Green Tea For Better Health

Learn how sipping on this hot beverage can improve your life.


| June/July 2001



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Vitex agnus-castus, also known as chaste tree, has been used to treat menstrual difficulties for centuries.


What we think of as the health benefits of green tea today are not the result of controlled clinical studies, but only hints of positive effects that emerged from epidemiological literature from the late 1980s onward. These studies attempt to associate dietary and other factors with health outcomes. Results in epidemiology—the study of the incidence of disease in populations—are complicated by numerous factors that could account for either an increase or decrease of disease in a certain population. Such factors include lifestyle habits, differences in home and work environments, alcohol consumption, smoking, diet, and climate. Many epidemiological studies have shown that a diet rich in foods such as vegetables, fruits, legumes, grains, and green tea, and dietary supplements such as vitamins C and E, beta-carotene, and selenium can reduce the risk of cancer. This has encouraged researchers to try to identify chemicals in foods that help to protect against DNA damage. Many of these substances block specific carcinogen pathways.

Epidemiological, laboratory cell cultures, and animal studies have shown that green tea or its polyphenols may protect against many types of cancer. Epidemiological studies often point the way to new research. For example, prostate cancer affects as many as one out of eleven American men. It is the second-leading cause of cancer deaths among men in the United States, and is one of the most invasive forms of cancer. Epidemiological observations show that tea-consuming populations have much lower rates of prostate cancer than non-tea drinkers. The prostate cancer rate among green-tea drinking Chinese men is the lowest in the world. Of course, other risk factors such as smoking may also contribute to higher cancer rates.

In one study on green tea, researchers at the Korea Research Institute of Chemical Technology examined the effect of green tea (and coffee) on men who smoke cigarettes using a measure for a blood compound that indicates a greater predisposition to cancer development. The scientists divided fifty-two clinically healthy men into four different groups. One group was made up of non-smokers, the second group contained smokers, the third group included smokers who drank green tea, and the fourth group was made up of smokers who drank coffee. In the last two groups, the men averaged ten cigarettes a day and two to three cups of their chosen beverage.

The men were monitored for six months. Researchers found that the smokers who drank green tea had levels of the target compound similar to that of nonsmokers. Those who smoked and drank coffee did not have significantly different levels of the marker compound than smokers who did not drink stimulant beverages. This study implies that consuming green tea could help protect smokers from cancers. Of course, so could quitting smoking!

Green and black tea contain different types of flavonoids and antioxidants that may prevent certain forms of cancer (including lung, stomach, esophagus, duodenum, pancreas, liver, breast, colon, and skin cancers in laboratory animals) and reducing the risk of cardiovascular disease. A recent epidemiological study of 8,552 residents in Saitama Prefecture, Japan, evaluated green tea for the prevention of cancer and cardiovascular disease. Analysis of the data showed that there was a relative decrease in the cancer risk of people who consumed more than ten cups a day, compared with individuals who consumed only three cups daily. A Japanese “cup” of tea is probably equivalent to about 4 fluid ounces (or about half of a standard 8-oz. cup). The average decrease in cancer risk was about 60 percent. This study also showed that drinking green tea produced a significant delay in the onset of cancers. A relative decreased risk of death in cardiovascular disease of about 58 percent was also observed.

Despite the fact that much of the evidence on green tea comes from epidemiological studies, and that blinded, controlled, randomized clinical studies are few and far between, the evidence for the health benefits of green tea heavily tips in favor of positive effects. It appears that consuming an average of four standard cups of green tea daily can produce positive benefits for helping to prevent some cancers and improving cardiovascular function. Besides, the caffeine helps to keep you awake.





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