Polyphenols are a class of chemicals in plants that offer numerous health benefits. Besides being potent antioxidants, some polyphenols possess anti-inflammatory and anticancer properties, and can play a role in the gene expression. However, the bioefficacy, or biological activities, of polyphenols in the human body depends on their bioavailability; in simple words, on how much and how fast the body can absorb and utilize them.
General Information about Polyphenols
Polyphenols are plentiful in many foods of plant origin including fruits, vegetables, whole grains, nuts, culinary herbs and spices, teas and cocoa products. Plants produce polyphenols to protect themselves from harsh climate, pathogens and oxidative stress. According to a Nov.-Dec. 2009 article in "Oxidative Medicine and Cellular Longevity," there are over 8,000 different polyphenols discovered to date. They are divided into a number of groups and subgroups.
Health Benefits of Polyphenols
Eating foods rich in polyphenols can potentially protect you from certain diseases and conditions including heart disease and cancer. According to an article in the April 2011 issue of the "Critical Reviews in Food Science and Nutrition," polyphenols found in many foods such as green tea, cocoa, red wine, various fruits and berries have proven antioxidant and anti-inflammatory properties. These polyphenols can improve endothelial function, decrease the oxidation of "bad" cholesterol, or LDL, and slow down the development of atherosclerosis, thus decreasing the risk of heart disease. Polyphenols in green and black teas, red wine, some berries, soy and turmeric can delay cancerous tumor development and growth. Some polyphenols may protect people with diabetes from serious complications, such as diabetic neuropathy, or nerve damage, and the eye damage called retinopathy.
Bioavailability of Polyphenols
To exert their benefits on human health, polyphenols need to be delivered to the body tissues in certain amounts. It means that beneficial health effects of polyphenols are highly dependable on their bioavailability. The U.S. Food and Drug Administration defines bioavailability as the rate and extent to which an ingredient is absorbed and becomes available to the site of action. Different polyphenols have different bioavailability in the human body. Some widely available and readily consumed polyphenols may have a low absorption rate, as noted in a March 2010 article in the "International Journal of Molecular Sciences." Therefore, even if you eat plenty of foods containing polyphenols, your body may absorb and utilize only a small amount. This, in turn, lowers the bioefficacy of polyphenols.
Role of Metabolites
Although you can absorb some polyphenols intact in their native forms, the majority must undergo various chemical changes within the body for absorption. As a result of such modifications, the polyphenol reaches the blood or the body tissue as a different chemical compound called a metabolite. Because the chemical structures of the initial polyphenol and metabolite can be significantly different, it is sometimes difficult to identify and evaluate all the metabolites. In addition, some people may be genetically predisposed to metabolize certain polyphenols better than the others and as such, some have more health benefits.
References
- "Oxidative Medicine and Cellular Longevity"; Plant Polyphenols as Dietary Antioxidants in Human Health and Disease; Pandey KB, et al.; Nov.-Dec. 2009
- "Critical Reviews in Food Science and Nutrition"; Effect of Flavonoids and Other Polyphenols on Inflammation; Gonzales R, et al.; April 2011.
- U.S. Food and Drug Administration: Guidance for Industry; Bioavailability and Bioequivalence Studies for Orally Administered Drug Products - General Considerations, March 2003, p.3
- "International Journal of Molecular Sciences"; Bioavailability of the Polyphenols: Status and Controversies; D'Archivio M, et al.; March 2010
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