This article concerns the health effects of drinking tea. The word "tea" is limited to its traditional meaning, which is an infusion made from the plant Camellia sinensis.

Claims have been made regarding the health benefits of tea consumption since the beginning of its history 5,000 years ago.

The possible beneficial health effects of tea consumption have been suggested and supported by some studies, but others have not found beneficial effects. One should consult a doctor before using high concentrations of tea for disease prevention. Ingestion of large amounts of tea may cause nutritional and other problems because of the strong binding activities of tea polyphenols and the caffeine content, although no solid data exist concerning harmful effects of tea consumption. ^*

Benefits from green tea

Some scientific studies ^* indicate that green tea may be helpful for the following health conditions:

• Atherosclerosis
• High cholesterol
• Cancer
• Bladder cancer
• Breast cancer
• Colorectal cancer
• Esophageal cancer
• Lung cancer
• Pancreatic cancer
• Prostate cancer
• Skin cancer
• Stomach cancer
• Inflammatory bowel disease
• Diabetes
• Liver disease
• Weight loss
• Cognitive impairment

Studies claim that the polyphenol content of green tea has antioxidant properties that can help prevent cancer, however research is ongoing. There is also a suggestion that it can increase endurance in exercise by improving fat metabolism.

An article in New Scientist magazine (20 March 2004) mentions that numerous studies suggest that green tea protects against a range of cancers, including lung, prostate and breast cancer. The reason is the antioxidant epigallocatechin gallate (EGCG), according to Hirofumi Tachibana's team at Kyushu University in Japan. Their research showed that growth of human lung cancer cells that have a cell receptor called 67 LR is slowed significantly after drinking just two or three cups of green tea, which contains EGCG. The research also showed that 67 LR is involved in the propagation of prion diseases such as mad cow disease in humans. So knowledge of EGCG's effect on 67 LR might have implications in the treatment of these diseases too. (Full report in Nature Structural and Molecular Biology, DOI:10.1038/nsmb743).

According to the U.S. National Cancer Institute, in laboratory studies using animals, catechins inactivated oxidants before cell damage occurred, reduced the number and size of tumors, and inhibited the growth of cancer cells. White tea is said to be even more effective. However, human studies have proven more contradictory, perhaps due to such factors as variances in diet, environments, and populations. White tea has more catechins than any other known product, with green tea a close second. However, white tea does tend to cost more money than green tea.

Clinical trials conducted by the University of Geneva in Switzerland indicate that green tea raises metabolic rates and speeds up fat oxidation. In addition to caffeine, green tea contains catechin polyphenols that raise thermogenesis (the rate at which calories are burned), and hence increases energy expenditure.

There is also epidemiological evidence that drinking green tea (but not black tea or oolong tea) may help prevent diabetes, although it is worth noting that this is evidence of an association, but that prospective studies are needed to confirm the effect.

A 2006 study showed that elderly Japanese people who consumed more than 2 cups of green tea a day had a 50 per cent lower chance of having cognitive impairment, in comparrison to those who drank less than 2 cups a day, or who consumed other tested beverages. Ref: //www.foodnavigator.com/news/ng.asp?id=66142. Green tea has 67.5 mg catechins per 100 ml, and this might explain the results. The study was published in "The American Journal of Clinical Nutrition" (Vol. 83, pp.355-361).

United States FDA

In a July, 2005 review of claims made about the health benefits of green tea, the U.S. Food and Drug Administration concluded that it was highly unlikely that green tea reduces the risk of breast and prostate cancer. Further, the FDA believes that current evidence does not support qualified health claims for green tea consumption and a reduced risk of cancer. The FDA has not been able to square its findings with the findings of extensive tea experiments in Asia.

See also

• Tea
• Green tea
• White tea

External links

• FDA says studies supporting assertions that Green Tea lowers cancer risk are weak
• Green tea information from the University of Maryland Medical Center
• Some evidence for the benefits of green tea for endurance in exercise
• Tea and Cancer Prevention - National Cancer Institute press release
• Antioxident in Green Tea May Fight Alzheimer's, (EGCG)

References