Antioxidants protect your body from free radical damage due to smoking, pollution, sun exposure, toxins and as a by-product of normal metabolism. An article published in January 2005 in "The American Journal of Clinical Nutrition" states that polyphenols are the most abundant types of antioxidants in the diet.
Phenolic Acids
Phenolic acids are derived from either benzoic acid or cinnamic acid. Edible plants don't contain significant amounts of benzoic acids, except red fruits and black tea. Cinnamic acid derivatives are more common and include p-coumaric, cafferic, ferulic and sinapic acids. A study on polyphenols published in May 2004 in "The American Journal of Clinical Nutrition" states that caffeic acid is the most abundant phenolic acid found in fruit and ferulic acid is the most abundant phenolic acid found in cereal grains.
Flavonoids
Flavonoids include flavonols, flavones, flavanones and isoflavones. The study on polyphenols published in May 2004 in "The American Journal of Clinical Nutrition" states that flavonols are most abundant in onions, kale, leeks, broccoli and blueberries, while flavones are found in celery and parsley, flavanones are found in tomatoes, mint and citrus fruits, and soybeans are the source of isoflavones. Proanthocyaninds are flavonoids that give wine its astringency and anthocyanins are pigments that give fruits and flowers their colors.
Stilbenes
Stilbenes are not common in the diet; however, resveratrol has been studied extensively and is available as a dietary supplement. It's naturally found in red wine, but according to the study on polyphenols published in May 2004 in "The American Journal of Clinical Nutrition," it is unlikely to provide any protective benefits at normal nutritional intakes.
Lignans
Lignans are converted to enterodiol and enterolactone by intestinal bacteria and absorbed into the blood where they show weak estrogennic activity. Flaxseeds are the richest source of lignans, but they are also found in other seeds, grains, legumes, fruits and vegetables. According to 2010 information from the Linus Pauling Institute, the role of lignans in disease prevention is not clear.
References
- "The American Journal of Clinical Nutrition"; Polyphenols: Foods Sources and Bioavailability; Claudine Manach; May 2004
- "The American Journal of Clinical Nutrition"; Polyphenols: Antioxidants and Beyond; Augustin Scalbert; January 2005
- Linus Pauling Institue at Oregon State University; Lignans; January 2010
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