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Grapes: Defenders Against Diabetes, Heart Disease and Cancer

Posted May 21 2010 12:19am

Eating grapes may well slow what for a large number of American's is a downhill spiral of high blood pressure and insulin resistance eventually leading to heart disease and type 2 diabetes. Scientists at the University of Michigan Health System are learning clues to the effect of grapes in reducing risk factors related to cardiovascular disease and metabolic syndrome. The effect is thought to be due to phytochemicals - naturally occurring antioxidants - contained within grapes. Grapes are naturally occurring and have been cultivated for thousands of years by humans.   They come in a wide array of varieties. [1,2,3]

Researchers studied the effect of regular table grapes (a blend of green, red and black grapes) that were mixed into powdered form and incorporated into the diets of laboratory rats as part of a typical high-fat, American style diet. All the rats used were from a research breed prone to being overweight. Many factors were compared between the rats consuming a grape-enriched diet and the control rats receiving no grape powder. Researchers added calories and sugars to the control group to balance the extra calories and sugars gained from getting the grape powder. After three months, the rats in the grape-enriched diet group had lower blood pressure, better heart function, and reduced indicators of inflammation in the heart and the blood than rats who received no grape powder. These subjects also had lower triglycerides and improved glucose tolerance. The effects were seen even though the grape-fed animals had no change in body weight. [1,4]

The study also looked for signs of inflammation, oxidative damage and other molecular indicators of cardiac stress. Again, the rats who consumed the grape powder had lower levels of these markers than rats who did not receive grapes. There is no agreed upon method to diagnose metabolic syndrome.   Metabolic syndrome is a cluster of characteristics: excess belly fat (for men, a waist measuring 40 inches or more and for women, a waist measuring 35 inches or more); high triglycerides which can lead to plague build-up in the artery walls; high blood pressure; reduced glucose tolerance; and elevated c-reactive protein, a marker for inflammation in the body. Those with metabolic syndrome are at higher risk for cardiovascular disease and type 2 diabetes. [1,4]

Interestingly, the commonly discussed "French Paradox" may well be the observed clinical model that has preceded scientific analysis. This refers to the observation that the French are known to drink red wine and eat foods high in fat content (notably butter, pork, foie gras and the like).   Research seems to indicate that moderate intake (no more than 2-3 glasses) of wine may have a protective effect against the potential ill effects of certain foods. [5]

Medical Properties

Phytochemicals are thought to play a role in helping to mediate the effects of fat, sugar and excess calories in the diet.   Known phytochemicals include phenolic acids, flavonols, flavon-3-ols, myricetin, peonidin, flavonoids, resveratrol, quercetin, tannins, anthocyanins, kaempferol, cyanidin, ellagic acid and proanthocyanidins. The various substances are thought to hold a number of medicinal properties. Red grapes and red wine contain levels of flavonoids which have antioxidant properties and help to reduce the risk for cancer and heart disease. These flavonoids also have an anti-inflammatory and anti-allergic effect. Red grape leaves have been traditionally used to treat diarrhea, heavy menstrual bleeding and uterine hemorrhage. [6]

Heart disease

A number of studies have shown that moderate consumption of red wine has cardioprotective properties and can decrease coronary heart disease mortality. Studies have shown that quercetin and other polyphenols in wine prevent oxidation.One study has shown that red wine protects low density lipoproteins from oxidation. The flavonoids ellagic acid and resveratrol have been shown to reduce the risk of coronary heart disease. Grape seed proanthocyanidins may have therapeutic potential in the prevention and treatment of vascular complications in diabetic patients. [6,7]


Grape contains phenolic compounds, including resveratrol, flavon-3-ols, caffeic acid, ellagic acid and quercetin. Phenolic compounds are known to have anticancer properties.   They have been associated with inhibition of various cancers, including colon, esophagus, lung, liver, mammary and skin cancers. Resveratrol can inhibit cancer formation in different ways. Resveratrol stops DNA damage, improves DNA repair, slows down tumor growth and slows cell transformation from normal to cancerous. One study has demonstrated that resveratrol has cancer chemopreventive activity in different stages of carcinogenesis. Resveratrol was found to act as an antioxidant and antimutagen and to induce phase II drug-metabolizing enzymes; it mediated anti-inflammatory effects and inhibited cyclooxygenase and hydroperoxidase functions. Not only red grape juice but grape seeds are rich in anticancer phytochemicals. [6,7,8,9]

Antioxidant activity

Grape phenolics such as catechins, flavonols, anthocyanins and tannins have strong antioxidant activity and help to prevent oxidative damage. Grape antioxidants help to prevent the risk of several chronic and age related diseases including dementia, cancer, heart disease and cataracts. [6,7,8,9]

Antibacterial and antiviral activity

A study by Pisha et al, entitled "Fruits and vegetables containing compounds that demonstrate pharmacological activity in humans" and published in Economic and Medicinal Plant Research (1994, 6:189-233), showed that grape phenolics possess antibacterial and antiviral activities. The following phytochemicals in grape have weak antibacterial activity: hydroxybenzoic acid, salicylic acid, gallic acid and protocatechuic acid. Chlorogenic acid and epicatechin have shown antiviral activity against some viruses. [6]

So it would appear that the grape, in it's domestic form of red, white and black table grapes, as well as it's more exalted form in red wine, offers a number of health benefits for us.   Research will continue into the various substances which contribute to these benefits, but in the meantime, we can enjoy some grapes and cheese with a glass or two of red wine.

[1] Grapes Reduce Risk Factors for Heart Disease and Diabetes, Animal Study Shows -

[2] Grape -

[3] List of grape varieties -

[4] Regular Grape Intake Reduces Cardiac and Renal Dysfunction and Metabolic Syndrome in Obesity-Prone Rats - FASEB J. 2010 24:219.2 (Meeting Abstract) - Federation of American Societies for Experimental Biology

[5] The French Paradox and Beyond: Living Longer with Wine and The Mediterranean Lifestyle -

[6] Phytochemicals - Phytochemicals

[7] Inhibition in vitro of oxidation of human low density lipoproteins by phenolic compounds in wine - Lancet (1993, 39:1743-1748)

[8] Cancer Chemopreventive Activity of Resveratrol, a Natural Product Derived from Grapes - Science 10 January 1997: Vol. 275. no. 5297, pp. 218 - 220

[9] Antioxidants and Cancer Prevention: Fact Sheet - National Cancer Institute -



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