Grape health benefit Information, juice content of resveratrol and nutritional composition
October 27 2015 by Ray Sahelian, M.D.

Grapes are one of the most valued conventional fruits, worldwide. The flesh of grapes may be just as heart healthy as the skin. Does this mean that white wine offers as good cardiovascular protection as red wine? Researchers prepared grape skin and grape flesh extracts from four varieties of red grape and tested their cardioprotective effects in rats. They found that the flesh extract was just as protective as the skin extract. The skin of red grapes is a rich source of anthocyanins, potent antioxidants that contribute to the red color of the fruit. Red grapes are usually crushed whole, meaning the anthocyanins are transferred to resulting wine and juice. To make most white wine or white grape juices however the skins are separated from the flesh. That situation led to the conventional belief that red wines and red grape juice are healthier for the heart than white. It's possible that the antioxidant potential of skin and flesh of grapes are comparable with each other despite of the fact that flesh does not possess any anthocyanin activities. While grape skin has anthocyanin concentrations of about 128 milligrams per 100 grams, the flesh contains no such compounds. However, the radical scavenging abilities of both the flesh and skin extracts appear to be the same. The flesh of grapes contain polyphenols, but not of the anthocyanin type. Significant concentrations of caffeic acid, caftaric acid, and coutaric acid have been reported. Such compounds are also present in white grape varieties. Several organic acids and polyphenols possessing potent antioxidant activities present in the flesh of grapes are also found in white wines.
   Grapes have a very important compound called resveratrol which has shown anti-aging benefit in rodent studies.

Cancer and tumor prevention
Asian Pac J Cancer Prevention. 2014. Effect of grape procyanidins on tumor angiogenesis in liver cancer xenograft models. In recent years a wide variety of flavonoids or polyphenolic substances have been reported to possess substantial anti-carcinogenic and antimutagenic activities. Grape proanthocyanidins (GPC) are considered as good examples for which there is evidence of potential roles as anti-carcinogenic agents. Methods: A xenograft model was established using H22 cells subcutaneously injected into mice and used to assess different concentrations of grape proanthocyanidins (GPC) and Endostar. Treatments were maintained for 10 days, then levels of vascular endothelial growth factor (VEGF) and microvessel density (MVD) were examined by immunohistochemistry, while VEGF mRNA was determined by real-time PCR in tumor tissue. Results: The expression of MVD and VEGF decreased gradually as the concentration of GPC increased.There was a significant positive correlation between MVD and VEGF. Conclusions: These results suggest that GPC restrains the growth of tumor, possibly by inhibiting tumour angiogenesis.

Grape juice benefit for heart
Grape juice seems to have the same protective effect against heart disease as red wine does. Researchers at the Universite Louis Pasteur de Strasbourg examined the effect on the heart of Concord grape juice. Dr. Valerie Schini-Kerth and her team found that polyphenols in Concord grape juice activate endothelial cells to produce nitric oxide, which helps to protect against cardiovascular disease and to maintain healthy blood vessels and blood pressure.
Red wine and certain types of grape juice have high levels of polyphenols, which block the production of a protein linked to cardiovascular disease -- the number one killer in many Western countries. Heart and vascular problems develop when endothelial cells that make up blood vessels do not work properly. Polyphenols work the same way in red wine and in grape juice. The amount of polyphenols in grape juice, as in red wine, depends on the type of grape used and how it is processed. This research was partly funded by Welch Foods Inc., a leading producer of grape juice.

2009 - E. Mitchell Seymour, at Michigan State University, studied the effect of regular table grapes -- a blend of green, red, and black grapes -- that were mixed into the rat diet in a powdered form, as part of either a high- or low-salt diet. Comparisons were made between rats consuming the grape powder and rats that received a mild dose of the common blood pressure drug hydrazine. After 18 weeks, the rats that received the grape-enriched diet powder had lower blood pressure, better heart function and fewer signs of heart muscle damage than rats that ate the same salty diet but didn't receive grapes. Rats that received the blood pressure medicine, hydrazine, along with a salty diet also had lower blood pressure, but their hearts were not protected from damage as they were in the grape-fed group. The study was presented at the 2009 Experimental Biology convention in New Orleans.

