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Green Tea: Health Benefits and Applications.

Dean, College of Agriculture, California State Polytechnic University, Pomona

Green Tea: Health Benefits and Applications. edited by Yukihiko Hara. New York: Marcel Dekker, 252 pp, 2001.

Since the late 1980’s green tea, green tea extracts and tea flavonoids have been studied intensively because of close relationships to decreased incidents in cancer, heart disease and several other human diseases. This book focuses on the health benefits of the tea polyphenols.

The book is well written and enjoyable to read, emphasizing contributions by Dr. Hara and his laboratory. The chapter sequence is thoughtful, summarizing the history (Chapter 1), biosynthesis of catechins and methods of extraction (Chapters 2 and 3), science related to mechanisms of action and associated health benefits (Chapters 5 through 17), toxicology and safety (Chapter 18) and industrial applications and tea products in Japan (Chapters 19 and 20). The tables and figures are effectively used. The cited references are historically important, identifying Dr. Hara’s publications and a few related supportive citations.

The antioxidant effect of catechins (Polyphenon 60, an extract mixture) was demonstrated to be better than alpha-tocopherol and BHA. The antioxidant function was expressed in food application models and in diet studies.

The polyphenolic components of tea are effective against various strains of foodborne pathogenic bacteria, such as Clostridium botulinum, Clostridium perfringens, Vibrio parahaemolyticus, Vibrio fluvialis, Vibrio metschnikovii, Staphylococcus aureus, Bacillus cereus, Plesiomonas shigelloides and Aeromonas sobria. Other organisms were less affected. Methicillin resistant Staphylococcus aureus (MRSA) is a serious problem in hospitals, causing septicemia, endocarditis, respiratory infection and infection of urinary passages. Epigallocactechin (ECG) effectively decreased MRSA. In addition, green tea catechins (polyphenon 100) were shown to produce a synergistic inhibition of antibiotic resistant organisms. Tea catechins also inhibited expression of many viruses at concentrations less than 10 ppm, including human papilloma virus, influenza virus in mice, pseudorabies virus, bovine herpes virus, porcine transmissible gastroenteritis virus and porcine epidemic virus.

The catechins were demonstrated to have antimutagenic activity, to inhibit chromosome aberrations and to inhibit TPA induced neoplastic transformation. Tea catechins inhibit growth of tumor cells implanted under the skin, but not when cells were injected into the peritoneal cavity. Epidemiological evidence indicates a decrease in Helicobacter pylori, which is related to ulcers and stomach cancer. Catechin application eliminates Helicobacter within one month. Only ECg appears to inhibit invasiveness of cancer, presumably by inhibition of collagenase released by the tumor cell.

GTC addition to high fat/high cholesterol diets decreased fat and cholesterol absorption (greater fecal excretion), HDL-C was not affected, but GTC decreased the increase in LDL caused by the diet. It takes gram quantities to have an effect in humans—increased HDL, but no effect on total cholesterol.

Human consumption studies indicate 1 g of catechins per day is frequently consumed. An LD50 of 2.8 mg/g would reflect a dose of 143 g/50KgBW. The equivalent of 1,000 cups of tea. Thus, it is not anticipated that any acute or lethal toxicity would be observed by oral intake of tea catechins. Long term feeding studies indicated modest toxicologic expression. In humans, patients carrying H. pylori or hepatitis C virus have been given capsules of catechins (900–1200 mg/day) for years and no toxicity has been reported.

The book is a worthy addition to any reference library on tea catechins and their health benefits. It definitely promotes the health benefits of these unique polyphenolic compounds. Students will enjoy reading the volume to gain a perspective of how quickly a phytochemical can be identified and systematically studied to identify clearly specific and unique health benefits at physiologic exposure concentrations. The weakness of course is the focus of the book on a single researcher’s research without a perspective of related contributions from other scientists.

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