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The weight-reducing effects of tea: The difference between green, oolong and black tea
Thursday, July 08, 2010 7:01 am Email this article
There are three types of tea: black, oolong and green.
Of the three, oolong is traditionally reported to have an weight-reducing effect as well as a cholesterol- and triglyceride-lowering effect according to Han et al (1999).
Here is the difference between the three according to the book Green Tea and the Stash Tea Company’s website (http://www.stashtea.com).
Black tea has been fully oxidized or fermented.
The fresh tea leaf is withered by exposure to air, and is broken and left to ferment after picking. It yields a hearty-flavored, amber-colored tea. World-wide, 72 percent of the tea produced is black tea.
Teas such as English Breakfast, Darjeeling and Orange Pekoe are black teas.
Oolong tea is treated similarly to black tea, but the withering process is much shorter, resulting in a partly fermented (oxidized) leaf.
It is a cross between black and green tea in color and taste and is sometimes known as the “champagne of teas”. Oolong tea is popular in China.
The highest grade of Oolong teas, Formosa Oolongs, are grown in Taiwan. Milk, lemon, and sugar are not usually added to oolong tea.
Green tea is not oxidized at all.
It is steamed immediately after harvesting to stop the fermenting process, then rolled and dried. It has a more delicate taste and is light green/golden in color. Ten percent of the world’s tea production is green tea. Green tea is a staple in the Orient.
The health-promoting/cancer-fighting effects of tea are thought to be due to substances in tea called catechins.
Catechins are a subgroup of naturally occurring antioxidants called polyphenols that are found in some fruits and vegetables, potatoes and garlic according to the book Green Tea (p. 7).
There are five types of catechins: gallocatechin, epicatechin, epigallocatechin, epicatechin gallate and epigallocatechin gallate—which is the most potent of the catechins (p. 12).
Catechins are found in wine, Ginkgo biloba leaves and pine bark, but are found in the greatest quantity in fresh tea leaves.
However fermentation reduces the catechin content. Therefore, unfermented green tea contains 15-30 percent catechins by dry weight; partially fermented oolong tea contains 8-20% catechins; and fully-fermented black tea contains 3-10% catechins (p. 7-8).
Other mechanisms at work?
Two other aspects of tea may be at least partially responsible for the anti-obesity action of oolong tea, and green tea, according to a great little paperback book titled Green Tea by Nadine Taylor, M.S., R.D., (Kensington Books, 1998).
Catechins found in tea have a weight-reducing effect and inhibit amylase, the pancreatic enzyme responsible for the digestion of starches.
Han LK, Takaku T, Li J, Kimura Y, Okuda H. Anti-obesity action of oolong tea. International Journal of Obesity and Related Metabolic Disorders, 1999 Jan, 23(1):98-105.
Taylor N. Green Tea. Kensington Books. New York, 1998.
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