Briefs on Health Benefits of Tea

Health Benefits of Tea

John Kim, MD MPH & Jeanne Bowers published on the health benefits of tea in Alternative Therapy in Women's Health. Below is a brief containing important points.

Tea is a popular form of beverage made from the dried leaves of the plant Camellia sinensis. Popularity of tea consumption worldwide is second only to water. About three billion kilograms of tea are produced each year. Tea is cultivated in some 30 countries worldwide and is consumed globally. Black tea is consumed predominantly in Western and some Asian countries and green tea is consumed predominantly in China, Japan, India, and a number of countries in North Africa and the Middle East.

Tea originated in China 5000 years ago and was used as a medicine for various illnesses.
The tea was stored in the form of powder, leaves, and cakes. Traditional Chinese Medicine recommended drinking tea to healthy people as early as 200 BC. While people have been enjoying tea consumption more than 5000 years, the possible beneficial health effects of tea are being investigated only recently.

There are many types of tea, but they can be divided into two major groups: green tea and black tea. It is estimated that about 78% of tea produced worldwide is black tea while 20% is green tea, and 2% are oolong tea.

The health-beneficial chemical constituents are often collectively referred as flavonoids.
Initial epidemiological surveys have associated tea drinking with reduced risk of cardiovascular diseases (CVD) and cancer.

Cardiovascular Diseases
Many epidemiological studies have investigated the effects of tea consumption on cardiovascular disease. The results of several, but not all, of these studies are suggestive of a protective effect of black tea. These result showed that increase in tea consumption of three cups per day protected people from developing heart attacks by 11%.
One of the proposed mechanisms for the possible protective effect of tea against cardiovascular diseases is that tea polyphenols inhibit the oxidation of LDL, which is known to be involved in the development of atherosclerosis.

Another mechanism is hypocholesterolemic effect of tea providing another layer of protection from CVD. In animals fed diets high in fat and cholesterol, green tea, black tea and tea polyhenols prevented elevations in serum and liver lipids, decreased serum total cholesterol or atherogenic index, and increased fecal excretion of total lipids and cholesterol. When hamsters were fed a high fat diet, those drinking green tea or green tea polyphenols ha lower serum total cholesterol and higher fecal fat excretions than the control group.

Cancer
Health benefits of tea in cancer have been observed in epidemiologic studies. Studies show that a protective effect was associated between tea consumption and cancer of the colon, urinary bladder, stomach, esophagus, lung and pancreas. Most of the literature regarding tea consumption for prevention of cancer utilized green tea.

Polyphenols found in green tea have been shown to have potent antioxidant and antitumor effects. The most widely recognized properties of tea polyphenols are their antioxidant activities. Polyphenols bind to metal ions, preventing them from participating in peroxidase reactions. Green and black tea and isolated tea polyphenols have been shown to scavenge reactive oxygen and nitrogen species, reducing their damage to lipid membranes, proteins and nucleic acids in cell-free systems.

It should be noted that despite strong evidence suggesting a link between antioxidant activity an anticancer effects, regulatory organization have been cautious to allow any health claims linking intake of antioxidants to anticancer benefit. The U.S. Food and Drug Administration (FDA) has allowed a qualified health claim for antioxidant vitamins and cancer. The FDA concluded that despite the scientific evidence for anti-oxidant vitamins C and E may reduce the risk of certain forms of cancer, this evidence is limited and not conclusive.

Bone Density
A study of 1256 women in the U.K. reported that tea drinkers had significantly greater mean bone mineral density measurements independent of smoking status, the use of hormone therapy, coffee drinking, and whether milk was added to the tea. Authors concluded that drinking tea may help protect against osteoporosis in older women.