The Nutrition Benefits of Grapes

Did you know that grapes are berries? Yep. And grapes share many of the same nutritional properties as blueberries, which includes the polyphenol resveratrol, but grapes contain even more vitamins A, C and the mineral iron than their blueberry cousins. Grapes also possess cardiovascular benefits that other fruits, including citrus fruits like oranges and grapefruits, do not. 

Grapes versus citrus fruits

According to a study published in The Journal of Nutrition, “Red wine and grapes contain polyphenolic compounds, including flavonoids, which can reduce platelet aggregation and have been associated with lower rates of cardiovascular disease. Citrus fruits contain different classes of polyphenolics that may not share the same properties.”1 The purpose of the study was to evaluate whether commercial grape, orange and grapefruit juice, when consumed daily, would reduce ex vivo platelet activity. Long story short, only the grape juice proved useful.

The researchers discovered that purple grape juice contained approximately three times the number of polyphenolics as the citrus juices, and acted as a potent platelet inhibitor in healthy subjects while orange and grapefruit juices showed no effect. The platelet inhibitory effect of the flavonoids in grape juice may decrease the risk of coronary thrombosis and myocardial infarction.

Grape flavonoids

No matter how similar two things may be, they can never be the same. In the case of grape flavonoids that's a good thing. All fruits and vegetables contain flavonoids, but those found in grapes seem to possess their own unique traits. This is why so many researchers have devoted time and grant money to discovering why grape flavonoids are different from other plant flavonoids. And, as it turns out, grape skin color dictates its flavonoid content.

The lighter the grape the less powerful the flavonoids they contains, the darker the grape the more powerful the flavonoids they contain. For example: red, purple and black grapes all contain resveratrol, but white and green grapes do not. Purple and black grapes contain quercetin, but the others do not. So, it's not just a richer flavor to be had by consuming darker grape varietals, they are simply healthier.

As it stands, purple grapes are the favorite among medical researchers. They are also the grape variety used to make standard grape juice. This is fortuitous as several studies have shown that purple grapes and their juice are highly beneficial to heart health. One example is a 1999 study, funded by the American Heart Association, which proved that “[s]hort-term ingestion of purple grape juice improves FMD [(flow-mediated vasodilation)] and reduces LDL susceptibility to oxidation in CAD [(coronary artery disease)] patients. Improved endothelium-dependent vasodilation and prevention of LDL oxidation are potential mechanisms by which flavonoids in purple grape products may prevent cardiovascular events, independent of alcohol content.”

Quercetin benefits

Quercetin isn't just a flavonoid, it's a powerful antioxidant. Multiple research studies have shown that quercetin's talent for scavenging damaging particles in the body make it an excellent protector of both DNA and tissue cells. Other studies have shown that quercetin has “antiviral, anti-inflammatory, antibacterial, and muscle-relaxing properties”3 as well.

Why resveratrol still matters

You may have heard of the recent studies that suggest resveratrol could be detrimental to men's health. If you haven't, I'll explain. According to the study, using resveratrol supplements negatively affected men, by offsetting the benefits of their cardiovascular exercise routines. This affect was only found in older men, however, but it's significant, as cardiovascular exercise is one of the most effective ways for seniors to prevent heart disease and its associated risks.

According to a study published in the Journal of Physiology, “Resveratrol administration also abolished the positive effects of exercise on low-density lipoprotein, total cholesterol/high-density lipoprotein ratio and triglyceride concentrations in blood (P < 0.05). Resveratrol did not alter the effect of exercise training on the atherosclerosis marker vascular cell adhesion molecule 1 (VCAM-1). Sirtuin 1 protein levels were not affected by resveratrol supplementation. These findings indicate that, whereas exercise training effectively improves several cardiovascular health parameters in aged men, concomitant resveratrol supplementation can blunt these effects.”4

However, there is no evidence to suggest that resveratrol intake from their source – FOOD – had any negative affects on men of any age. That's the takeaway here. Eating your nutrients is superior to swallowing them in pill form. Despite the hoopla, there is much to recommend resveratrol, regardless of one's gender, so long as you get the nutrient from grapes and other resveratrol-rich foods.

Resveratrol, in its natural form and in wine, has proven over several decades to be good for one's health, particularly the heart. But like most nutrients, it's most effective and less detrimental when it comes from foods. But even supplement studies have shown that resveratrol is effective for improving certain conditions. In the study 'Resveratrol: Cellular actions of a potent natural chemical that confers a diversity of health benefits', it was shown that resveratrol had positive effects on metabolism and could increase the lifespan of the various organisms tested. According to researchers, “Its effects arise from its capacity to interact with multiple molecular targets involved in diverse intracellular pathways. Most well known is the ability of resveratrol to activate sirtuins, a class of NAD+-dependent deacetylases that affect multiple transcription factors and other protein targets.”

One benefit of the resveratrol “scandal” is that it has shined a light on the importance of getting one's nutrients directly from their source instead of popping pills and hoping for the best. I do recognize that sometimes, for a variety of reasons, supplementing may be necessary; but, whenever feasible, you should get your nutrients from whole foods.


References

1 Keevil JG, Osman HE, et al. “Grape Juice, But Not Orange Juice or Grapefruit Juice, Inhibits Human Platelet Aggregation”. The Journal of Nutrition, January 1, 2000. Web. August 17, 2015

2 Stein JH, Keevil JG, et al. “Purple Grape Juice Improves Endothelial Function and Reduces the Susceptibility of LDL Cholesterol to Oxidation in Patients With Coronary Artery Disease”. The American Heart Association, March 9, 1999. Web. August 17, 2015

3 Jan AT, Kamli MR, et al. “Dietary Flavonoid Quercetin and Associated Health Benefits – An Overview”. Food Reviews International, volume 26, issue 3, 2010. Web. August 18, 2015

Corinna Underwood. “Black Grapes Vs Red Grapes”. Livestrong.com, February 18, 2015. Web. August 18, 2015

“Quercetin”, n.d. University of Maryland Medical Center. Web. August 18, 2015

4 Gliemann L, Schmidt JF, et al. “Resveratrol blunts the positive effects of exercise training on cardiovascular health in aged men”. The Journal of Physiology, October 15, 2013. Web. August 18, 2015

5 Marques FZ, Markus MA, Morris BJ. “Resveratrol: Cellular actions of a potent natural chemical that confers a diversity of health benefits”. The International Journal of Biochemistry & Cell Biology, November 2009. Web. August 20, 2015

A guest blog post by holistic writer Andrea Lewis.  Consult with your doctor before making any medical or health changes.