Black, green and oolong tea are all abundant in flavonoids that may have noteworthy health benefits. All of these varieties are made from the Camellia sinensis plant. While observational studies point to a relationship between black or green tea consumption and reduced risk for cancer, cardiovascular disease and other conditions, conclusive evidence of this link has yet to be established. The flavoinoid content in black tea differs from that in green tea.
Processing Effect
The way the teas are processed determines their flavonoid content. Flavonoids are members of the polyphenol family believed to have health benefits. Black tea, which is fully fermented, is highest in theaflavins and thearubigins while having a modest content of catechins. Green tea, which is unfermented, is the opposite. Catechins make up the majority of the flavonoids in green tea. Theaflavins, thearubigins and catechins all are responsible for antioxidant action in tea, notes a 2005 review published in "Preventive Medicine."
Flavonols
Black tea is also a good source of flavonols, another type of flavonoids. Flavonols found in tea derived from Camellia sinensis include quercetin, myricitin and kaempferol. Processing does not have much impact on tea's flavonol content, so green tea and black tea have similar amounts. Flavonols such as quercetin also are antioxidants.
Flavonoid Significance
The antioxidant action provided by flavonoids in tea is believed to neutralize free radicals, which are damaging particles in your body. Antioxidants also may help protect against heart disease because they help prevent damage caused by LDL, or "bad," cholesterol. However, while some antioxidants like quercetin show strong action in the lab, researchers aren't sure whether they produce the same effects inside your body, notes the University of Maryland Medical Center. While flavonoids in tea may be largely responsible for observed health benefits, other substances such as caffeine, manganese and fluoride in tea may have an influence.
Research
The way that flavonoids in tea work in your body and the benefit that each type delivers is still under investigation. For example, researchers have theorized that the catechins in green tea are responsible for improving impaired endothelial function, which refers to the function of the inner lining of your blood vessels. However, black tea and green tea are equally effective, despite the fact that green tea has a much higher catechin content, according to a 2008 study published in the "British Journal of Nutrition."
References
- Linus Pauling Institute, Oregon State University; Tea and Chronic Disease Prevention; Jane Higdon, Ph.D.; November 2002
- University of Maryland Medical Center; Vitamins -- Phytochemicals; Harvey Simon, M.D.; February 2009
- "QJM"; Tea Flavonoids and Cardiovascular Health; R.A. Riemersma, et al.; 2001
- "Handbook of Antioxidants"; Enrique Cadenas and Lester Packer; 2002
- "British Journal of Nutrition"; The Efficacy of Black Tea in Ameliorating Endothelial Function Is Equivalent to That of Green Tea; N. Jochmann, et al.; April 2008
- "Preventive Medicine"; Antioxidative Properties of Black Tea; W. Luczaj and E. Skrzydlewska; June 2005
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