Drink to Good Health: Resveratrol

This polyphenol (a type of plant compound) is an antioxidant that is naturally produced by several plants to provide protection from bacteria and pathogens. Red wine particularly has been touted as an excellent source of resveratrol, however the compound can also be found in blueberries, cocoa powder, cranberries, lingonberries, mulberries, peanuts, pistachios, purple grapes, red grapes, and in the roots of the Japanese knotweed plant.

The highest concentrations of the compound are found on the skin of red grapes making red wine highest in resveratrol. The amount of time the grape skin is fermented impacts the amount of resveratrol within the wine. White wine has less of the compound due to the skin of the grapes being removed earlier. Other factors including grape variety, humidity, and other environmental conditions also impact resveratrol content and the amount can range greatly from year to year. Most red wines contain anywhere between 0.2 to 12.59 mg/L of the compound. Typically organic wines are thought to have higher amounts due to less chemical usage and their need to produce more resveratrol to combat fungus. Pinot noir is fermented the longest with the skin intact which could also increase resveatrol levels. Wines from cooler regions such as Italian sangiovese, Australian shiraz, and French burgundy were found to have higher levels compared to warmer climates such as California, Spain, and South American wines.  

Resveratrol was discovered in 1939 but it was not until 1992 when scientists suggested resveratrol may be the reason for the heart benefits of red wine. The hypothesis was based on the “French Paradox” where high levels of saturated fat intake, smoking, and regular red wine consumption in France resulted in relatively low levels of mortality from coronary heart diseases. This suggested regular red wine consumption may provide protection from heart disease.  

Following the 1992 study, hundreds of reports have promoted the health benefits of resveratrol. The majority of studies have been conducted in test tubes or with animals. Several have been conducted on humans but these were not long term studies and have not shown significant evidence of resveratrols health benefits. Mouse studies have indicated activation of one gene that helps protect the body against side effects of obesity and diseases of aging. It is thought resveratrol may prevent heart disease by reducing inflammation, preventing the oxidation of LDL cholesterol, and preventing platelets from sticking together and forming clots. It is believes resveratrol may prevent cancer by reducing the spread of cancer cells. For Alzheimer’s disease resveratrol may protect nerves from damage. Resveratrol may also help prevent against insulin resistance, a precursor to diabetes.

Moderate alcohol consumption has been shown to reduce heart disease risk by 20-30%. Some studies have shown wine drinkers to have lower risks than people consuming beer or liquor; however other studies found no difference. It is not yet clear if polyphenols, such as resveratrol, in red wine have the most beneficial impact on reducing heart disease risk. Due to the limited studies in humans we are unable to confirm health benefits of resveratrol at this time.

Manufacturers have capitalized on selling resveratrol as a supplement, and while it is generally considered safe, the long term side effects have not been studied. Resveratrol does have estrogen like properties, similar to soy, and should not be taken by pregnant or breastfeeding women. It is also recommended children and adolescents under 18 not take the supplement as the effects on development are unknown. People on certain medications such as anticoagulents (Warfarin), antiplatelet drugs (Plavix, Persantine), and NSAIDs (aspirin, ibuprofen) are also advised not to take resveratrol supplements. Until more is known regarding the estrogen like properties of resveratrol, women at risk or with a history of estrogen-sensitive cancers should also avoid supplements.

In addition to resveratrol, red wine contains other polyphenol compounds and anthocyanins which have beneficial antioxidant properties. Until more research ensures the efficacy and safety of supplements my opinion is to consume these compounds from natural sources so they can work together in synergy with other phytochemicals.