Grape Skin

Grape Skin

Grape skin is either red, green, or purplish-black in color. The outer layer of the grapes is actually a nutrient powerhouse, consisting of bioflavonoids, polyphenols, resveratrol and other health-promoting enzymes. Although the stem and seeds of the grapes are often used in making nutritional supplements, the extract sometimes contains grape skin only.

Benefits of Grape Skin

Grape skins have been used for centuries to treat numerous conditions and improve overall health. An overwhelming body of research supports the following health benefits of consuming grape skins:

Fights Cancer

Test tube studies have shown that grape skin extracts can inhibit the growth and reproduction of various types of cancer cells.^[1-3] According to these studies, the resveratrol in grape skin exhibits antioxidant properties which induce programmed cell death (apoptosis) in cancer cells and other malignant cells.

Maintains a Healthy Heart

Several studies have shown that consumption of grape skin and other grape products may have beneficial effect on the heart by improving blood circulation, decreasing cellular damage induced by free radicals, improving blood vessel function, normalizing blood lipids, and modulating inflammatory process.^[4-7]

Improves Memory and Brain Function

Consumption of flavonoids, specifically anthocyanins, from grapes may have a beneficial effect on brain function and central nervous system by inhibiting nerve cell inflammation and reducing oxidative stress.^[8] According to a study published in the British Journal of Nutrition, 12 weeks supplementation with grape skin extract in older adults with mild memory decline was associated with significant improvement in measures of verbal learning and spatial recall.^[9]

Lowers High Blood Pressure

Resveratrol and polyphenols in grape skin have been shown to exert blood pressure-lowering effects. One clinical trial revealed that the specific mechanism by which these substances exert this effect is by increasing the production of nitric oxide. This in turn causes relaxation of blood vessels, thereby improving blood circulation and lowering blood pressure.^[10]   

Improves Blood Sugar Levels

One study have shown that the resveratrol in grape skin appears to increase insulin sensitivity (body’s response to the effects of insulin) when supplemented in obese persons at 150 mg daily for 30 days.^[11] After the treatment, researchers found a significant reduction in blood sugar levels (4.2%). This blood sugar-lowering effect of resveratrol can help normalize blood sugar levels especially in diabetics.

Improves Body Composition

Test tube studies have shown that resveratrol from grape skin has anti-obesity properties.^[12-13] According to these studies, resveratrol has the ability to induce programmed cell death of fat cells and prevent conversion of muscle cells into fat cells.   

Improves Exercise Endurance

One study found that active adults who took 150 mg resveratrol from grape skin daily over the course of 4 weeks experienced an improvement in power output and exercise endurance compared to those who took placebo.^[14]

References:

1. Hudson TS, Hartle DK, Hursting SD, et al. Inhibition of prostate cancer growth by muscadine grape skin extract and resveratrol through distinct mechanisms. Cancer Res. 2007;67(17):8396-405.
2. Morré DM, Morré DJ. Anticancer activity of grape and grape skin extracts alone and combined with green tea infusions. Cancer Lett. 2006;238(2):202-9.
3. Burton LJ, Rivera M, Hawsawi O, et al. Muscadine Grape Skin Extract Induces an Unfolded Protein Response-Mediated Autophagy in Prostate Cancer Cells: A TMT-Based Quantitative Proteomic Analysis. PLoS ONE. 2016;11(10):e0164115.
4. Vislocky L.M., Fernandez M.L. Grapes and grape products: Their role in health. Nutr. Today. 2013;48:47–51. doi: 10.1097/NT.0b013e31823db374.
5. Li H., Förstermann U. Red wine and cardiovascular health. Circ. Res. 2012;111:959–961. doi: 10.1161/CIRCRESAHA.112.278705.
6. Nassiri-Asl M., Hosseinzadeh H. Review of the pharmacological effects of Vitis vinifera (grape) and its bioactive compounds. Phytother. Res. 2009;23:1197–1204. doi: 10.1002/ptr.2761.
7. Xia E.-Q., Deng G.-F., Guo Y.-J., Li H.-B. Biological activities of polyphenols from grapes. Int. J. Mol. Sci. 2010;11:622–646. doi: 10.3390/ijms11020622.
8. Tsuda T. Dietary anthocyanin-rich plants: Biochemical basis and recent progress in health benefits studies. Mol. Nutr. Food Res. 2012;56:159–170. doi: 10.1002/mnfr.201100526.
9. Krikorian R., Nash T.A., Shidler M.D., Shukitt-Hale B., Joseph J.A. Concord grape juice supplementation improves memory function in older adults with mild cognitive impairment. Br. J. Nutr. 2010;103:730–734. doi: 10.1017/S0007114509992364.
10. Chiva-blanch G, Urpi-sarda M, Ros E, et al. Dealcoholized red wine decreases systolic and diastolic blood pressure and increases plasma nitric oxide: short communication. Circ Res. 2012;111(8):1065-8.
11. Timmers S, et al. Calorie restriction-like effects of 30 days of resveratrol supplementation on energy metabolism and metabolic profile in obese humans. Cell Metab. (2011).
12. Umek RM, Friedman AD, McKnight SL CCAAT-enhancer binding protein: a component of a differentiation switch. Science. (1991).
13. Rayalam S, et al. Resveratrol induces apoptosis and inhibits adipogenesis in 3T3-L1 adipocytes . Phytother Res. (2008).
14. Scribbans TD1, et al Resveratrol supplementation does not augment performance adaptations or fibre-type-specific responses to high-intensity interval training in humans . Appl Physiol Nutr Metab. (2014).