PJ Online | Green tea (Dietary supplements)

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Pharmaceutical Journal
Vol 267 No 7177 p823
8 December 2001

Dietary supplements summary

(2) Green tea

Description Green tea is prepared from the steamed and dried leaves of Camellia sinensis, a shrub which grows in eastern Asia. Green tea contains polyphenols (catechins), tannins and methyl-xanthines (eg, caffeine, theophylline, theobromine). Green tea extract is available in tablets and capsules with typical doses of 100–300mg (as catechins).
Action Green tea reportedly has antioxidant properties, attributed primarily to the polyphenols, and protects against damage to cells. High consumption of green tea has been linked with a reduction in low-density lipoprotein (LDL) cholesterol, a decrease in the oxidation of LDL, an increase in high-density lipoprotein (HDL) cholesterol, and inhibition of thromboxane formation and platelet aggregation. Green tea polyphenolics have been shown to have anticarcinogenic and antibacterial properties in vitro and in animals.

Reported uses Chinese and Japanese populations have used green tea and its extract for thousands of years.

Claims for this substance include the prevention of cardiovascular disease, cancer, viral and bacterial infections (including AIDS) and dental caries. Epidemiological studies have linked high intakes of green tea with decreased risk of atherogenesis and cardiovascular disease, but controlled trials using green tea as a drink or supplement in humans have failed to show a substantial lipid lowering effect.

Preliminary associations (from epidemiological research) have been made between higher green tea consumption and reduced incidence of cancers of the breast, prostate, stomach, pancreas, colon and lung, but further research is needed to confirm this effect.

Green tea can be recommended as a healthy drink, but there is far less research on green tea supplements, and more research is needed on their safety and efficacy before definite recommendations for their value can be made.
Adverse effects None known.

Precautions Hypersensitivity to green tea. Pregnant and breast-feeding women should avoid green tea supplements pending long-term safety studies. Use with caution in people with a history of bleeding or haemostatic disorders.

Interactions Theoretically, green tea may enhance the effect of drugs affecting coagulation or platelet aggregation (eg, aspirin, warfarin, clopidogrel).

Many people who visit pharmacies want to buy or are already taking some form of dietary supplement. This series includes supplements either that are commonly sold in pharmacies and those which have attracted recent media interest, possibly resulting in the public wanting further information about them.

Each monograph covers the actions, possible uses, adverse effects, precautions and interactions, and is intended to be an aide-memoire for pharmacists advising their customers and patients. However, it should be emphasised that these monographs are summaries only, and readers who want more in-depth information, particularly details of research studies providing evidence on the use of these supplements, should consult other texts.

The series is written by Dr Pamela Mason (a pharmacist with a postgraduate qualification in nutrition)