Herb: Green Tea

GreenTea2What is Green Tea?

Green tea, also known as unoxidized tea, is made solely from the leaves of the camellia sinensis plant. The leaves are plucked, slightly withered, then immediately cooked to preserve the green quality and prevent oxidization. As a result of these methods, green teas have a much higher concentration of chlorophyll, polyphenols, and antioxidants than other types of tea. The growing conditions for green tea can be broken down between two different types: sun grown and shade grown. The leaves are generally harvested three times a year with the first flush producing the highest quality leaves. The heating process differs greatly depending on the region and the tea maker’s techniques. Some of the mainstream methods of manufacturing green tea include:

Pan Firing – Chinese green teas are often pan or wok roasted to neutralize the natural enzymes, and then dried, which generally results in a pale green color.

Steaming – Most Japanese green teas are quickly deep steamed resulting in a bright green infusion.

Different Varieties of Green Tea

The difference between green and black tea results from the manufacturing process. Black tea undergoes fermentation which transforms its color and flavor, whereas green tea remains unprocessed and retains its color. Green tea is grown in higher altitudes, more specifically the mountainous regions of East Asia. Some green tea is still picked by hand, and it is thought that handpicked teas are less bitter and yield a sweeter, more robust taste. Other factors such as the climate and soil can also affect the flavor.

Sencha is the most popular of Japan’s green teas. There are numerous grades which can affect the price and quality. Sencha leaves are first steamed and then shaped. Sencha tea produces a clear yellow/green tea with a sweet, grassy but slightly astringent flavor.

Matcha is made from green tea leaves grown in the shade. The leaves have a higher chlorophyll content which makes them a vibrant green color. To make matcha, the entire leaf is ground down into a powder. The powder is mixed with boiling water and gently whisked before being served. The flavor is light and sweet and so is now added to desserts and sweet drinks.

Green tea can be found as fresh leaves or in tea bags, frequently blended with other flavors such as lemon, lime or ginger.

When buying tea leaves, avoid older leaves. This is the same principle as with coffee beans. Allegedly, whole leaves are the highest grade and leaves that are older than four months are past their level of peak freshness. Once purchased and opened, keep leaves in an airtight container that can be resealed and store in a cool place to help slow down the reactions that can reduce the tea’s phytonutrient content and impact on flavor.

Uses & Studies with Green Tea

Used for Why
Influenza
In one study, elderly nursing home residents in Japan who gargled with a green tea extract were less likely to get the flu than those who gargled without the green tea extract.

Abnormal Pap Smear
A preliminary study found that cervical dysplasia improved following treatment with epigallocatechin-3-gallate, a green tea flavonoid, for 8 to 12 weeks.
Colon Cancer
The polyphenols in green tea leaves may help protect against colon cancer.
Down’s Syndrome
In double-blind studies of young adults with Down’s syndrome, supplementation with epigallocatechin-gallate (EGCG; a flavonoid present in green tea) significantly improved measures of cognitive function.
High Cholesterol
Green tea has been shown to lower total cholesterol levels and improve people’s cholesterol profile.
Leukoplakia
A combination of whole green tea, green tea polyphenols, and green tea pigments painted on lesions may improve healing.
Obesity
Green tea extract rich in polyphenols may support a weight-loss program by increasing energy expenditure or by inhibiting fat digestion.
Prostate Cancer
Drinking green tea or taking green tea catechins may help prevent prostate cancer in men at high risk of developing the disease.
Sunburn
Green tea contains polyphenols that have antioxidant and anti-inflammatory activity, and studies have suggested that these polyphenols can protect skin against ultraviolet rays.
Type 2 Diabetes
A meta-analysis of several studies found that green tea consumption may improve blood glucose control and insulin sensitivity.
Crohn’s Disease
Green tea is a tannin-containing herb that may be helpful to decrease diarrhea during acute flare-ups and has been used for this purpose in traditional medicine.
Hemochromatosis
High-tannin tea has been shown to reduce the need for blood removal from people with iron overload, or hemochromatosis, in an open study. The tea had to be taken with meals and without lemon or milk to be effective. Tea is believed to help in hemochromatosis by preventing iron absorption.
High Triglycerides
Drinking green tea may have a positive effect on triglyceride levels.
Hives
Two components of green tea, the polyphenols epigallocatechin (EGC) and epicatechin gallate (ECG), are reported to have an antihistamine effect.
Immune Function
Green tea has stimulated production of immune cells and has shown anti-bacterial properties in some studies.
Infection
Green tea is an herb that directly attack microbes.
Lung Cancer
Numerous preliminary studies have shown an association between drinking green tea and a reduced risk of several types of cancer including lung cancer.

List of Studies Regarding Green Tea

Graham HN. Green tea composition, consumption, and polyphenol chemistry. Prev Med 1992;21:334-50.

Kono S, Shinchi K, Ikeda N, et al. Green tea consumption and serum lipid profiles: A cross-sectional study in Northern Kyushu, Japan. Prev Med 1992;21:526-31.

Yamaguchi Y, Hayashi M, Yamazoe H, et al. Preventive effects of green tea extract on lipid abnormalities in serum, liver and aorta of mice fed an atherogenic diet. Nip Yak Zas 1991;97:329-37.

Sagesaka-Mitane Y, Milwa M, Okada S. Platelet aggregation inhibitors in hot water extract of green tea. Chem Pharm Bull 1990;38:790-3.

Stensvold I, Tverdal A, Solvoll K, et al. Tea consumption. Relationship to cholesterol, blood pressure, and coronary and total mortality. Prev Med 1992;21:546-53.

