Tuesday, August 4, 2009
What is it? Green tea has been used in China, India, and other eastern countries^ both as a beverage and medicinally for centuries. In the west, black tea is by far the more common tea, but green tea is making great strides as a beverage in the west. Green tea is prepared by steaming the leaves then allowing the leaves to dry, while black tea has an added step in that it is allowed to ferment.
Because green tea is not allowed to ferment, green tea contains many compounds that would other wise be lost during the fermentation process. Both forms of tea contain caffeine. In recent years, companies have now been offering green tea extracts, which highly concentrate the active compounds in green tea.
What is it supposed to do?
Green tea contains a long list of compounds that appear to have all sorts of biological effects, from increasing metabolic rate, to being powerful anti oxidants and immune modulators. The major active compounds in green tea extracts are: polyphenols (catechins) and flavonols. These two major categories are broken down into many sub groups of active compounds such as flavanoids, epigallocatechin gallate, epicatechin gallate, epicatechin, epigallocatechin and tannins, as well as other active constituents, including varying amounts of caffeine.
Studies suggest epigallocatechin gallate or EGCG appears to be the most powerful of the catechins. Some research shows it has up to 100 times greater
antioxidant activity than vitamins C and E! As most readers of this ebook should know by now, oxidative stress is associated with a long list of diseases, such as cancer, heart disease, immune suppression, and many other pathologies.
From a weight loss point of view, green tea extracts may offer some real benefits to the dieter. Green tea and green tea extracts do contain small amount of caffeine. Caffeine is known to increase energy levels, help the body to liberate stored body fat for energy, and other functions well known to most people (readers should review the ephedrine/caffeine chapter for more info on caffeine).
Although caffeine alone has the above properties, recent studies have shown green tea may be superior to simple caffeine for liberating stored body fat as a fuel and may be superior to simple caffeine for energy levels and enhanced metabolic rate. Studies have found that the catachins in green tea inhibit the enzyme that breaks down norepinephrine (catechol Omethyltransferase), while caffeine inhibits the cyclic AMP degrading enzymes (phosphodiesterases); also green tea extract may have a greater effect on thermogenesis. It should also be highly synergistic when combined with other thermogenic compounds.
Green tea has a wide range of potential health benefits. As mentioned above, various compounds in green tea extracts act as anti-oxidants, it may also reduce blood pressure, prevents LDL cholesterol from oxidation, may prevent certain forms of cancer, improve immunity, help prevent heart disease, and control blood sugar.
Epidemiological studies suggest that people who drink green tea have significantly lower risks of many diseases, including cancer, heart disease and stroke. Laboratory studies show that green tea extract protects against, and may
be an effective treatment for, many common degenerative diseases as listed above. Green tea catechins are potent anti#oxidants that provide health benefits beyond their ability to neutralize free radicals. Heart disease and stroke are associated with a number of risk factors, yet the surprising news is that green tea appears to mitigate many of these risk factors.
Green tea has been shown to lower LDL cholesterol and serum triglyceride levels. The potent anti#oxidant effects of green tea appear to inhibit the oxidation of LDL cholesterol in the arteries. The oxidation of LDL cholesterol plays a major contributory role in the formation of atherosclerosis. The formation of abnormal blood clots (thrombosis) is the leading cause of heart attack and stroke, and green tea has been shown to inhibit abnormal blood clot formation as effectively as aspirin. When looking at coagulation risk factors in the blood, green tea specifically inhibits platelet aggregation and adhesion via effects that differ from those of aspirin.
Green tea reduces the risk of arterial blood clotting by two known mechanisms. First, green tea inhibits thromboxane A2 formation, as does aspirin. Second, green tea inhibits another clotting agent called "platelet activating factor" (PAF). Reducing thromboxane A2 levels is highly desirable. High thromboxane levels not only cause arterial blood clots, but also cause arterial constriction. The inhibition of thromboxane can prevent a heart attack or a thrombotic stroke. Green tea also has been shown to elevate levels of HDL, the good cholesterol that helps remove atherosclerotic plaque from arterial walls. Note that aspirin has some antithrombotic effects that differ from green tea, such as inhibition of cyclooxygenase.