Green tea is produced from unfermented leaves of the Camellia sinensis plant, the same plant that produces oolong and black teas. Commonly brewed and drunk as a hot or cold beverage, green tea is also available as a concentrated extract. Green tea offers many health benefits and is generally considered safe; however, green tea components may cause side effects in susceptible individuals. As with any supplement, check with your health care provider before adding green tea to your diet.
Heart Disease
Green tea is rich in antioxidants, compounds that mop up cell-damaging free radicals. The antioxidants in green tea appear to lower triglycerides and LDL, or "bad," cholesterol while raising HDL, or "good," cholesterol, factors that help prevent heart disease. The University of Maryland Medical Center states that with the consumption of three cups of tea per day, heart attack rates decrease by 11 percent, although the Food and Drug Administration concludes that there is no credible evidence to support these claims.
Cancer
The antioxidants found in green tea may help prevent cancers of the breast, bladder, skin, pancreas and colon. Specific antioxidants called catechins inhibit cancerous growths, explains the National Cancer Institute. While both black and green teas contain antioxidants, green tea offers higher levels of cancer-fighting catechins. Steep green tea for at least five minutes to release the maximum amount of antioxidants, and avoid instant teas, as they contain very low catechin levels.
Weight Loss
Concentrated green tea extracts may help with weight loss in moderately obese people. According to Creighton University Medical Center, catechins found in green tea boost metabolism which increases energy expenditure. Brewed green tea does not provide the level of catechins needed to see this effect, however, so you must supplement with a concentrated green tea extract instead. Use under the supervision of your health care practitioner to monitor for unwanted side effects.
Caffeine Toxicity
Although green tea contains less caffeine than oolong or black teas, it is still a significant source of this central nervous system stimulant. Caffeine is a diuretic and may lead to dehydration when consumed in large quantities, warns the Mayo Clinic. It is also habit-forming and may lead to unpleasant withdrawal symptoms if you stop taking it abruptly. Caffeine may also worsen stomach ulcers by increasing the production of gastric acids. Drink green tea in moderation, and avoid concentrated green tea extracts if you are sensitive to the effects of caffeine.
Drug Interactions
Green tea shows anti-platelet activity and therefore may increase the blood-thinning effects of medications such as warfarin or aspirin. Green tea may cause dangerously high blood pressure if you take it along with monoamine oxidase inhibitors, medications used to treat depression. Green tea appears to interfere with prostate cancer chemotherapies, and the University of Maryland Medical Center recommends avoiding green tea if you are undergoing treatment. Discuss any potential drug interactions with your health care provider if you regularly consume green tea.
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