Emerging Research

Grapes and Healthy Aging

 

Family Brunch with GrapesEmerging research suggests that grapes, as part of a healthy diet and lifestyle, may contribute to health.  The studies below look at the variety of ways in which grapes may play a role in maintaining certain aspects of health that can decline as we age.

The promising study results provided here will contribute to future research in these areas.

In each of the studies cited below, the researchers used a whole grape powder made from whole fresh grapes – a mix of red, green and black varieties – that were ground and freeze-dried.  Using the grape powder allows for year-round study of grapes by researchers.  The whole grape powder is a substitute for fresh grapes.

Eye Health

Regular consumption of a grape-enriched diet helped protect the retina from damage in three laboratory models of age-related macular degeneration. 1 2 3

In the first study, adding grapes to the diet early in life prevented blindness in animals prone to developing retinal damage in old age. The grape-enriched diet protected against oxidative damage to the retina by protecting the function of its retinal epithelium pigment cells. This study showed that consuming grapes at an early age protected vision into old age.

In another animal model of macular degeneration, a grape-enriched diet preserved retinal function in multiple ways, from countering oxidative stress, to lowering inflammatory proteins and increasing protective proteins in the retina.

In a third study, supplementing the diet with grapes helped reduce damaging and undesirable blood vessel formation in the choroid layer of the eye that can leak into the retina and lead to vision loss.

 

1. Yu, C.C., Nandrot, E.F., Dun, Y., & Finnemann, S.C. (2012).  Dietary antioxidants prevent age-related retinal pigment epithelium actin damage and blindness in mice lacking ?v?5 integrin. Free Radical Biology and Medicine, 52(3), 660-70. doi: 10.1016/j.freeradbiomed.2011.11.021

2. Patel, A.K., Davis, A., Rodriguez, M.E., Agron, S., & Hackam, A.S. (2016).  Protective effects of a grape-supplemented diet in a mouse model of retinal degeneration. Nutrition, 32: 384-390.

3. Kanavi, M.R., Darjatmoko, S., Wang, S., Azari, A.A., Farnoodian, M., Kenealey, J.D., …Polans, A.S. (2014).  The sustained delivery of resveratrol or a defined grape powder inhibits new blood vessel formation in a mouse model of choroidal neovascularization. Molecules, 19, 17578-17603.

Brain Health

A grape-enriched diet protected against metabolic brain decline in Alzheimer’s-related areas of the brain.4

In a pilot study of people with early memory decline, subjects were either fed whole grape powder equivalent to just 2 ¼ cups of grapes per day – or a placebo powder.  The results showed that consuming grapes preserved healthy metabolic activity in regions of the brain associated with early Alzheimer’s disease, where metabolic decline takes hold.  Subjects who didn’t consume grapes exhibited significant metabolic decline in these critical regions.  Additionally, those consuming the grape-enriched diet showed beneficial changes in regional brain metabolism that correlated to improvements in cognition and working memory performance.

 

Grape consumption helped protect brain neurons from oxidative damage and cell death, and decreased inflammation.5

In this study, animals were fed a control diet or a grape-enriched diet at one of two levels:  low and high amounts of grapes.  Both grape diets helped protect against neuronal damage caused by loss of oxygen in the brain.  Animals not receiving a grape-enriched diet had extensive damage.  Grapes also reduced inflammation in the support cells to the neurons.

 

A grape-supplemented diet helped protect against oxidative stress-induced anxiety, memory impairment and associated high blood pressure.6,7

This animal study investigated the role of oxidative stress in the combined occurrence of anxiety, cognitive impairment and hypertension, using a model of oxidative stress.  The grape-fed animals exhibited a reduction in anxiety-like behavior, no increase in blood pressure or memory impairment, which the researchers attributed to the antioxidant capacity/activity of the grape polyphenols.

