The Role of Green Tea in Cancer Prevention

Over the past 20 years, researchers have been studying the potential of green tea and its components to prevent cancer. Green tea extract and catechins have been identified as particularly important in the fight against cancer, and further research is ongoing.

The Three Hurdles

For the efficacy of green tea against cancer to be academically recognized, three hurdles must be completed. The first hurdle is the establishment of epidemiological data that shows a relationship between the amount of green tea consumed and the rate of cancer/death from cancer. The second hurdle is experimental data that supports the epidemiological data, and the third hurdle is human experimentation and clinical testing to confirm efficacy. Currently, researchers are in the third stage.

Epidemiological Studies

Several studies have been conducted to demonstrate the relationship between green tea consumption and cancer prevention. For instance, a report showed that drinking green tea was associated with a lower death rate from stomach cancer in Shizuoka prefecture and Kita-kyushu district. Similarly, the National Cancer Research Center in the United States confirmed that green tea can suppress the occurrence of esophageal cancer based on research conducted in Shanghai, China. However, reports on the efficacy of drinking tea against cancer are still insufficient, and there is a lack of data on black tea versus cancer prevention.

Experimental Data

Numerous studies have been conducted using animal models and in vitro experiments to support the efficacy of green tea extract and catechins against carcinogenicity. However, some animal experiments have shown that the amount of green tea consumed does not always correlate with its effectiveness. Additionally, in a multi-organs medium stage cancer model, the efficacy of green tea catechins was not uniform, leaving room for further research. The anti-cancer mechanism of green tea is categorized into several types, including anti-mutagenic, anti-cancer promotion, anti-cancer progression, anti-mutagenic increase of cancer cells, anti-metastasis, and apoptosis guidance. Catechins have been shown to be effective in each category, and no other food components have such diverse control effects.

Assimilation, Metabolism, and Excretion

There is a lack of data on the assimilation, metabolism, and excretion of green tea catechins in animals and humans. However, it is known that several percent is assimilated and most is excreted. Further analysis is required to fully understand the process.

Effective Amount

The effective amount of green tea catechins needed to prevent carcinogenicity is 20mg/day for 1kg of body weight based on epidemiological data and 10mg/day based on animal experiments. In human testing, the recommended amount is 20mg/day. One to two grams of green tea (about three cups) is recommended for a Japanese person who weighs 50-60kg. Studies have shown that cancer patients who drank more than 10 cups of green tea per day experienced a delay in cancer progression, while breast cancer patients who drank more than five cups per day had a lower rate of recurrence.

Future Applications

Green tea and its components will likely become a common addition to the diet for cancer prevention. Additionally, it may be used as a medicine for high-risk groups. Collaborative research between Japanese institutions and the National Cancer Research Center in the United States and the Texas University MD Anderson Cancer Center is currently underway. In the near future, green tea and its components may become a common medicine for those at high risk of cancer.