Grapes: Rich in Polyphenols

 

In recent years, grapes have gained scientific validation as a top-notch defender against cardiovascular disease, cancer, and age-related cognitive decline.¹

The benefits associated with grape consumption are related to its unique and diverse composition of antioxidants called polyphenols. The skin of the grape is a rich source of the cancer-fighting compound resveratrol and its seeds are heavily concentrated in proanthocyanidins, which possess 50 times more antioxidant power than vitamin C.² In addition, the vibrant color of grapes, grape juice, and red wine reflects dense amounts of anthocyanins. A study in the Journal of Agricultural and Food Chemistry revealed that grape juice has the third highest antioxidant potency out of twelve tested antioxidant beverages.³

Fighting Cardiovascular Disease

 

Grape and its products combat atherosclerosis and cardiovascular disease through multiple mechanisms including modulating oxidative stress, stimulating endothelial and platelet derived nitric oxide, inhibiting LDL oxidation, and lowering blood pressure.

While free radicals are a normal byproduct of metabolism, an excess of these unstable molecules can produce oxidative stress that induces damage and dysfunction of the endothelium (inner lining of blood vessels), one of the early events of atherosclerosis.⁴ Grape polyphenols can effectively combat free radicals, in turn lowering oxidative stress and endothelial dysfunction. In one study, pre- and post- menopausal women consuming 36 grams of grape powder (corresponds to 1.5 cups of fresh grapes) per day for four weeks had significantly reduced levels of F2-isoprostanes, a marker of oxidative stress.⁵

One of the ways oxidative stress causes endothelial dysfunction is by interfering with the production or activity of nitric oxide, one of the essential protective factors released by the endothelium.⁶ This molecule signals the smooth muscle cells in the artery wall to relax and dilate, thereby increasing optimal blood flow. In the laboratory, treatment of endothelial cells that line the arteries of the heart with grape juice activated the enzyme nitric oxide synthase, resulting in the generation of nitric oxide.⁷

In addition to its role in arterial dilation, nitric oxide also possesses strong anti-inflammatory and platelet inhibitory properties. The latter benefit was reported in the journal Circulation as human volunteers consuming grape juice for two weeks experienced a 71% increase in nitric oxide release from platelet cells, suppressing platelet “stickiness” responsible for thrombosis and heart attacks. This beneficial effect was attributed to a 35% reduction in superoxide radicals, which enhanced nitric oxide availability.⁸

Even in people with a high degree of endothelial dysfunction, grape juice shows promise in improving blood vessel health. Patients with heart disease ingesting grape juice for 14 days recorded nearly a 3-fold increase in the flow-mediated vasodilation of the brachial artery, an indicator of endothelial function, compared to baseline.⁹

It’s well-established that LDL oxidation is a key initiator of early atherosclerosis. Oxidized LDL cholesterol is more readily attracted into the arterial wall, triggering a cascade of events that stimulates inflammation and eventually the formation of atherosclerotic lesions. In a study published in the American Journal of Clinical Nutrition, scientists found that healthy subjects drinking grape juice daily for two weeks reduced their rate of LDL oxidation by 9%.¹⁰

Several studies have documented the efficacy of grapes to lower high blood pressure. A University of Connecticut study showed that 46 grams of grape powder (equivalent to 2 servings of fresh grapes) per day for 30 days improved endothelial function and nitric oxide availability in participants with metabolic syndrome, leading to a reduction in mean systolic blood pressure of 6 mmHg and mean diastolic blood pressure of 9 mmHg compared to a placebo.¹¹ In a second study involving hypertensive men, ingesting grape juice daily for eight weeks dropped systolic blood pressure by an average 7 mmHg and diastolic pressure by 6 mmHg.¹²

Selecting and Storing Grapes¹

1. Grapes are available all-year round, but growing season is from July to December.
2. Choose fully ripe grapes that are firm and plump.
3. Grapes should be firmly attached to the stem, wrinkle free, and not leaking juice.
4. Store in a container or plastic bag in the refrigerator for up to 5 days to retain freshness

 

 

Protecting Against Cancer

 

Mounting evidence indicates that grapes are front-line fighters against cancer. At the cellular level, grape antioxidants neutralize free radicals that damage DNA and produce mutations that transform healthy cells into cancerous ones. This was demonstrated in an 8-week study as healthy subjects ingesting 16 ounces of grape juice daily increased their plasma antioxidant activity and reduced free radical levels by 15%. This resulted in a 21% reduction in lymphocyte DNA damage.¹³

After lung cancer, breast cancer is the leading cause of cancer mortality among women.¹⁴ An in vitro study using extract from grapes inhibited breast cancer cell growth by up to 72% and enhanced apoptosis (cell death) by up to 33%.¹⁵ This effective combination might be the reason for the results of an epidemiological study that revealed that women with the highest grape consumption were 34% less likely to develop breast cancer compared to those with the lowest intakes.¹⁶

Grape seed extract might also protect against prostate cancer, the most common cancer among men.¹⁷ In a study published in Nutrition and Cancer, researchers studied the relationship between long-term dietary supplement use and prostate cancer in more than 32,000 men aged 50 to 76. Compared to non-users, those who supplemented with grape seed extract slashed their risk of prostate cancer by 41%.¹⁸

Tumor cells rely on the formation of new blood vessels (angiogenesis) for nourishment and growth. Colon cancer cells treated with grape seed proanthocyanidins in the laboratory showed inhibition of the vascular endothelial growth factor (VEGF) and angiopoietin 1 (Ang1), thereby blocking blood supply to tumor cells.¹⁹

