Saturday, March 17th is St. Patrick’s Day. In honor of this auspicious holiday, I felt that discussing something green would be appropriate. Next to plain water, tea is the most frequently consumed beverage in the world, with documentation of its use in China dating back at least 3000 years. Green tea, especially, was believed to promote health and longevity. Today, there is a growing body of scientific evidence that it does have specific health benefits. So, lest I ‘tease’ you further, let’s see why. . .
The Japanese began drinking green tea about 800 AD after Buddhist monks returning from their studies in China brought it back as a medicinal beverage. In fact, the monk Eisai wrote a book,Maintaining Health by Drinking Tea, in 1211 stating, “Tea is a miraculous medicine for the maintenance of health. Tea has an extraordinary power to prolong life. Anywhere a person cultivates tea, long life will follow. In ancient and modern times, tea is the elixir that creates the mountain-dwelling immortal.” If those claims seem a little ‘steep’ for you tea-lovers, I understand–but there is some truth–so don’t bag it completely!
Although there are many teas, there is only one plant. That plant is Camellia sinensis, a relative of the flowering camellia, so well known to gardeners in temperate climates. The top leaves of this plant are used to make all kinds of tea. . .whether it be green, black, or Oolong (excluding ‘herb teas’ which, in fact, are properly called infusionsrather than true teas anyway) Tea is an evergreen shrub which can attain heights of 60 feet in the wild. However, bushes cultivated for harvest are continually pruned to maintain a height of about three feet. All tea leaves are plucked in the same manner; the subsequent processing is what determines their color and character. And, as Kermit knows, it’s “not easy being Green.” Green tea in plucked, then processed in three stages within the same day. As soon as possible after plucking, the leaves are panfired or steamed to render them soft and pliable and to destroy enzymes that would otherwise lead to fermentation. Next, the leaves are rolled on heated trays to reduce moisture content. Workers manually perform this task of rolling. . .using fingers, palms, and sometimes whole forearms to spread the leaves evenly. Firing in large mechanical dryers completes the drying process, so that the final product contains only two percent or less of its original moisture. In contrast to green tea, black tea leaves are dried, rolled, fermented, and roasted. As a result, the beneficial effects of the polyphenols are decreased in this more extensively processed form. Okay, if you’re starting to see green with all this information, read on.
Green tea contains a powerful class of antioxidants called polyphenols. From a previous Insight, you know that antioxidants protect us from the harmful effects of free radicals. Such effects include developing of heart disease, cancer, and a host of age-related conditions. There are studies in progress to assess the health benefits of green tea in reducing the incidence of various cancers (especially those involving the gastrointestinal tract),decreasing progression of atherosclerosis, and decreasing the incidence of dental caries.The decrease in tooth decay and gum disease noted in routine green tea consumers is probably a combined effect of its mild antibacterial properties coupled with the antioxidant properties of polyphenols.
The catechin subclass of polyphenols (especially Epigallocatechin-3-gallate (EGCG)) seem particularly powerful as antioxidants. These polyphenols have received the greatest attention in the clinical trials studying green tea’s anti-cancer benefits. It appears that catechins can reduce not only the generation of cancers but also decrease the growth rate of cancers which have already developed. Decreased cancer mortality rates in the highest green tea consumption areas of China and Japan led to the early interest in this phenomenon. Now, animal studies specifically evaluating cancer-fighting potential are underway as well.
Topical application of green tea can protect skin from ultraviolet damage by action as a natural sunscreen. In experimental animals, topical application of EGCG stopped the development of skin cancer after exposure to carcinogenic chemicals. One Chinese study has suggested that green tea may counteract the cancer-promoting effects of female hormones on breast tissue; but more study in this area is needed to make conclusive statements. Too, EGCG may work on the heterocyclic amines that are formed when meat, poultry, and fish are grilled to prevent the cancerous changes initiated by formation of these by-products.
Additional health benefits include an antidiarrheal effect of the tannins, a benefit in mild asthmatics because of the bronchodilation effect of the small amount of theophylline present in tea, and perhaps a variable cholesterol-lowering effect (especially in regular consumers of Tao Cha, a specific green tea). The caffeine in tea is a stimulant, and even the early Chinese Buddhists realized that it could help the devout stay awake during long meditations. For those of you with a tendency to ‘meditate’ at work, green tea may help in that arena as well! Whether it is beneficial in Alzheimer’s and arthritis remains to be seen. But, it definitely acts as an astringent when used topically, so a multitude of wrinkles seem to disappear. . .at least for a little while when it is dabbed appropriately.
And, of course, never underestimate the mental benefits of tea time. The preparation and consumption of tea constitute a ritual in Japan, and the “time outs” which such rituals foster help us to relax and unwind. Tea time can be a contemplative time if solo, or a time of relaxed communion with friends and family if shared with others. So, if you’re brewing thoughts of making tea a regular part of your diet, I hope I’ve given you the green light this week.
Stephen L. Hines, M.D.
March 2001
