Grape Polyphenols Reduce Metabolic Syndrome Risk Factors

With all of the attention surrounding diabetes these days, you’ve probably heard of a condition called metabolic syndrome—a collection of risk factors that are linked to type 2 diabetes, cardiovascular disease and stroke. These risk factors include high blood pressure, high triglycerides, low HDL (“good”) cholesterol, raised fasting glucose levels and a waist circumference measurement of 35 inches or more (think “beer gut”). If you have three of these five risk factors, then you may have metabolic syndrome, which puts you at increased risk of more serious complications.

Insulin resistance is the cornerstone of metabolic syndrome. Your pancreas produces the hormone insulin, which is necessary for the absorption and utilization of sugar in your diet. However, when you have insulin resistance, your body doesn’t respond as accurately to insulin, which causes the pancreas to produce more insulin.

This is where the merry-go-round starts, because the more insulin you have in the bloodstream, the greater your risk for type 2 diabetes.

Along with insulin resistance, endothelial dysfunction is a hallmark of metabolic syndrome. Endothelial dysfunction is characterized by narrowed blood vessels, inflammation and pro-thrombotic properties. In fact, it is one of the first signs of atherosclerosis and impending cardiovascular disease.

Fortunately, research has shown that certain antioxidants can have a protective effect on the endothelium by stimulating the formation of nitric oxide (NO), a compound critical for healthy cardiovascular function. Produced by the endothelium, NO plays a huge role in the creation of a substance called cyclic guanosine monophosphate (cGMP), which prevents clotting and promotes healthy dilation of veins and arteries. When the endothelial lining becomes damaged, NO production suffers, making all the blood vessels susceptible to inflammation, clotting and other negative effects.

While there’s little doubt that antioxidants play an important part in protecting the heart, a team of researchers recently examined the effect of one particular type of antioxidant—grape polyphenols—on the reduction of metabolic syndrome risk factors, especially the cardiovascular ones.

Grapes contain numerous antioxidant polyphenols—anthocyanins, flavonols and resveratrol, to name a few. Resveratrol, in particular, has been shown to be extremely heart healthy by reducing LDL cholesterol and inflammation.3-4 As many wine lovers know, red wine is high in resveratrol, and when consumed in moderation (one to two glasses per day), has some impressive heart-protective properties.

Researchers chose to examine grape polyphenols in relation to metabolic syndrome because few studies had been done to evaluate their beneficial effects on this condition and its cardiovascular risk factors.

They followed 25 men (ages 30 to70) who had metabolic syndrome. The men were divided into two groups—those who took grape polyphenol powder (46 g/day), and those who took a placebo powder. After 30 days of consuming their respective powders, participants underwent a three-week washout period, and then were assigned the alternative treatment for another 30 days. During the duration of the study, researchers asked the participants to abstain from consuming other polyphenol-rich foods, including tea, berries, grapes and wine.
The results of the study showed that the grape polyphenols significantly improved vascular endothelial function and NO availability, while also reducing certain risk factors associated with metabolic syndrome.

Specifically, the participants had a lower resting systolic (top number) blood pressure reading after the grape polyphenol period (122+/- 11 mmHg) versus the placebo period (128+/- 10 mmHg). A difference of 6 mmHg may not seem dramatic, but according to researchers, the U.S. National High Blood Pressure Education program estimates that a 5 mmHg reduction of systolic blood pressure could result in a 14 percent overall reduction in mortality from stroke and a nine percent reduction in mortality from cardiovascular disease.

In addition, the inflammatory marker plasma sICAM-1 concentrations were lower after consumption of the grape polyphenols compared with placebo.

Go for the Grape

Because metabolic syndrome has so many different factors, no simple pharmaceutical solutions exist to treat it. The best solution doctors can offer is to adjust certain lifestyle factors like diet and exercise. This, of course, is sound advice.

Everyone should be eating a clean diet and exercising anyway, but those with metabolic syndrome could see dramatic changes in their condition with these two changes alone. However, considering the proven health benefits of grape polyphenols, it’s great news indeed that this nutrient can now be added to your arsenal in the war against metabolic syndrome and its health effects.

A good way to make grape polyphenols a part of your daily regimen—particularly if you have metabolic syndrome or if you are at risk of developing cardiovascular disease—is to simply make red grapes a regular part of your diet. Eat them as is, or add them to salads and smoothies. And, as mentioned earlier, red wine is a good option to boost your polyphenol intake. Just be sure not to overindulge—drink no more than one or two glasses a day.

However, to achieve real therapeutic benefit, you may want to think about taking grape polyphenols in supplement form. Fortunately, polyphenols like resveratrol and grape seed extract are readily available at most health food stores and vitamin retailers.

References:
Schini-Kerth VB et al. Pflugers Arch. 2010;459:853-62.
Barona J, et al. J Nutr. 2012 Sep;142(9):1626-32.
Zern TL and Fernandez ML. J Nutr. 2005 Oct;135(10):2291-4.
Xia EQ, et al. In J Mol Sci. 2010 Feb 4;11(2):622-46.