For centuries, individuals have consumed green, black and oolong teas for their health benefits. While no official dosage for green tea exists, the University of Maryland Medical Center generally recommends drinking 2 to 3 cups daily. While most scientific evidence supports the health benefits of green tea, some investigations suggest that the consumption of large amounts of the polyphenols in green tea may actually be harmful. Consult your doctor before drinking green tea.
Components
Green tea contains many potent antioxidants called polyphenols, which may prevent disease by destroying dangerous cell-damaging free radicals. Free radicals may increase the risk of some cancers and heart disease. The polyphenols in green tea are considered safe when taken in moderation. Chung Yang of New Jersey's Rutgers University recommends drinking no more than 10 cups daily.
In addition, green tea contains the strongest polyphenols, called catechins, as well as the most powerful type of catechin, epigallocatechin gallate, or EGCG. Catechins may provide protection against viruses and dangerous bacteria as well as help promote weight loss. Green tea also contains caffeine.
Disease
Drinking up to 10 cups of green tea daily may benefit diseases such as breast cancer and heart disease. The University of Maryland Medical Center cites an observation of 472 women in different stages of breast cancer. Women consuming the most green tea experienced less metastasis, or spreading, and women in early, undiagnosed stages who drank at least 5 cups of green tea daily had fewer incidents of reoccurrence after treatment. In addition, women under 50-years-old who drank 3 or more cups a day had a 37-percent-less chance of developing breast cancer when compared to women who didn't consume tea.
Drinking 9 or 10 cups of green tea daily may produce cardiovascular benefits such as helping prevent coronary artery disease and lowering cholesterol levels, according to syndicated health columnists Joe and Terry Graedon. Although evidence is promising, green tea has not been approved by the FDA as a treatment for cancer or heart disease.
Weight Loss
Some clinical evidence suggests that a combination of green tea and caffeine can improve weight loss and weight maintenance in overweight and moderately-obese people, according to the University of Maryland Medical Center. Weight loss that results from drinking green tea is often attributed to its catechins, which may stimulate fat metabolism in the liver. An observation cited by the Japanese Health Information website Healthhokkaido regarding the effects of green tea on weight loss discovered that drinking 5 to 6 cups for 12 weeks burns body fat. Though potentially beneficial, further scientific evidence is needed to conclusively prove the effectiveness of green tea as a treatment for weight loss.
Considerations
The polyphenols in green tea may cause liver and kidney damage when consumed in large amounts. However, problems are most likely to occur only in people taking polyphenol supplements in amounts 50 times greater than the 50 to 150 mg in one cup of green tea, according to Yang. In addition, a study published in the March 2007 edition of the journal "Chemical Research in Toxicology" discovered that dogs and rats consuming high doses of the catechin EGCG suffered toxicity and death. Green tea may interact with certain medications or dietary substances and may adversely affect certain medical conditions. Before drinking green tea, consult your doctor.
References
- University of Maryland Medical Center: Green Tea; 2011
- "NewScientist" magazine: Green Tea Can Be Harmful in Large Quantities; May 2007
- Healthhokkaido.com: Health Benefits of Green Tea; 2006
- "Chemical Research in Toxicology"; Possible Controversy Over Dietary Polyphenols: Benefits vs Risks; Joshua D. Lambert, et al.; March 2007
- The People's Pharmacy: Green Tea; Joe Graedon, et al.; Oct. 2005
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