Polyphenols are naturally occurring compounds found in plant foods. These compounds offer a number of important health benefits, including protecting cells from damage by free oxygen radicals. A number of studies have been done to determine the effects of polyphenols on cholesterol levels and the prevention of cardiovascular disease.
Food Sources of Polyphenols
Polyphenols are found in a wide variety of fruits, vegetables, nuts and seeds, as well as in cocoa, tea and coffee. Grapes, grape juice and red wine are high in resveratrol, a polyphenolic compound that has been shown to have powerful antioxidant properties. Apples and onions are rich in quercetin, another polyphenol with powerful antioxidant properties. Tea is yet another source of polyphenols called catechins.
Effects of Resveratrol on Cholesterol
Grapes, grape juice and red wine are high in resveratrol, a polyphenol. Polyphenol-rich grape extracts have been shown to decrease low-density lipoprotein cholesterol or bad cholesterol, according to an 2008 article in "Nutrition Research." Lower levels of low-density lipoprotein cholesterol can be beneficial in preventing cardiovascular disease.
Effects of Quercetin on Cholesterol
Researchers at Florida State University in Tallahassee assessed the long-term effect of apples on the cardiovascular health of160 women between the ages of 45 and 65. One group of women were given 75 g of dried apples every day for a year, while the other group was given 75 g of prunes for a year. At the end of the study, researchers found that the women who ate dried apples every day for a year lowered their total cholesterol by 14 percent and their levels of LDL or "bad" cholesterol by 23 percent. This effect was not seen in the group who ate prunes.
Effects of Catechins on Cholesterol
Studies show that catechins, a class of polyphenols found in green tea, may lower cholesterol levels. According to a study published in "Obesity," Japanese men and women who consumed green tea containing 583 mg of catechins for 12 weeks had a greater decrease in low-density lipoprotein cholesterol than those who consumed 96 mg of catechins.
Significance
High blood cholesterol levels, particularly high levels of low-density lipoprotein cholesterol, may increase the risk of cardiovascular disease. Polyphenols such as resveratrol, quercetin and catechins have been shown to lower cholesterol levels. These cholesterol lowering effects may be due in part to their ability to reduce inflammation and the peroxidation of lipids, both of which are linked to increased risk for heart disease. Researchers suggest that further studies are needed to determine how polyphenols reduce cholesterol levels.
References
- "Nutrition Research"; Cardioprotective Actions of Grape Polyphenols; W.R. Leifert et al.; November 2008
- MedlinePlus; An Apple a Day May Help Keep Heart Disease Away; April 2011
- "Obesity"; A Green Tea Extract High in Catechins Reduces Body Fat and Cardiovascular Risks in Humans; Tomonori Nagao et al.; 2007
