What Are Polyphenols?

Polyphenols are a type of natural chemical in plants. They are part of a wider group of compounds, called antioxidants, that work to prevent cellular damage in the body. Unlike vitamins and minerals, polyphenols are not essential for human nutrition; however, evidence is mounting that these compounds play a significant role in achieving optimal health and preventing disease.

Identification

Polyphenols are found in all plants to varying degrees. They are responsible for much of the color, flavor, and scent in fruits, vegetables, seeds, legumes and grains. Brightly colored fruits, like berries, grapes, apples and pomegranates, as well as tea, cocoa and red wine, are especially high in these compounds. Polyphenols are found in highest concentrations in the peel or skin. They help make the plant hardy, protecting it from harmful bacteria and fungi, insects and ultraviolet light. They also are important for attracting pollinators.

Types

To date, more than 4,000 types of polyphenols have been identified in nature. They can be classified into two broad categories: flavonoids and nonflavonoids. Flavonoids include anthocyanins, a pigment in brightly colored fruit, catechins, abundant in cocoa and tea, and flavanones, found primarily in citrus fruits. The major nonflavonoids are ellagic acid, found in berries, nuts, and pomegranate, and coumarins, a mild toxin that occurs in certain legumes and grasses.

Effects

In humans, polyphenols act as antioxidants, helping to eliminate free radicals from the body. Free radicals are volatile molecules that damage cells, causing them to age. The name for this process is oxidative stress. Polyphenols and other antioxidants slow the rate of oxidative stress by stabilizing free radical molecules, turning them into harmless waste byproducts.

Benefits

A number of studies indicate that this reduction in oxidative stress can lower the risk of developing degenerative diseases. A South Korean study published in the March 2008 "Journal of Food Science" shows that a diet high in polyphenol-rich fruit cuts the odds of developing neurodegenerative disorders like Alzheimer's disease. In addition, a French study released in the November 2007 "FASEB Journal" indicates that high doses of polyphenolic compounds from red wine are beneficial in preventing cancer. At low doses the French researchers found that these same compounds were helpful in preventing and treating ischemic heart disease.

Considerations

The simple way to reap the benefits of polyphenols is to eat more fruits and vegetables. In recent years a number of supplements have hit the market that provide large doses of highly concentrated polyphenols. Resveratrol, a polyphenol found in grape skins and red wine, is often taken in supplemental form for its purported life-extension benefits. More research is needed to determine whether taking polyphenols in supplemental form provide the same benefits as consuming them in foods.

Resources

• Agricultural Research Service