A second, and similar study by the same research team investigated the role of diminished estrogen influence at menopause and its association with oxidative stress and resulting cognitive decline, heightened anxiety and hypertension.  The control animals had increased blood pressure, anxiety-like behavior and learning memory impairment.  They exhibited increased oxidative stress in the brain, serum and urine, and lower amounts of an antioxidant enzyme in the brain.  Those consuming the grape-enriched diet reversed these effects.

 

Adding grapes to the diet helped protect against cognitive, behavioral and biochemical impairments related to traumatic stress.8

A third study looked at the effects of a grape-enriched diet on post-traumatic stress in animals.  In this study, the animals consuming grape powder reversed the behavioral and memory problems that were observed in those not receiving a grape-enriched diet.  The researchers attributed these benefits to both gene activation and enhanced antioxidant activity resulting from grape intake.

 

4. Lee, J.K., Torosyan, N., & Silverman, D.H. (2017).  Examining the impact of grape consumption on brain metabolism and cognitive function in patients with mild decline in cognition: A double-blinded placebo controlled pilot study. Experimental Gerontology, 87 (Pt A), 121-128.

 5. Wang, Q., Simonyi, A., Li, W., Sisk, B.A., Miller, R.L., MacDonald, R.S., …Sun, A.Y. (2005).  Dietary grape supplement ameliorates cerebral ischemia-induced neuronal death in gerbils. Molecular Nutrition and Food Research, 49, 443-451.

6. Allam F., Dao, A.T., Ghugh, G., Bohat, R., Jafri, F., Patki, G., …Salim, S. (2013, June).  Grape powder supplementation prevents oxidative stress-induced anxiety-like behavior, memory impairment, and high blood pressure in rats.  Journal of Nutrition, 143(6), 835-842. doi: 10.3945/jn.113.174649

7. Patki, G., Allam, F.H., Atrooz, F., Dao, A.T., Solanki, N., Chugh, G., … Salim, S. (2013, September).  Grape powder intake prevents ovariectomy-induced anxiety-like behavior, memory impairment and high blood pressure in female Wistar rats.  PLoS ONE, 8(9), e74522. doi: 10.1371/journal.pone.0074522

8. Solanki, N., Alkadhi, I., Atrooz, F., Patki, G., & Salim, S. (2015, January).  Grape powder prevents cognitive, behavioral and biochemical impairments in a rat model of post-traumatic stress disorder.  Journal of Nutrition Research, 35(1), 65-75. doi: 10.1016/j.nutres.2014.11.008

Bladder Health

A grape-enriched diet helped protect bladder function against oxidative damage caused by obstruction to the bladder. 9 10 11

Obstructive bladder dysfunction, such as that observed with prostate enlargement, is linked to oxidative damage of the nerves, synapses and smooth muscle cells within the bladder wall.  A series of animal studies investigated the impact of adding grapes to the diet on bladder function.  The studies showed that grapes provided an antioxidant effect that helped to prevent and delay the damaging effects of oxygen deprivation (ischemia) and free radicals to cells that result from a partial obstruction to the bladder.  Grapes helped maintain membrane and mitochondrial function in the cells, and reduce and reverse bladder damage caused by a partial outlet obstruction.  The beneficial effects were attributed to the combination of multiple active components in grapes — not just one.

 

9. Agartan, C.A., Whitbeck, C., Sokol, R., Chichester, P., & Levin, R.M. (2004). Protection of urinary bladder function by grape suspension. Phytotherapy Research, 18, 1013-18. doi: 1002/ptr.1620

10. Lin, A.Y., Mannikarottu, A., Chaudhry, A., Whitbeck, C., Kogan, B.A., Chichester, P., & Levin, R.M. (2005, December). Protective effects of grape suspension on in vivo ischemia/reperfusion of the rabbit bladder. British Journal of Urology International, 96, 1397-402. doi: 10.1111/j.1464-410X.2005.05832.x

11. Venugopal, V., Leggett, R.E., Shuler, C., & Levin, R.M. (2010, November-December). Effect of hydrogen peroxide on rabbit urinary bladder citrate synthase activity in the presence and absence of a grape suspension. International Brazilian Journal of Urology, 36(6):749–758.

