Green tea is made from the Camellia sinensis plant, and has been consumed as a beverage for thousands of years. Today, green tea and its extract are sometimes used for a variety of medicinal purposes, as well as to assist in losing weight. Before you start taking green tea for weight loss, talk with your doctor to discuss the potential health risks and drug interactions.
Benefits
Drinking green tea or taking green-tea extract may aid in weight loss, as well as help treat gingivitis, rosacea and diabetes, says the University of Pittsburgh Medical Center. Green tea could also help prevent cancer, the flu, heart disease, sun damage and liver disease. Other potential benefits include treating high blood pressure, gastrointestinal conditions and dementia, notes the Memorial Sloan-Kettering Cancer Center. Additionally, green tea might help treat Crohn's disease, hives, immune-system dysfunction, high cholesterol and triglycerides, leukoplakia and leukemia, according to the University of Michigan Health System. Consult your physician before using green tea to treat or prevent any medical condition, including to promote weight loss.
Function
Green tea contains tannins, polysaccharides, flavonoids, polyphenols such as epigallocatechin gallate (EGCG), fluoride and caffeine, according to the Memorial Sloan-Kettering Cancer Center. Specifically, the EGCG and caffeine content in green tea are thought to offer the weight loss actions by speeding up your metabolism, notes the University of Michigan Health System. EGCG and the other polyphenols in green tea are also thought to provide anticancer effects through their antioxidant actions.
Dosage
The usual dosage of green tea extract is 100 mg to 150 mg three times daily, says the University of Pittsburgh Medical Center. Green tea extracts are commonly standardized to contain 50 percent EGCG and 80 percent total polyphenols. Alternatively, you could make a tea by steeping a teaspoon of green tea leaves in a cup of boiling water for three minutes and drinking the tea up to four times daily, notes the University of Michigan Health System. Ask your doctor about the safe and effective amount of green tea or extract to consume before you start taking it.
Scientific Evidence
Taking green tea extracts improved weight loss in overweight children in a Japanese study published in a 2008 issue of Obesity. Another clinical trial found that green tea extract enhanced weight loss in overweight women over three months, according to an issue of Clinical Nutrition" published the same year. A study in Physiology & Behavior in 2007 found that green tea improved weight loss, notes the University of Pittsburgh Medical Center. Some studies have failed to find weight-loss benefits from green tea, however. For example, a 2005 study published in the Journal of the Society for Gynecologic Investigation found that green tea did not stimulate substantial weight loss among women with polycystic ovary syndrome.
Warnings
Although green tea beverages are generally safe, green tea extracts can cause liver inflammation in some people, warns the University of Pittsburgh Medical Center. Green tea might be unsafe for children and pregnant or breast-feeding women. Taking the extract could also interact negatively with certain medications such as blood thinners, atropine, adenosine, irinotecan, Verapamil, tamoxifen, bortezomib and codeine, cautions the Memorial Sloan-Kettering Cancer Center. Green tea may interfere with the absorption of iron and folic acid supplements, as well as interact negatively with MAO inhibitors due to the caffeine content in green tea.
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