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Research on the Health Benefits of Caffeine in Tea

May 4, 2011 | By Beth Greenwood
Research on the Health Benefits of Caffeine in Tea
Photo Credit japan image by Andrey Kiselev from Fotolia.com

Pretty geishas, ceremonies and gardens --- the beverage known as tea has a long and interesting history. According to the University of Maryland, only water is consumed more frequently than tea; hundreds of millions of people around the world are tea drinkers. In addition to its use as a refreshing drink, there is evidence that tea, particularly green tea, has health benefits.

About Tea

Tea comes in three main varieties: green, black and oolong. All are derived from the leaves of the Camellia sinensis plant. The varieties are processed differently, and have different constituents as a result, although all contain caffeine. Green tea is unfermented; black and oolong teas are fermented, although most oolongs are only partially fermented. Fresh tea leaves contain compounds called catechins. When tea leaves are rolled during processing, the catechins ferment and become theaflavins and thearubiins. Other compounds include flavonols, theobromine and theophyllin.

Health Benefits of Tea

While caffeine is a component of tea, it is important to recognize that there is a difference between research specifically on caffeine and research on caffeinated tea. Other tea constituents may also have health benefits. According to the Linus Pauling Institute, drinking green or black tea provides protection from cardiovascular disease; and, green tea protects against stroke. Although there is some evidence that tea protects animals against cancer, the Linus Pauling Institute notes this effect has not been found in the research on humans. According to the Mayo Clinic, green tea reduces the risk of heart disease; reduces inflammation associated with Crohn's disease and ulcerative colitis and seems to protect the liver from damage from toxic substances such as alcohol. In addition, men who drink more than 10 cups of green tea per day are less likely to develop liver disorders.

Tea and Caffeine

The Linus Pauling Institute notes one clinical trial in which blood vessel dilation was affected by tea but an equivalent dose of plain caffeine had no effect, suggesting the effect was due to the tea rather than the caffeine in the tea. Another study, which did look specifically at the issue of caffeine in tea, was reported by Rachel Huxley in the 2009 issue of "Archives of Internal Medicine." Huxley noted that high intakes of caffeinated tea and coffee were associated with a reduced risk of diabetes. Decaffeinated tea, on the other hand, increased the risk of diabetes. A review published by G. Fagherazzi in "Public Health and Nutrition" in April 2011 found no relationship between coffee, tea or caffeine intake and breast cancer risk. Researchers in Japan, led by K. Tanaka, wrote in the April 2011 issue of "Parkinsonism and Related Disorders" that intake of black tea, Japanese and Chinese teas decreased the risk of Parkinson's disease. The researchers specifically noted that the correlation in this case seemed to be the caffeine, as caffeinated coffee had a similar effect.

Considerations and Warnings

While tea is widely consumed, it is not necessarily a harmless beverage. The Mayo Clinic recommends women who are pregnant or breastfeeding, people with heart problems, kidney disorders, stomach ulcers, and psychological disorders such as anxiety not drink tea. The clinic warns that excessive amounts of caffeine from any source, including tea, can cause irritability, insomnia, heart palpitations, and dizziness. Tea can also interact with some medications. Tea with caffeine can interact with benzodiazepines like valium; heart medications such as beta-blockers, Propranolol, and Metoprolol; and phenylpropanolamine, an ingredient in many over the counter cough medications. In addition, oral contraceptives may increase the stimulating effects of caffeinated tea. A few cups of tea a day is unlikely to cause any health problems and may have some benefits, but if you have any concerns or questions, you should discuss them with a health-care professional.

References

Article reviewed by GlennK Last updated on: May 4, 2011

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