Gastrointestinal Health

Consuming grapes helped counter the adverse effects of a high saturated fat diet and promote improvements in gut bacteria and intestinal health. 12, 13

In one study, animals consuming a high saturated fat diet that was supplemented with grapes (3% or 5% of the diet) exhibited reductions in overall and subcutaneous body fat that were positively associated with beneficial changes in intestinal bacteria and health; e.g., increases in some beneficial bacteria, decreases in some less desirable bacteria, increased microbial diversity, and improved gut barrier function.

In a second study, consuming grape polyphenols in addition to a high-fat diet reduced the percentage of body fat, including subcutaneous and visceral fat deposits; reduced markers of inflammation; improved glucose tolerance and intestinal barrier function.

 

12. Baldwin, J., Collins, B., Wolf, P.G., Martinez, K., Shen, W., Chuang, C.C., …McIntosh, M.K. (2016).  Table grape consumption reduces adiposity and markers of hepatic lipogenesis and alters gut microbiota in butter fat-fed mice. Journal of Nutritional Biochemistry, 27, 123-135.

13. Collins, B., Hoffman, J., Martinez, K., Grace, M., Lila, M.A., Cockrell, C., …McIntosh, M.K. (2016).  A polyphenol-rich fraction obtained from table grapes decreases adiposity, insulin resistance and markers of inflammation and impacts gut microbiota in high-fat-fed mice. Journal of Nutritional Biochemistry, 31, 150-165.

Liver Health

Grape extract helped promote the healthy functioning of liver cells, and protected liver cells from oxidative stress and cell death.14

Preventing liver cell death (apoptosis) may lead to the prevention of various liver diseases, and cell mitochondria are pivotal in controlling cell life and death.

In this cell study, grape extract helped promote liver cell viability, growth and metabolic activity.  Specifically, grapes positively influenced a critical cell communication pathway that regulates liver cell health.  Additionally, grapes helped protect the cells against oxidative stress and mitochondrial injury.

 

14. Xu, Y., Khaoustov, V.I., Wang, H., Yu, J., Tabassam, F., & Yoffe, B. (2009).  Freeze-dried grape powder attenuates mitochondria- and oxidative stress-mediated apoptosis in liver cells. Journal of Agricultural and Food Chemistry, 57:9324-9331.  doi: 10.1021/jf900851n

Cell Inflammation

Grape extract helped to reduce inflammation and insulin resistance mediated by both immune cells and fat cells, and preserved cell function.15

In a cell study of immune and fat cells, grapes were shown to reduce inflammation and insulin resistance (improved glucose uptake) by fat cells, thus helping to protect important cell functions.  Obesity and type 2 diabetes are both linked to chronic inflammation in fat tissue.

 

A grape-enriched diet improved glucose tolerance and reduced markers of inflammation without affecting body fat levels in obese animals.16

This study looked at the anti-inflammatory properties of grape powder and grape powder extract as well as their impact on glucose tolerance in high fat fed obese animals.  The grape powder diet improved glucose tolerance at 5 weeks but not beyond, and decreased markers of inflammation in both serum and adipose tissue at 18 weeks.  Quercetin showed anti-inflammatory effects on human fat cells. The grape extract had no impact on glucose tolerance at any time point.

 

15. Overman, A., Bumrungpert, A., Kennedy, A., Martinez, K., Chuang, C.C., West, T., …McIntosh, M.K. (2010, January).  Polyphenol-rich grape powder extract (GPE) attenuates inflammation in human macrophages and in human adipocytes exposed to macrophage-conditioned media. International Journal of Obesity, .  doi: 10.1038/ijo.2009.296

16. Chuang, C.C., Shen, W., Chen, H., Xie, G., Jia, W., Chung, S., & McIntosh, M.K. (2012).  Differential effects of grape powder and its extract on glucose tolerance and chronic inflammation in high-fat-fed obese mice.  Journal of Agricultural and Food Chemistry, 60, 12458-12468.

