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Tea The Current State of Tea Research
Adapted from Linus Pauling Institute, June 2007
The sheer amount of scientific research on the health benefits of tea is increasing dramatically every year. There are a number of active researchers in many fields in the United States, Europe, China and Japan, and the quality and consistency of this research gets better every day.
Part of what makes scientific studies valuable is that they are generally conducted using rigorous methods, have undergone peer review, and the results of one study can be independently verified by being repeated by another researcher. It is also important to test the health benefits of tea in human beings rather than in animal studies or in the Petri dish, because the results do not always apply in human beings.
What is emerging are more studies conducted using human trials, with more specific research into the specific biological action of the dietary compounds found in tea.
The FDA Weighs In On Cancer and Cardiovascular Disease
One bellwether of how far the state of nutritional research on health, especially research on the health benefits of tea, has progresses is that last year the FDA adopted a conservative approach toward claims that green tea could protect against certain types of cancer, and has followed this with similar conclusions about supposed benefits for heart health.
"The FDA concludes that there is no credible evidence to support qualified health claims for green tea or green tea extract and a reduction of a number of risk factors associated with CVD," said the FDA letter.
The FDA letter was in response to a petition file in June 2005 by a major Japanese tea company and its U.S. subsidiary, seeking FDA support for their claim that that five ounces (150 mL) or more of green tea every day could reduce the risk of cardiovascular disease (CVD).
The FDA's acknowledgement that the current scientific evidence is 'supportive' rather than 'conclusive' is seen as a significant recognition of the growing number of peer-reviewed scientific studies demonstrating specific health benefits of teas in general, and green teas and the antioxidant EGCG in particular.
For example, in 1994 the Journal of the National Cancer Institute published the results of an epidemiological study indicating that drinking green tea reduced the risk of esophageal cancer in Chinese men and women by nearly sixty percent. In another example, University of Purdue researchers recently concluded that the compound EGCG found in in green tea inhibits the growth of cancer cells.
Additionally, the FDA did not close the door on reversing the claim in the future, stating "scientific information is subject to change, as are consumer consumption patterns. FDA intends to evaluate new information that becomes available to determine whether it necessitates a change in this decision. For example, scientific evidence may become available that will support the use of a qualified health claim or that will support significant scientific agreement."
Summary of Health Benefits of Tea
The antioxidant properties of tea are thought to have an effect against cancer by inhibiting formation of cancer causing substances. This is on of the most important and widely studied areas of the health benefits of tea. Tea consumption has long been tied to a lower risk of stomach, colon and breast cancer. Rutgers University researchers showed that a compound in black tea called TF-2 caused colorectal cancer cells to die, while leaving normal cells were unaffected. "The effect is quite dramatic." said a Rutgers professor Kuang Yu Chen, who speculates that the chemical might one day be made into an anti-cancer drug.
ImmunityPolyphenols have been shown to help increase the white blood cell count, which is responsible for fighting infection. The high vitamin C content found in green tea also contributes, as it is a well studied and accepted use in helping prevent and fight colds.
CardiovascularCardiovascular research suggest that a diet rich in the antioxidants found in tea is able to prevent heart disease and stoke. The tea constituents have been shown to stimulate the circulatory system, to strengthen the blood vessels and to decrease the cholesterol level in the blood stream.
DigestionEssential oils and polyphenols aid digestion by increasing the flow of digestive juices. Drinking tea during or after a high-cholesterol meal has been show to lower the increase in the fat content of the blood.
Body WeightGreen tea's antioxidant EGCG stimulates the body to burn calories, notably fat. In a Swiss study, a daily dose of 270mg EGCG (the amount in 2 to 3-5 cups of green tea) caused men to burn 4% more energy - about 80 extra calories a day. Green tea did not increase heart rate, and the calorie burning was not due to caffeine.
Teeth and BonesMany dentists recommend drinking tea because its rich in fluorides, a mineral that strengthens both tooth enamel and bones in fight against osteoporosis. The polyphenols in tea are shown to affect the bacteria in the mouth, thereby reducing the formation of plaque.
Germicide & AntibacterialTea has also been long known for neutralizing germs, including some that cause diarrhea, pneumonia, cholera, typhoid, dysentery cystitis, and skin infections. Its antibacterial properties help to inhibit certain throat infections.
Tames InflammationTea contains compounds that have long been known to reduce inflammation and help arthritis. TF-2, the newly discovered anti-cancer compound in black tea, has been found to suppress the Cox-2 gene that triggers inflammation. That's the same way the drugs Vioxx and Celebrex work. Also, in a UCLA study, drinking green tea was found to decrease the risk of chronic stomach inflammation, which can lead to cancer, by 50%