Green Tea 'A cup of tea?' 'Make it green!':
Three types of tea:
As Caesar divided Gaul into three parts, real tea, not the herbal sort, can also be divided into three types. Although all teas are derived from the evergreen shrub Camellia sinensis, the methods used to process the tea leaves vary.
Black tea is fermented, oolong is partially fermented, and green tea is unfermented. Green tea is prevented from fermentation by treating the freshly cut leaves with hot steam before drying. The heat inactivates an enzyme, polyphenol oxidase, which was released when the leaves were cut. If allowed to ferment, this enzyme would inactivate much of the polyphenol content of the tea, the chemicals which we think give it much of its health benefit. Polyphenol chemicals, many of them catechins, may make up as much as 30% of the dry weight of green tea.
In vitro (test tube) studies show that the components of green tea, particularly the catechins, have powerful antioxidant effects, even comparable to the preservative butylated hydroxyanisol (BHA). They inhibit LDL oxidation (the process that leads to blocked arteries) better than Vitamin C, act as potent oxygen scavengers (preventing the biological equivalent of rusting), and block the activity of certain bacteria including those that cause cavities.
In vivo (in living critter) studies with animals confirm the usefulness of green tea catechins. The strong antioxidative effects protect brain cells from injury. They lower cholesterol when it needs to be lowered and prevent and cure diabetes in rats poisoned with a diabetes inducing chemical. They prevent cavities in rats infected with the bacteria that should have caused cavities.
Human studies suggest that the effects seen in test tube and animal studies will probably translate over to us. In Japan, various studies have associated high consumption of green tea with decreased cholesterol and triglycerides and an increase of good cholesterol. Tea drinkers have fewer signs of liver damage, fewer strokes, and more regular less smelly bowel movements. The later probably because green tea polyphenols inhibit the growth of bacteria such as Clostridium botulinum, Staphyloccus aureus, and Vibrio cholera, all of which are considered nasty when they inhabit your intestine. On the other hand tea polyphenols seemed to help the growth of acidophilus bacteria which are considered the "good guys" and beneficial to bowel health.
Cancer Prevention and Treatment:
Where green tea is probably getting the most attention is in cancer treatment. Breast cancer incidence in Japan is a fraction of what it is in the United States. Researchers are working hard to explain this difference as due to differences in diet. Some research suggests that it is the high consumption of soy beans and soy protein based in foods that gives Japanese women the protection against breast cancer. Others are suggesting that at least some of the protection comes from green tea. Studies show that it may exert multiple actions against cancer, including inhibition of tumor initiation and inhibition of growth and metastasis. in a 1998 study published in the Japanese Journal of Cancer Research (Nakachi K, Suemasu K, et al. Influence of drinking green tea on breast cancer malignancy in Japanese patients. 1998;89:254-261) women who drank alot of green tea had fewer recurrences of stage 1 or stage 2 breast cancer.
How much green tea should one drink?
Research varies of course but the beneficial effect is somewhere in the 5-10 cup a day range. This seems like alot of tea but keep in mind that green tea has about one third the caffeine of a cup of coffee. Substitute green tea for a two cup a day coffee habit and you are up to six cups of tea a day to avoid your caffeine withdrawal headache. There isn't much evidence that argues for coffee. Sorry Starbucks.
Green tea extracts that are decaffeinated are now sold in capsule form, 300-400 mg doses of standardized (80%) extracts are a commonly suggested dose. The soy protein formula, Isoprotein plus, which we sometimes suggest at our office has 500 mg of green tea extracts per serving.
Green Apple Iced Tea for a hot Denver summer:
3 parts green tea leaf
1 part mint tea tea leaf steep strong, 2 Tb per cup water. Strain
Add equal volumes of cold apple juice to the tea and serve in a tall glass filled with ice.