It is no exaggeration to say that entire cultures and empires have been formed on the basis of tea. The growth, processing, shipping, and sale of tea play a huge role in the histories of such countries as China, India, and Britain. Today, the bulk of the world’s green tea is grown throughout Asia and parts of the Middle East and Africa.1

While Westerners traditionally consume black tea, recently there has been a tremendous increase in the popularity of green tea. In fact, hundreds of millions of people throughout the world now consume this drink.1

Background

Archeologic findings show the consumption of tea dates back at least 5,000 years.2 Specifically, green tea (Camellia sinensis) emerged early on as a medicinal remedy for everything from fatigue to bladder problems.2 The Kissa Yojoki (Book of Tea), the first known publication detailing the health benefits of this herb, was written by the Buddhist priest Eisai in 1191 and described green tea’s impact on the “five vital organs,” especially the heart.2

More recent publications tout such potential benefits as weight loss, lowered cholesterol levels, and improved mental alertness. In addition, green tea is being studied for its potential impact on cancer, rheumatoid arthritis, infections, and immune disorders.3

Scientific data

The three main varieties of tea are green, black, and oolong. They are all made from the same plant; the difference is in the age and size of the leaf when it is picked and in the processing of the leaf before consumption. Green tea is made from fresh, steamed, unfermented leaves that are then dried before consumption.

This organic method is key to the preservation of the maximum amount of green tea’s active antioxidant chemicals (processing with heat destroys many of those properties).1 Green tea also contains significant amounts of theobromine, theophylline, and caffeine—although much less caffeine than traditionally brewed coffee (Table 1).3

The health benefits of green tea are attributed to its rich content of at least six catechin polyphenols, particularly epigallocatechin gallate (EGCG). EGCG is an extremely powerful antioxidant. A study conducted at the University of Kansas in Lawrence found EGCG to be at least twice as powerful as resveratrol, a polyphenol found in red wine that limits the negative effects of smoking and a fatty diet. This may explain why the incidence of heart disease among Japanese men is very low, despite the fact that nearly 75% smoke.

Clinical trials have verified positive antioxidant effect from drinking green tea. To date, however, no health claims to this end have been approved by the FDA. Perhaps one of the largest and most credible investigations was published recently in JAMA. In that study, more than 40,000 Japanese adults were followed for up to 11 years for death from all causes and for up to seven years for death from a specific cause. The results showed 16% lower risk of all-cause mortality and a 26% lower risk of cardiovascular disease (CVD) death among those who consumed five or more cups of green tea a day compared with those who drank less than one cup of tea a day. The study included this stunningly significant statement: “If green tea does protect humans against CVD or cancer, it is expected that consumption of this beverage would substantially contribute to the prolonging of life expectancy, given that CVD and cancer are the two leading causes of death worldwide.”4

Dose, how supplied

Most green tea products are sold as dried tea. Liquid extracts and powder-filled capsules are also available, as are decaffeinated products. The recommended therapeutic daily consumption is 240-320 mg of tea a day (usually two to three cups), or 300-400 mg a day of standardized green tea extract.1 Alternatively, approximately one teaspoon of dried leaf tea brewed for two to three minutes per 6-oz cup of hot (not boiling) water (180°F-190°F) will also provide the recommended strength of tea.2

Safety, interactions

Due primarily to the potential stimulant action, pediatric use has not been studied and is not recommended. For similar reasons, green tea consumption in pregnant or lactating women is not recommended. As always, those with botanical allergies should proceed with caution whenever using a new product.

Several potential drug/herb interactions exist. Due to stimulant effects, those with heart disease, kidney disorders, stomach ulcers, and psychological disorders should obtain clearance from a healthcare provider before using green tea. Green tea can potentially extend the antiplatelet effect of aspirin and should be used with caution with any anticoagulant.1 Any psychotropic drugs, sedatives, antidepressants, and lithium can be antagonized by green tea.2 If there is concern over the stimulant-related cautions but the antioxidant effect is felt to be warranted, a decaffeinated product may be used instead.

Cost

Green tea is a very inexpensive product in its most basic form (typically less than $0.25 per cup). Most major tea manufacturers offer a wide selection of flavors and varieties, which can be found in grocery and specialty stores.

Summary

Given certain aspects of our coffee culture, a transition to green tea would seem to be a wise decision. A product this safe, tasteful, inexpensive, and potentially beneficial rarely presents itself. Many people already take a daily vitamin. All emerging data seem to indicate that the addition of daily green tea consumption would be even more beneficial.

References

1. University of Maryland Medical Center. Green tea. Available at www.umm.edu/altmed. Accessed June 7, 2007.

2. Wikipedia. Green tea. Available at www.en.wikipedia.org/wiki/Green_tea. Accessed June 7, 2007.

3. About.com. Chinese food. Available at www.chinesefood.about.com. Accessed June 7, 2007.

4. Kuriyama S, Shimazu T, Ohmori K, et al. Green tea consumption and mortality due to cardiovascular disease, cancer, and all causes in Japan: the Ohsaki study. JAMA. 2006;296:1255-1265.

Ms. Sego is a staff clinician at the Veterans Administration Hospital in Kansas City, Mo., where she practices adult medicine and women’s health. She also teaches at the nursing schools of the University of Missouri and the University of Kansas.