The tendency for pancreatic cancer to invade adjacent tissues and spread to other organs in the body makes it one of the deadliest cancers. Grape seed proanthocyanidins were shown to reduce the invasion potential of pancreatic cancer cells by beneficially altering the gene expression of matrix metalloproteases, according to a study reported in the journal Pancreas.²⁰

Improving Cognitive Function

Grape juice’s ability to reduce oxidative stress in the brain might enhance memory and improve cognition with aging, according to a study published in the British Journal of Nutrition. Older adults supplemented with grape juice daily for 16 weeks showed a significant improvement on verbal memory tests, whereas the placebo group showed no improvement.²¹

Summary

Grapes and their products possess a wealth of anthocyanins and proanthocyanidins that have been shown to provide top-notch protection against cardiovascular disease, cancer, and age-related cognitive decline.

If you have any questions on the scientific content of this article, please call a Life Extension® Wellness Specialist at 1-866-864-3027.

References

1. Available at: http://www.whfoods.com/genpage.php?tname=foodspice&dbid=40. Accessed November 24, 2012.
2. Shi J, Yu J, Pohorly JE, Kakuda Y. Polyphenolics in grape seeds-biochemistry and functionality. J Med Food. 2003Winter; 6(4):291-9.
3. Seeram NP, Aviram M, Zhang Y, et al. Comparison of antioxidant potency of commonly consumed polyphenol-rich beverages in the United States. J Agric Food Chem. 2008 Feb; 56(4):1415-22.
4. Higashi Y, Noma K, Yoshizumi M, Kihara Y. Endothelial function and oxidative stress in cardiovascular disease. Circ J. 2009 Mar;73(3): 411-8.
5. Zern TL, Wood RJ, Greene C, et al. Grape polyphenols exert a cardioprotective in pre-and postmenopausal women by lowering plasma lipids and reducing oxidative stress. J Nutr. 2005 Aug;135(8): 1911-7.
6. Tousoulis D, Kampoli AM, Tentolouris C, et al. The role of nitric oxide on endothelial function. Curr Vasc Pharmacol. 2012 Jan;10(1): 4-18.
7. Anselm E, Chataigneau M, Ndiaye M, Chataigneau T, Schini-Kerth VB. Grape juice causes endothelium-dependent relaxation via a redox-sensitive Src-and Akt-dependent activation of eNOS. Cardiovasc Res.2007 Jan;73(2): 404-413.
8. Freedman JE, Parker C 3rd, Li L, et al. Select flavonoids and whole juice from purple grapes inhibit platelet function and enhance nitric oxide release. Circulation. 2001 Jun;103(23): 2792-8.
9. Stein JH, Keevil JG, Wiebe DA, Aeschlimann S, Folts JD. Purple grape juice improves endothelial function and reduces the susceptibility of LDL cholesterol to oxidation in patients with coronary artery disease. Circulation. 1999 Sep;100(10): 1050-5.
10. O’Byrne DJ, Devaraj S, Grundy SM, Jialal I. Comparison of the antioxidant effects of Concord grape juice flavonoids alpha-tocopherol on markers of oxidative stress in healthy adults. Am J Clin Nutr. 2002 Dec;76(6): 1367-74.
11. Barona J, Aristizabal JC, Blesso CN, Volek JS, Fernandez ML. Grape polyphenols reduce blood pressure and increases flow-mediated vasodilation in men with metabolic syndrome. J Nutr. 2012 Sept;142(9):1626-32.
12. Park YK, Kim JS, Kang MH. Concord grape juice supplementation reduces blood pressure in Korean hypertensive men: double-blind, placebo controlled intervention trial. Biofactors. 2004;22(1-4):145-7.
13. Park YK, Park E, Kim JS, Kang MH. Daily grape juice consumption reduces oxidative DNA damage and plasma free radicals in healthy Koreans. Mutat Res. 2003 Aug;529(1-2):77-86.
14. Available at: http://www.cdc.gov/cancer/dcpc/data/women.htm. Accessed November 24, 2012.
15. Sharmma G, Tyagi AK, Singh RP, Chan DC, Agarwal R. Synergistic anti-cancer effects of grape seed extract and conventional cytotoxic agent doxorubicin against human breast carcinoma cells. Breast Cancer Res Treat. 2004 May;85(1):1-12.
16. Do MH, Lee SS, Jung PJ, Lee MH. Intake of fruits, vegetables, and soy foods in relation to breast cancer risk in women: a case-control study. Nutr Cancer. 2007;57(1):20-7.
17. Available at: http://www.cdc.gov/cancer/prostate. Accessed November 24, 2012.
18. Brasky TM, Kristal AR, Navarro SL, et al. Specialty supplements and prostate cancer risk in the VITamins and Lifestyle (VITAL) cohort. Nutr Cancer. 2011;63(4):573-82.
19. Huang S, Yang N, Liu Y, et al. Grape seed proanthocyanidins inhibit colon cancer-induced angiogenesis through suppressing the expression of VEGF and Ang1. Int J Mol Med. 2012 Dec;30(6):1410-6.
20. Chung YC, Huang CC, Chen CH, et al. Grape-seed procyanidins inhibit the in vitro growth and invasion of pancreatic carcinoma cells. Pancreas. 2012 Apr;41(3):447-54.
21. Krikorian R, Nash TA, Shidler MD, Shukitt-Hale B, Joseph JA. Concord grape juice supplementation improves memory function in older adults with mild cognitive impairment. Br J Nutr. 2010 Mar;103(5):730-4.