effects of red wine may not be related to the alcohol, but rather the flavonoids in the grapes used to make the red wine. The flavonoids are a complex group of chemicals with different, but often overlapping, functions. Their names are not exactly household words - querecetin (a very active antioxidant), myricetin, catechin (a powerful inhibitor of LDL oxidation), kaempferol, tannic acid. Of course, it is also true that the reported beneficial effects found in this study may be due to substances in grapes other than flavonoids.
Alcohol, in particular red wines, appears to be beneficial in reducing heart attack risk. That benefit has been ascribed primarily to raising blood levels of protective high density lipoprotein cholesterol (HDL-good cholesterol) and diminished clotting tendencies of the blood that can be the precipitating event for a heart attack.
In this study, the grape juice did not increase the HDL levels.
The interference with LDL oxidation does appear to be an important factor in reducing the likelihood of developing arteriosclerosis, but this has not yet been definitely proven.
We still do not know for sure that flavonoids really do reduce coronary artery disease and heart attack risk, but they well may to a moderate extent. It could well be that grape juice could do as well as red wine, but this has to be documented in carefully controlled studies. That would be nice for those who are not wine drinkers, and it would avoid the risk for regular alcohol drinkers of losing control and becoming alcoholics. But, many questions remain including:
- Is grape juice really effective in reducing heart attack risk? That question is far different from showing that the grape juice can help dilate blood vessels and reduce LDL oxidation.
- What would be the effective grape juice dosage?
- Would drinking grape juice plus a glass or two of red wine a day give additional benefit?
- Are the beneficial effects really due to the flavonoids in grapes?
- Should grape juice or other flavonoids be part of your diet? The answer to that question is that fruits and vegetables should be a prominent part of the diet. Taken together, they reduce the risk of some cancers and also appear to reduce the risk of heart attack and stroke to a modest extent. Many fruits and vegetables contain flavonoids, but they also contain many other potential health-promoting substances. So, including grapes or grape juice as part of the fruits and vegetables in your diet is perfectly reasonable. Their apparent beneficial effect in health promotion may or may not have anything to do with their flavonoid content.
Grapes also have a constituent called resveretrol that may have beneficial effects against both cancer and heart disease. Here, again, much more study is required before we can have any definitive evidence on which to make a recommendation.
See the following table for flavonoid-containing foods.
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28 FOODS AND BEVERAGES WITH SUBSTANTIAL FLAVONOID ANTIOXIDANT ACTIVITY | ||
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apples |
cantaloupes |
oranges |
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apricots |
cereal grains (wheat, oats, barley) |
peaches |
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bananas |
endive |
pears |
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berries (including blueberries, gooseberries, blackberries, raspberries) |
garlic |
peanuts |
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broccoli |
grapefruit (whole fruit or juices) |
plums |
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brussels sprouts |
grapes |
potatoes (white and sweet) |
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cabbage |
kale |
red wine |
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leek |
rhubarb | |
|
lettuce |
tangerines | |
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onions |
tea (black) | |
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tomatoes | ||
Also, many spices and herbs -including coriander, mustard, parsley, peppers, rose hips, sage, and thyme
Stein, J.H., et al. Purple grape juice improves endothelial function and reduces the
susceptibility of LDL cholesterol to oxidation in patients with coronary artery disease. Circulation. Vol 100. (September 7) Pgs 1050-1055. 1999.
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