Overview
Green tea contains unfermented mature tea leaves, while oolong tea uses semi-fermented leaves. Both contain substances called polyphenols in greater quantities than fully fermented black tea. These polyphenols may contribute to a healthier body. Polyphenols occur in different concentrations and in different forms in both types of tea. Of the two, green tea appears to contain a higher concentration of polyphenols and may have the most health-giving properties.
Polyphenols
Polyphenols work as antioxidants. That means they absorb compounds in the body called free radicals. Left in the body, free radicals can cause harm to living cells and even alter genetic material within a cell. As experts from the University of Maryland Medical Center point out, these free radicals are linked to conditions such as heart disease and general ageing in the body. Polyphenols also occur in foods such as berries, legumes and some cereals. However, green and oolong tea offer some of the highest doses of polyphenols in the diet.
Green Tea
Green tea contains a form of polyphenols known as catechins. In a 1999 study published in the American Journal of Clinical Nutrition, scientists from the University of Geneva established a link between catechins and raised fat oxidization in the body. This means that green tea polyphenols may temporarily increase metabolism of body fat. Green tea is so rich in polyphenols that many health food stores now stock green tea extract in the form of pills.
Oolong Tea
Oolong tea contains a lower concentration of polyphenols than green tea, but a higher concentration than traditional black leaf tea. However, a 2005 study by Dr. David Shafer from the University of Texas at Tyler suggests that oolong tea may contain some polyphenols not found in green or black tea. He linked these oolong polyphenols with lowered blood sugar, something that may help in diabetes prevention and treatment, though the tests are not conclusive.
Cancer
Polyphenols from both green and oolong tea may help improve overall health. However, polyphenols appear to have a particular link with slightly reduced levels of cancer. Countries where people drink a lot of green and oolong tea often have low cancer rates. Research cited by the University of Maryland also points to lowered risk of breast cancer in women, as well as reduced chance of the disease spreading in affected women who drink green tea.
References
- University of Maryland Medical Center; Green Tea; David Zieve et al.; Sep. 20, 2010
- Oregon State University; Tea and Chronic Disease Prevention; Jane Higdon, Ph.D.; Nov. 2002
- University of Texas at Tyler; Oolong Tea A Drink To Your Health; Mar. 24, 2005
- The American Journal of Clinical Nutrition; Efficacy of a Green Tea Extract Rich In Catechin Polyphenols and Caffeine In Increasing 24-h Energy Expenditure and Fat Oxidation in Humans; AG Dulloo et al.; Dec. 1999
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