Grape Juice Benefit in kidney patients
Concentrated red grape juice exerts antioxidant, hypolipidemic, and antiinflammatory effects in both hemodialysis patients and healthy subjects.
Am J Clin Nutrition. 2006. Servicio de Bioquimica-Investigacion, Hospital Ramon y Cajal, Madrid, Spain.
Patients treated with hemodialysis frequently experience cardiovascular complications attributed, among other causes, to dyslipidemia, increased oxidative stress, and inflammation. The aim of the study was to study the effects of dietary supplementation with concentrated red grape juice, a source of polyphenols, on lipoprotein profile, antioxidant capacity, LDL oxidation, and inflammatory biomarkers. Twenty-six patients receiving hemodialysis and 15 healthy subjects were instructed to drink 100 mL concentrated red grape juice /d for 14 d. Blood was drawn at baseline, twice during concentrated red grape juice supplementation, and twice during the 6-mo follow-up period. As a control, 12 other randomly recruited hemodialysis patients not receiving concentrated red grape juice were studied. Lipids, apolipoproteins, oxidized LDL, and antioxidant vitamins were measured in plasma. The bioavailability of concentrated red grape juice polyphenols was assessed in healthy subjects. RESULTS: The maximum plasma concentration of quercetin was achieved 3 h after concentrated red grape juice ingestion, which indicates that supplement-derived polyphenols are rapidly absorbed. In both healthy subjects and hemodialysis patients, concentrated red grape juice consumption increased the antioxidant capacity of plasma without affecting concentrations of uric acid or ascorbic acid; reduced the concentration of oxidized LDL; and increased the concentration of cholesterol-standardized alpha-tocopherol. concentrated red grape juice supplementation also caused a significant decrease in LDL-cholesterol and apolipoprotein B-100 concentrations, while increasing the concentrations of HDL cholesterol and apolipoprotein A-I. In a further study in hemodialysis patients, concentrated red grape juice supplementation for 3 wk significantly reduced plasma monocyte chemoattractant protein 1, an inflammatory biomarker associated with cardiovascular disease risk. Dietary supplementation with concentrated concentrated red grape juice improves the lipoprotein profile, reduces plasma concentrations of inflammatory biomarkers and oxidized LDL, and may favor a reduction in cardiovascular disease risk.

Diabetes
Type 2 Diabetes and Glycemic Response to Grapes or Grape Products.
J Nutr. 2009. USDA, Agricultural Research Service, Western Human Nutrition Research Center, University of California, Davis, CA 95616.
Type 2 diabetes affects approximately 7% of the population in the United States and is characterized by decreased disposal of glucose in peripheral tissues due to insulin resistance and overproduction of glucose by the liver, defects in pancreatic beta-cell function, and decreased beta-cell mass. Obesity, decreased physical exercise, and consumption of foods with a high glycemic index (GI) and load are major predisposing factors in the development of type 2 diabetes. The GI is used to evaluate the rise in blood glucose levels in response to food. The GI provides an indication of the quality of carbohydrate in a food. The glycemic load (GL) is used to provide information about the quantity of carbohydrates in a food and the insulin demand. Individuals with diabetes are advised to maintain a diet of low-GL foods, because low-GL diets improve diabetes symptoms. Grapes have a mean GI and GL in the low range. Little research has been performed with grapes and/or grape products to determine the glycemic response either alone or with a meal. Grapes and other fruits contain numerous polyphenols, including the stilbene resveratrol, the flavanol quercetin, catechins, and anthocyanins that have shown potential for reducing hyperglycemia, improving beta-cell function, and protecting against beta-cell loss. Therefore, with a low mean GI and GL, grapes or grape products may provide health benefits to type 2 diabetics.

Grape Research studies
Although most of the parts of the grapevine are useful, primarily, the grape is considered as a source of unique natural products not only for the development of valuable medicines against a number of diseases, but also for manufacturing various industrial products. Over the last few decades, apart from the chemistry of grape compounds, considerable progress has been made towards exploring the biological activities of various grape-derived constituents. Today, it is well established that in addition to serving as food, the grape is a major source of several phytonutrients. The main biologically active and well-characterized constituent from the grape is resveratrol, which is known for various medicinal properties in human diseases.

Comparison of Cardioprotective Abilities between the Flesh and Skin of Grapes.
J Agric Food Chem. 2006. Department of Medical Pharmacology, Chemotherapy and Toxicology, Faculty of Medicine, University of Milan, Milan, Italy; C.R.A., I.V.T.P.A. (Institute of Technological Development of Agricultural Products), Milan, Italy; C.R.A., I.S.E. (Enology Experimental Institute), Velletri, Italy; C.N.R. (National Council of Research), Institute of Molecular Science and Technology, Milan, Italy; and Cardiovascular Research Center, University of Connecticut School of Medicine, Farmington, Connecticut 06030.
Recent studies have documented that grapes and grape juices are equally cardioprotective as red wine. The existing reports implicate that the skin and seeds of the grapes containing polyphenolic antioxidants are instrumental for the cardioprotective properties of grapes. The present study examines if the flesh of grapes also possesses any cardioprotective abilities. Three groups of randomly selected rats were fed, water only (control), flesh of the grapes (2.5 mg/kg b. wt.) or the skins (2.5 mg/kg b. wt.) for 30 days. The results indicate for the first time that the flesh of grapes are equally cardioprotective as skin, and antioxidant potential of skin and flesh of grapes are comparable with each other despite of the fact that flesh does not possess any anthocyanin activities.

questions
Q. I am very interested in doing the Grape Cure for Cancer. It involves a 12 hour water fast followed by a 12 hour grape fast for six weeks. No other food in consumed. Because of the resveratrol it is supposed to be very effective in the process of cancer. I would very much like to hear your opinion.
   A. We have no experience with such a grape cure for cancer fast. There are potential dangers to fasting.