Green Tea – Protecting Against Cancer
The anticancer properties of green tea are largely the result of the ability of polyphenols to black the formation of carcinogenic compounds in the body. In addition, polyphenols trap and detoxify enzymes that produce carcinogens, rendering them harmless and inhibiting the spread of cancer cells. EGCG (the most common catechin in green tea) contributes to the programmed death of cancer cells before they can multiply and begin forming tumors.
Green tea appears to be most effective against cancers of the gastrointestinal tract, including stomach cancer, small intestine cancer, pancreatic cancer and colon cancer; lung cancer; and estrogen-related cancers, including breast cancer. The Japanese custom of drinking green tea with meals is thought to be a major factor in the low rates of these types of cancer in Japan.
Lowering Cholesterol Levels
Cholesterol is essential for life, but it is also a major factor in the development of cardiovascular disease. There are basically two types of cholesterol: HDL (“good” cholesterol) and LDL (“bad” cholesterol). LDL cholesterol deposits cholesterol in the arteries; HDL cholesterol removes it. When too much LDL cholesterol circulates in the blood, it accumulates in the arteries, leading to atherosclerosis – hardening of the arteries. Atherosclerosis, especially in conjunction with high blood pressure, is a prime risk factor for heart disease. Compounds in green tea have been shown to reduce levels of bad LDL cholesterol and increase levels of good HDL cholesterol, thus helping to prevent atherosclerosis and heart disease.
In 1992, Japanese researchers examined the health records of 1,306 male retirees and discovered an inverse relationship between green tea consumption and serum cholesterol levels; in other words, men who drank more green tea had less cholesterol in their blood. Five years later, researchers in Hong Kong tested the effects of a variety of tea extracts on lipid profiles in rats. They reported that Chinese green tea decreased cholesterol levels without affecting HDL cholesterol levels, thus improving HDL ratios.
Reducing Blood Pressure
High blood pressure (hypertension) is a serious risk factor for heart disease, stroke and other cardiovascular diseases. Some risk factors for hypertension – such as age, race and family history – can’t be controlled. However, many major risk factors – such as poor diet, obesity and lack of exercise – are lifestyle related. Green tea consumption, it appears, is one lifestyle choice that can reduce the risk of hypertension.
In 1995, Japanese researchers published the results of a study on the effects of green tea on blood pressure in rats. The researchers gave rats green tea, water or specially processed green tea with a high concentration of gamma-aminobutyric acid (GABA, a naturally occurring amino acid-like substance). In the American Journal of Hypertension, the researchers reported that the GABA-rich green tea lowered blood pressure in rats with preexisting hypertension and protected healthy rats against blood-pressure increases caused by a high-salt diet.
That these findings might apply in humans was supported by the results of a large study published in 2004 in the Archives of Internal Medicine. Researchers in Taiwan surveyed the tea-drinking habits of 1,507 patients with newly diagnosed hypertension. They found that habitual tea drinkers – those who drank at least 120 milliliters of tea daily for at least one year – were 46 percent less likely to develop hypertension than non-habitual tea drinkers. Those who drank more than 600 milliliters of tea daily were 65 percent less likely to develop hypertension.