Diabetes

Grape consumption helped reduce the onset of autoimmune diabetes in animals.17

In this study, a grape-enriched diet protected against the destruction of insulin-producing cells in the pancreas, reduced levels of inflammation in the spleen, and increased antioxidant capacity in non-obese, diabetic animals.

 

17. Zunino, S.J., Storms, D.H., & Stephensen, C.B. (2007).  Diets rich in polyphenols and vitamin A inhibit the development of Type 1 autoimmune diabetes in nonobese diabetic mice. Journal of Nutrition,  137, 1216-1221.

Bone Health

A grape-enriched diet increased bone calcium retention and cortical bone properties in an animal model for menopause.18

In this study, the animals consuming the grape-enriched diet had increased bone calcium retention and cortical bone properties – specifically greater thickness and breaking strength – than those without grapes in their diet.

 

18. Hohman, E.E., & Weaver,M. (2015). A grape-enriched diet increases bone calcium retention and cortical bone properties in ovariectomized rats. Journal of Nutrition, 145(2), 253-9. doi: 10.3945/jn.114.198598

Cell Health

Grape consumption helped protect healthy colon tissue by inhibiting a key cell communication pathway that promotes colon cancer cell growth.19

In a human study of five colon cancer patients, researchers studied the effects of consuming grapes on colon tissue.  After the subjects consumed whole grape powder for two weeks, samples of healthy and cancerous tissue were taken from each subject’s colon.  The results showed a 47% reduction in the expression of the target genes responsible for promoting tumor growth in the colon, compared to baseline measurements before the study.  The beneficial effects were observed in the healthy tissue of the cancer patients, but not the cancerous tissue, suggesting that regular consumption of grapes may help to maintain a healthy colon.

Grape extract demonstrated anti-cancer activity alone, but was more potent in combination with green tea.20

In an animal study, tumor growth was stimulated with a specific cancer-growth protein, and the impact of grapes and green tea was tested. Researchers found that a whole grape extract had some effect, but a grape skin extract combined with green tea was more effective.  Green tea on its own provided no impact.

Additionally, cell studies compared the ability of various grape extracts to inhibit the growth protein in human cervical cells and animal mammary cells.  Grapes and green tea combined were more effective than either alone.  Grape skin extracts were more effective than whole grape extract or a grape juice extract.  This study also observed that grape polyphenols (specifically flavonoids) inhibited the growth protein without impacting healthy cells.

 

The role of grapes in maintaining cell health to prevent the development of cancer is an area of ongoing scientific interest, with promising preliminary work in the areas of breast, prostate and colon cancers.21

 

19. Nguyen, A.V., Marinez, M., Stamos, M.J., Moyer, M.P., Planutis, K., Hope, C., & Holcombe, R.F. (2009). Results of a phase I pilot clinical trial examining the effect of plant-derived resveratrol and grape powder on Wnt pathway target gene expression in colonic mucosa and colon cancer. Journal of Cancer Management and Research, 1, 25-37.

20 Morré, D.M., & Morré D.J. (2006, July).  Anticancer activity of grape and grape skin extracts alone and combined with green tea infusions. Cancer Letters, 18, 238(2), 202-9.   doi: 10.1016/j.canlet.2005.07.011

21. Vislocky, L.M., & Fernandez, M. (2010). Biomedical effects of grape products. Nutrition Reviews. Vol. 68(11), 656-670.  doi: 10.1111/j.1753-4887.2010.00335.x

decorative section divider

ABOUT California TABLE GRAPES

Californians have been cultivating grapes for more than two centuries. Today, 99 percent of U.S. table grapes are produced in California's warm, dry climate that is ideal for grape growing. With more than 85 grape varieties grown, California grapes come in three colors—green, red and black—and are in season from May through January.