Green tea, a tea made from the leaves of a plant native to Asia called Camellia sinensis, is used as an ingredient in foods, beverages and dietary supplements. The major health-promoting benefits of green tea come from antioxidant components such as epigallocatechin, or EGCG. Research on green tea demonstrates some effects including mental alertness, reducing risks and progression of certain types of cancer and increasing blood pressure in hypotensive individuals. Use of dietary supplements should be discussed with an individual's medical doctor prior to use.
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Use of green tea may cause nausea, vomiting, gas, and diarrhea; as well as central nervous system side effects such as difficulty sleeping, dizziness, irritability, and confusion. High doses of green tea are more likely to produce side effects in users. Green tea-containing dietary supplements should always be taken as directed on the product labels.
Interactions with Drugs and Nutrients
The caffeine in green tea can cause adverse side effects. Common drugs that may have negative interactions with green tea include amphetamines, anti-diabetics, birth control, estrogens, blood thinners, blood pressure medications, quinolone antibiotics and medications known to harm the liver. Dietary supplements or food products containing caffeine or other central nervous system-stimulating ingredients such as guarana and bitter orange should be limited with green tea. Iron absorption of food and folic acid metabolism may also be affected by green tea dietary supplements.
Interactions with Medical Conditions
Although dietary supplements are sometimes thought to reduce symptoms of medical conditions, they can exacerbate some conditions as well. Those with anemia, high blood pressure and other cardiovascular conditions, diabetes, osteoporosis, clotting disorders, anxiety disorders and liver disorders should discuss the risks and benefits of green tea dietary supplements as they pertain to their individual health.