Green tea as cancer treatment and prevention has been common topic for decades. And hundreds of medical studies have been conducted on it. While some claims are superficial, some are backed up by real medical studies.
Green tea is slightly oxidized during manufacturing, thus keeping intact its curative properties. It is very popular in China and Japan, where it is considered as one of the most effective alternative therapies to fight and prevent many medical conditions such as many cancers. Recently it is spreading more and more in the West, where traditionally people drink black tea instead.
The Anticancer Agent of Green Tea
In almost all anti-cancer diet, green tea occupies a place of excellence because it is the food that contains the most anti-cancer molecules. These anticancer agents are represented by the catechins (flavonoid family) and occupy one third of the weight of tea leaves!
Catechins have the distinction of being able to tackle many of the processes used by cancerous cells to grow. The most powerful and abundant catechin is EGCG (epigallocatechin gallate); it has, in particular, the property to suffocate cancerous cells.
In fact, when cancer cells proliferate to form a small tumor, they must necessarily form, in parallel, a network of blood vessels to be fed and to be able to reproduce. This is called angiogenesis. EGCG has the property of preventing development of angiogenesis, which is indispensable for the formation of any malignant tumor and growth. This is one of the most interesting finding in research conducted on green tea and cancer prevention.
However, it role in preventing cancer is somewhat controversial. Although the cell cultures and animal models show that epigallocatechin-3-gallate (EGCG), the main polyphenol found in green tea, has potent anti-inflammatory and anti-proliferative capable of selectively inhibiting cell growth and inducing apoptosis in cancer cells without affecting normal cells, its effectiveness is not fully proven in humans in certain studies, according to some researchers.
Green Tea and Lung Cancer
A study presented January 11, 2010 at a conference sponsored by the American Association for Cancer Research (AACR) and the International Association for the Study of Lung Cancer (IASLC) demonstrated that green tea protect smokers from lung cancer. Dr. Lin Hsin-I, from Chung Shan Medical University in Taiwan, and colleagues recruited 170 people with lung cancer and 340 healthy patients as controls. Participants were questioned about their daily routine: the number of cigarettes smoked, the number of cups of green tea consumed, their dietary intake of fruits and vegetables, cooking methods, and family history of lung cancer. The results show that smokers and nonsmokers who do not drink green tea are five times more likely to develop lung cancer than those who drink at least one cup of green tea per day. Smokers who did not drink green tea are twelve times more likely to be diagnosed with the disease than those who drink at least one cup of green tea per day. Other studies on green tea and lung cancer confirm these findings.
Green Tea and Cancer Prevention
The potential role of green tea in preventing cancer is of great interest in the scientific community. This interest was first motivated by epidemiological studies suggesting an association between green tea and cancer prevention, certain cancers. Subsequently, studies in animal models have shown that catechins are capable of inhibiting the growth of cancerous cells in certain organs such as breast, lung, esophagus, prostate, liver, and skin. There are, however, few clinical studies to corroborate the effects of green tea in humans.
In 2005, following an allegation application for anticancer properties of green tea, the Food and Drug Administration (FDA) stated that there was no scientific evidence of an effect of tea green on the following cancers: colon, rectum, stomach, lung, pancreas, and ovaries. For breast and prostate, the FDA came to the conclusion that its preventive effect is very unlikely.
Green Tea and Endometrial Cancer
In 2009, a meta-analysis of epidemiological studies showed a correlation between green tea and endometrial cancer; regular consumption reduces the risk considerably. The authors of the study, however, draw attention to the fact that the number of studies on the subject is low and the amount of green tea used is difficult to quantify. Another study published the same year found the same results, an association between green tea consumption (5-6 cups per week or daily cup) and reduced risk (23%) of endometrial cancer.
Green Tea and Ovarian Cancer
There are few studies on Green Tea and Ovarian Cancer. However, it is found that women who drink at least two cups per day have at least 46% less risk for developing ovarian cancer. This observation was also reported in another study published in 2002.
Green Tea and Prostate Cancer
The link between green tea and prostate cancer prevention is still difficult to assess. Some population studies show a correlation between reduced risk and increased tea consumption. Others conclude that this is not the case. The results of clinical studies are still few, though promising. Volunteers with BPH at risk of cancer evolution took 600 mg tea catechins daily for one year. At the end of treatment, the rate of cancer was diagnosed only 3% instead of 30% in the control group. There are more studies being conducted on Green Tea and Prostate Cancer; hopefully more light will be shed.
Green Tea and Breast Cancer
The data on green tea and breast cancer are mainly epidemiological and few. They suggest that tea consumption may reduce the risk of breast cancer occurrence and limit its recurrence. The effect would observe from 3 to 5 cups per day. Other studies suggest that the practice does not reduce the risk of breast cancer among Asian women however. Research on Green tea and breast cancer prevention is highly controversial. While the big companies claim there is no real proof the practice really helps women avoiding the disease other independent studies claim completely otherwise.
Green Tea and Esophageal Cancer
Epidemiological studies have also shown that consumption of 2 to 3 cups of tea per week, from February to March, reduces the risk of esophageal cancer. This effect is especially found in women. However, the results of these studies have been contradicted by another study on Green Tea and Esophageal Cancer performed on people with precancerous lesions of the esophagus. After consuming 5 mg tea extract daily for 11 months, no improvement in the condition of the lesion has been shown.
Green Tea and Oral Cancer
A preliminary study suggests that consumption of green tea extract, precisely 3 times daily after meals, for 12 weeks, helps prevent cancer of the mouth, compared to placebo. This clinical study conducted on 39 participants at risk of cancer of the mouth is confirmed by a study of greater magnitude on green tea and mouth cancer.
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