Green tea and cancer
Green tea, derived from the leaves of the Camellia sinensis plant, is renowned for its high antioxidant content, particularly polyphenols and flavonoids like catechins. These compounds have been studied for their potential roles in health maintenance, including cancer prevention and treatment. Research indicates that green tea may be linked to a reduced risk of certain cancers, particularly stomach cancer in populations with high green tea consumption, such as those in Asia. Laboratory studies suggest that its antioxidants can inhibit cancer cell growth and restrict blood supply to tumors, potentially aiding in cancer management.
However, clinical evidence regarding green tea's cancer-fighting properties is mixed. While some studies show promising correlations, including potential benefits for lung cancer in more recent research, others, such as those conducted by the National Cancer Institute and in the UK, have found little to no significant impact on cancer incidence. Due to these inconsistencies, the FDA has called for more controlled studies to explore the relationship between green tea and cancer further. Additionally, while generally safe in moderation, excessive consumption of green tea can lead to side effects, particularly due to its caffeine content, which may pose risks for individuals with specific health conditions.
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Green tea and cancer
ALSO KNOWN AS: Camellia sinesis
DEFINITION: Green tea is a beverage made from fresh leaves of the evergreen Camellia sinesis plant. These leaves are rich in antioxidants, including polyphenols and flavonoids, which have been implicated in such general body health as suppressing aging, deterring food poisoning, controlling blood pressure, glucose, and cholesterol levels, and preventing cancer. One class of flavonoids, the catechins, has recently become the focus of study for their anticancer potential.
Cancers treated or prevented: Implicated in both the treatment and the prevention of several cancers
Delivery routes: Most commonly oral by liquid; green tea tablets and capsules containing its main ingredients are also widely marketed
How this substance works: Studies have suggested relationships between green tea intake in the diet and the reduction of stomach cancer in people of Asian descent. Laboratory studies of animal subjects strongly suggest that green tea may also help reduce the incidence of a number of cancers. The cancer-fighting components of green tea are antioxidants, which are the body’s defense against free radicals that precipitate cell dysfunction that, in turn, leads to cancer. Antioxidants in green tea include polyphenols and flavonoids such as epigallocatechin gallate (EGCG) and other catechins. EGCG binds with laminin receptors on the surface of cancer cells, thereby dramatically reducing their growth and survival. It may also restrict blood flow to cancerous cells and restrict or eliminate the formation of new blood vessels, both of which contribute to the death of cancer cells, which are unable to obtain needed nutrients for growth. Laboratory studies have also suggested that catechins may inhibit the formation and operation of specific enzyme activities that lead to cancer development.
Human studies have been much less consistent. Some studies support laboratory findings regarding green tea cancer-fighting benefits, but other studies suggest little or no benefit. Studies in China, where green tea is a staple in the diet, generally find lower incidences of cancer among tea drinkers when compared to non–tea drinkers. The National Cancer Institute (NCI), however, conducted its own study of the antitumor effect among prostate cancer patients. This study concluded that there was little to no benefit. A similar study conducted in the United Kingdom in 2020 also found an inconsistent relationship between green tea and a reduction in cancer diagnoses. Still, other studies conducted in the 2020s found green tea has both preventative and therapeutic benefits for lung cancer. However, in response to these differing results, the Food and Drug Administration (FDA) has denied that green tea has antitumor benefits. It suggests that further controlled studies on the relationships between green tea and cancer are needed.
Side effects: Side effects from drinking large amounts of green tea in the diet are normally rare among most of the population. Green tea has a high caffeine content; however, physicians routinely warn that people with heart conditions or high blood pressure and women who are pregnant or breastfeeding should not drink green tea in excess. Some side effects of caffeine may include nausea, insomnia, frequent urination, irritability, or diarrhea. In excessive doses, caffeine can cause seizures or heart irregularities. Green tea also contains vitamin K, which can decrease the effectiveness of anticoagulant drugs.
Bibliography
Abe, Sarah K., and Manami Inoue. "Green Tea and Cancer and Cardiometabolic Diseases: A Review of the Current Epidemiological Evidence." European Journal of Clinical Nutrition, vol. 75, no. 6, 2021, pp. 865-876, doi.org/10.1038/s41430-020-00710-7. Accessed 13 June 2024.
“Green Tea - Complementary and Alternative Therapy.” Cancer Research UK, 12 Oct. 2022, www.cancerresearchuk.org/about-cancer/treatment/complementary-alternative-therapies/individual-therapies/green-tea. Accessed 13 June 2024.
Preedy, Victor R. Tea in Health and Disease Prevention. London: Academic, 2013.
Trisha, Anuva T., et al. "Tea Polyphenols and Their Preventive Measures against Cancer: Current Trends and Directions." Foods, vol. 11, no. 21, 2022, doi.org/10.3390/foods11213349. Accessed 13 June 2024.
Zeng, Long, et al. "Green Tea Consumption and Risk of Pancreatic Cancer: A Meta-analysis." Nutrients, vol. 6, no. 11, 2014, pp. 4640-4650, doi.org/10.3390/nu6114640. Accessed 13 June 2024.