Polyphenols are plant chemicals that work as antioxidants to protect the cells in your body from free radical damage. There are three major groups: carotenoids, which are related to vitamin A; allyl sulfides in garlic and onions; and the largest group, the polyphenols, which are found in many different foods.
Polyphenols all have similar ring-shaped chemical structures, and they can be categorized into four different groups based on the number of rings and the molecules that are attached to those rings. The groups are called phenolic acids, flavonoids, stilbenes and lignans.
Flavonoids work as both antioxidants and anti-inflammatory agents. There are several different types of flavonoids: flavones, flavonols, flavanones, isoflavones, anthocyanidins, chalcones, and catechins. They're found in a wide variety of plant-based foods, including fruits, vegetables, legumes, red wine, and green tea (including decaffeinated forms of green tea).
Stilbenes include resveratrol, which is found in small quantities in red wine and peanuts.
Lignans are found in legumes, cereals, grains, fruits, algae, and some vegetables.
Eating a balanced diet with fruits, vegetables, whole grains and legumes should provide you with a wide variety of polyphenols. Some polyphenols, such as epigallocatechin gallate (EGCG) and resveratrol, are available as dietary supplements. Always speak to your health care provider before taking large doses of dietary supplements.Sources:
American Cancer Society. "Phytochemicals." Accessed June 24, 2011. http://www.cancer.org/Treatment/TreatmentsandSideEffects/ComplementaryandAlternativeMedicine/HerbsVitaminsandMinerals/phytochemicals.
Manach C, Scalbert A, Morand C, Rémésy C, Jiménez L. "Polyphenols: food sources and bioavailability." Am J Clin Nutr. 2004 May;79(5):727-47.