Tsubono Y, Tsugane S. Green tea intake in relation to serum lipid levels in middle-aged Japanese men and women. Ann Epidemiol 1997;7:280-4.

Serafini M, Ghiselli A, Ferro-Luzzi A. In vivo antioxidant effect of green tea in man. Eur J Clin Nutr1996;50:28-32.

Benzie IF, Szeto YT, Strain JJ, Tomlinson B. Consumption of green tea causes rapid increase in plasma antioxidant power in humans. Nutr Cancer 1999;34:83-7.

Sasazuki S, Komdama H, Yoshimasu K, et al. Relation between green tea consumption and severity of coronary atherosclerosis among Japanese men and women. Ann Epidemiol 2000;10:401-8.

Suganuma M, Okabe S, Sueoka N, et al. Green tea and cancer chemoprevention. Mutat Res1999;428:339-44.

Weisberger JH, Rivenson A, Garr K, et al. Tea, or tea and milk, inhibit mammary gland and colon carcinogenesis in rats. Cancer Lett 1997;114:323-7.

Yang CS, Lee MJ, Chen L, Yang GY. Polyphenols as inhibitors of carcinogenesis. Environ Health Perspect1997;105(Suppl 4):971-6 [review].

Menon LG, Kuttan R, Kuttan G. Anti-metastatic activity of curcumin and catechin. Cancer Lett1999;141:159-65.

Mukhtar H, Ahmad N. Green tea in chemoprevention of cancer. Toxicol Sci 1999;52(2 Suppl):111-7.

Katiyar SK, Mukhtar H. Tea consumption and cancer. World Rev Nutr Diet 1996;79:154-84 [review].

Kohlmeier L, Weterings KG, Steck S, Kok FJ. Tea and cancer prevention: an evaluation of the epidemiologic literature. Nutr Cancer 1997;27:1-13 [review].

Tsubono Y, Nishino Y, Komatsu S, et al. Green tea and the risk of gastric cancer in Japan. New Engl J Med 2001;344:632-6.

Galanis DJ, Kolonel LN, Lee J, Nomura A. Intakes of selected foods and beverages and the incidence of gastric cancer among the Japanese residents of Hawaii: a prospective study. Int J Epidemiol 1998;27:173-80.

Li N, Sun Z, Han C, Chen J. The chemopreventive effects of tea on human oral precancerous mucosa lesions. Proc Soc Exp Biol Med 1999;220:218-24.

Otake S, Makimura M, Kuroki T, et al. Anticaries effects of polyphenolic compounds from Japanese green tea. Caries Res 1991;25:438-43.

Ooshima T, Minami T, Aono W, et al. Reduction of dental plaque deposition in humans by oolong tea extract. Caries Res 1994;28:146-9.

Stoner GD, Mukhtar H. Polyphenols as cancer chemopreventive agents. J Cell Bioch 1995;22:169-80.

You SQ. Study on feasibility of Chinese green tea polyphenols (CTP) for preventing dental caries. Chin J Stom 1993;28(4):197-9.

Hamilton-Miller JM. Antimicrobial properties of tea (Camellia sinensis L.). Antimicrob Agents Chemother1995;39:2375-7.

Imai K, Nakachi K. Cross sectional study of effects of drinking green tea on cardiovascular and liver diseases. BMJ 1995;310:693-6.

Goto K, Kanaya S, Nishikawa T, et al. The influence of tea catechins on fecal flora of elderly residents in long-term care facilities. Ann Long-Term Care 1998;6:43-8.

Goto K, Kanaya S, Ishigami T, Hara Y. The effects of tea catechins on fecal conditions of elderly residents in a long-term care facility. J Nutr Sci Vitaminol 1999;45:135-41.

Kaltwasser JP, Werner E, Schalk K, et al. Clinical trial on the effect of regular tea drinking on iron accumulation in genetic haemochromatosis. Gut 1998;43:699-704.

Bettuzzi S, Brausi M, Rizzi F, et al. Chemoprevention of human prostate cancer by oral administration of green tea catechins in volunteers with high-grade prostate intraepithelial neoplasia: a preliminary report from a one-year proof-of-principle study. Cancer Res2006;66:1234-40.

Shanafelt TD, Lee YK, Call TG, et al. Clinical effects of oral green tea extracts in four patients with low grade B-cell malignancies. Leuk Res 2006;30:707-12.

Murray MT. The Healing Power of Herbs. Rocklin, CA: Prima Publishing, 1995, 192-6.

Imai K, Suga K, Nakachi K. Cancer-preventive effects of drinking green tea among a Japanese population. Prev Med 1997;26:769-75.

Imai K, Nakachi K. Cross sectional study of effects of drinking green tea on cardiovascular and liver diseases. BMJ 1995;310:693-6.

Samman S, Sandstrom B, Toft MB, et al. Green tea or rosemary extract added to foods reduces nonheme-iron absorption. Am J Clin Nutr 2001;73:607-12.

Bonkovsky HL. Hepatotoxicity associated with supplements containing Chinese green tea (Camellia sinensis)Ann Intern Med 2006;144:68-71.

Schonthal AH. Adverse effects of concentrated green tea extracts. Mol Nutr Food Res 2011;55:874-885.

Liatsos GD, Moulakakis A, Ketikoglou I, Klonari S. Possible green tea-induced thrombotic thrombocytopenic purpura. Am J Health Syst Pharm 2010;67:531-4.

We Would Love to Hear From You

This site uses Akismet to reduce spam. Learn how your comment data is processed.