Green tea is made from the unfermented leaves of the Camellia sinensis plant, native to East Asia. It is a popular beverage. It contains chemicals called catechins that provide immense medicinal value. It has been used traditionally to treat a variety of conditions including heart and liver diseases, cancer, inflammatory bowel disease and obesity. Green tea supplements are available as capsules, teas and liquid extracts. The dose and form may vary, depending on your age, health history and purported use.
Green Tea and Immune System
The polyphenols of green tea prevent the suppression of the immune system induced by ultraviolet radiations, according to a study published in the February 2010 issue of the journal “Cancer Prevention and Research.” This may, in turn, be responsible for the anticancer and infection fighting ability of green tea. The University of Maryland Medical Center also states that 250 to 500 mg of green tea per day can exert significant antioxidant, anticancer and immune activity, and thereby help prevent and treat a variety of infections including those of the urinary tract.
Green Tea and Digestion
Green tea catechins such as epigallocatechin gallate can interfere with emulsification and digestion of lipids in the digestive tract and prevent the absorption of dietary fat and cholesterol, report the researchers of a study published in the March 2007 issue of the “Journal of Nutritional Biochemistry.” This may lower the level of fats in the blood and reduce the risk to cardiovascular diseases. Another study published in a 2007 issue of the journal “Obesity” reaffirms that regular intake of green tea extracts reduces the body fat and cholesterol levels, may thereby, lower the incidence of obesity and heart disease.
Side Effects
It is generally safe to consume moderate amounts of green tea. However, the beverage and supplements contain significant amounts of caffeine, which may lead to side effects such as insomnia, irritability, anxiety, increased heart rate and dizziness. Caffeine overdose can also lead to nausea, vomiting and diarrhea. Green tea may also interfere with certain blood-thinning, contraceptive and chemotherapy medications.
Precautions
Although green tea is commonly available at most stores, you should consult a doctor before using it for medicinal purposes. The Food and Drug Administration does not regulate the production of green tea supplements in the United States so it's imperative that the supplement you intend to use has been tested for safety and efficacy. Look for the USP logo issued by the U.S. Pharmacopoeial Convention on supplement labels that have been submitted by their manufacturers for safety tests.
References
- "Cancer Prevention and Research"; Drinking Green Tea Prevents UV-Induced Immunosuppression by Rapid Repair of UV-Induced DNA Damage and Enhancement of Nucleotide Excision Repair Genes; Santosh K. Katiyar, et al.; February 2010
- University of Maryland Medical Center: Urinary Tract Infections
- "Journal of Nutritional Biochemistry"; Green Tea as Inhibitor of the Intestinal Absorption of Lipids: Potential Mechanism for its Lipid-Lowering Effect; Sung I. Koo, et al.; March 2009
- "Obesity"; A Green Tea Extract High in Catechins Reduces Body Fat and Cardiovascular Risks in Humans; Tomonori Nagao, et al.; 2007
- University of Maryland Medical Center: Green Tea
