Tea is an infusion of flavorful leaves that has been consumed for centuries. The tea shrub (genus Camellia, family Theaceae) is a perennial evergreen with its natural habitat in the tropical and subtropical forests of the world. Cultivated varieties are widely grown in its home countries of South and South East Asia as well as parts of Africa and the Middle East. The young shoots or flushes are plucked and processed into green (unfermented), black (fermented) oolong (red, partially fermented) or yellow (partially fermented) teas. n fermented teas, the action of leaf oxidizing enzymes (mainly polyphenol oxidase) converts tannins and catechins in tea leaves into brown/red colored products1,5.
Catechin levels of Different Types of Tea1
| Green tea | 30-42 wt% |
| Oolong tea | 8-20 wt% |
| Black tea | 3-10 wt% |
| (Catechins are expressed as wt% of extract solids.) |
Green tea (Camellia sinensis) has been acclaimed for its medicinal properties which include:
- Antioxidant action on edible fats and oils,
- Antibacterial action against foodborne or phytopathogenic bacteria and infectious disease,
- Protection against tooth decay,
- Protection against atherosclerosis and hypertension, and
- antimutagenic effects.
Green tea’s therapeutic properties have been attributed to the antioxidant activities of the catechins, the active constituents of tea2. Tea catechins include (-)-epicatechin (EC), (-)-epicatechin gallate (ECg)(-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCg).4
A recent study3 focused on catechin intake and heart health. Dr. Ilja C.W.Arts and fellow researchers from the National Institute of Public Health and Environment (RIVM) in the Department of Chronic Diseases Epidemiolgy located in Bilthoven, Netherlands evaluated the association between high catechin intake (mainly from black tea, apples, and chocolate) and the incidence of mortality from ischemic heart disease and stroke. They used data from the Zutphen Elderly Study, a prospective cohort of 806 men aged 65-84 years old in 1985.
It was determined that elderly men who consumed the most catechins , were 51% less likely to develop ischemic heart disease over 10 years compared to men who consumed lesser amounts. (Ischemic heart disease is characterized by reduced amounts of oxygen and blood getting to heart due to narrowed arteries.)
The average catechin intake was 72 milligrams, and black tea was the major source of these compounds in the study. Although men who consumed more catechins also tended to exercise more, not smoke, drink less coffee, and consume more fiber and vitamin C, the research did not find these factors to influence the overall results3.
The mechanism by which catechins guard against certain diseases is not clear; however, Dr. Arts the study’s lead author, suggested they may work by preventing LDL ("bad") cholesterol from damaging cells by recycling other antioxidants (e.g. vitamin E) or by reducing the risk of inflammation associated with heart disease. More studies in other countries and populations should be conducted to confirm the results3.
>Sources:
- Graham, H.N. (1992) Prev. Med. 21, 334-350.
- Prophylactic functions of tea catechins : Information brochure, Food Research Laboratories, Mutsui Norin Co. Ltd., Japan.
- Reuters Health Report based on Arts et al. (2001) Am. J. Clin. Nutr. 74(2), 227-232.
- Chu, D.C. (1997) Green tea-its cultivation, processing of the leaves for drinking materials, and kinds of green tea,in Chemistry and applications of green Tea, Yamamato, T., Juneja, I.R., Chu, D.C. and Kim, M. eds.CRC Press LLC Boca Raton, FL.
- Bokuchava, M.A. and Skobeliva, N.J. (1980). Crit. Rev. Food Sci.& Nutr. 12, 303-370.
