Green Tea
FAMILY: Theaceae.
HABITAT: native to China and Japan, now also extensively cultivated in India and south-east Asia.
USED PART: leaves.
PHARMACEUTICAL PREPARATIONS: dry extract titrated in total epigallocatechins min. 5% and in total flavonoids min. 4%. Its daily dosage ranges from 5 to 7 mg/kg, in two administrations morning and evening on an empty stomach.
THERAPEUTIC PROPERTIES: An in vitro study examined the antiradical and antioxidant action of green tea, fruit and vegetables, presenting the results as vitamin C equivalents. Green tea was found to have a very strong antioxidant and anti-radical action, while fruit and vegetables showed a significant but significantly lower action. One cup of green tea provides antioxidant and anti-radical activity comparable to that of five portions of raw fruit or vegetables or 400 mg of vitamin C. Thanks to this action, green tea has antioxidant action on LDL (bad cholesterol particles), thus helping to prevent atherosclerosis.
A controlled clinical study evaluated the effect of green tea on vascular function and free radical damage versus placebo. Young, healthy women were enrolled, receiving either a green tea extract by mouth or a placebo for 5 weeks while measuring vascular function by Doppler flowmetry and the concentration of oxidised LDL in the blood. It was seen that the average diameter of the artery in the arm afterwards increased significantly after treatment with the extract. Green tea also significantly reduced the concentration of oxidised LDL and antibodies The study indicates that a green tea extract improves vascular function and reduces LDL oxidation in women.
A controlled clinical study evaluated the antioxidant and anti-inflammatory effects on the skin of green tea given both orally and topically. Forty women with ageing skin were enrolled who either took 600 mg per day of green tea extract by mouth and simultaneously applied a cream containing 10% green tea to the skin or took a placebo either systemically or topically for 2 months. It was seen that the skin of the subjects in the green tea group showed a significant improvement in elastic tissue content on microscopic examination, while some of the patients in the verum group reported mild skin irritation after the application of green tea cream. The study indicates that green tea can improve the elastic tissue content in the skin after 2 months of treatment, thus making it more youthful and elastic.
A controlled clinical study evaluated whether a green tea extract could reduce blood pressure, cholesterol and triglycerides, and free radical damage in 111 healthy adult subjects aged 21-70 years. They received 2 cps per day of green tea extract by mouth or a placebo for 3 weeks, measuring before and after the therapy blood pressure, cholesterol, triglycerides and free radical damage indicators. It was seen that at the end of the trial, green tea extract reduced systolic (maximum) blood pressure by 5 mm/Hg and diastolic (minimum) blood pressure by 4 mm/Hg and lowered indicators of free radical damage. Total cholesterol was reduced by 10 mg/dl and LDL (bad) cholesterol by 9 mg/dl in subjects in the green tea group. No significant side effects were reported. The study indicates that a green tea extract reduces blood pressure, LDL cholesterol and free radical damage in humans, thus helping to provide prevention against cardiovascular diseases.
SIDE EFFECTS: A study by the American Pharmacopoeia evaluated existing studies on the safety of green tea. 216 cases of adverse reactions to green tea were observed, of which 34 involved liver problems. 27 of these 34 reports on liver disorders were classified as possible causes and 7 as probable causes. The study indicates that if green tea and its extracts are of good quality and used in the correct way, there should be no major toxicity problems.
CONTRAINDICATIONS: caution in people with liver problems. It can be used during pregnancy, during lactation and in children.
DRUG INTERACTIONS: a green tea extract reduces the bioavailability of clozapine, a psychopharmaceutical, in the rat.