Black, Green Tea May Slow Alzheimer's Disease
Adapted from WebMD Medical News, Oct. 27, 2004 A study from England's University of Newcastle upon Tyne shows that green and black teas may inhibit certain brain enzymes linked to Alzheimer's disease. The study's findings may lead to new therapeutic developments for dementia and Alzheimer's disease, which is estimated to affect 10 million people worldwide.
Coffee, in contrast, did not show any significant effects in the study.
Researchers including Edward Okello of the university's biology school compared green tea, black tea, and coffee. They found that tea stops the activity of chemicals in the brain associated with the development of Alzheimer's disease. Symptoms of Alzheimer's disease occur when brain nerve cells that process information and memory degenerate and die. Abnormalities such as plaque and protein 'tangles' form which form on nerve cells appear to play a role in Alzheimer's Disease.
One important brain chemicals, acetylcholinesterase (AchE), breaks down acetylcholine, one of the brain's most important chemical messengers that helps transport and process information. A drop in acetylcholine, in areas of the brain associated with memory and learning, has been linked to Alzheimer's disease. Medications used to treat Alzheimer's disease work by inhibiting acetylcholinesterase. Aricept, Exelon, and Reminyl are examples of these medications. In their research, the chemicals found in teas showed a similar ability to inhibit acetylcholinesterase, suggesting that daily consumption of tea might provide similar benefits as the most commonly proscribed Alzheimer's medications.
In the study teas also stopped the activity of other chemicals known to be key in making plaques and tangles in the brains of Alzheimer's patients. The second chemical is called butyrylcholinesterase (BuChE). However, green tea also inhibited a third and final brain chemical called beta-secretase, which is also involved in brain protein deposits seen with Alzheimer's disease.
Don't let that alphabet soup of chemical names throw you off. Green tea counteracted all three chemicals. Black tea was also powerful in curbing the first two chemicals, but only green tea inhibited beta-secretase. The researchers also found that green tea continued to have its inhibitive effect for a week, whereas black tea's enzyme-inhibiting properties lasted for only one day.
Black and green tea both come from the same plant, which goes by the Latin name of Camellia sinensis. Their antioxidant effects have been noted in various studies. The difference between the two drinks is that black tea has been fermented, resulting in a change in taste and appearance, and a possible reduction of antioxidant effects.
The researchers do not know exactly how to explain tea's effects demonstrated in their initial studies. In news reports, Okello says he knows of no evidence that Alzheimer's disease rates are lower in tea-drinking nations. Traditionally, green tea has been popular in Asian countries, while black tea is often associated with England.
The next step is identifying which key components in black and green tea might be producing the beneficial effects seen in the Okello study. Tea is not being proposed as the much-hoped-for cure for Alzheimer's disease; however, it might be directly useful or inspire new treatments to delay the disease if these findings are confirmed by more research.
Most tea drinkers are probably much more relaxed about preparing their tea than the researchers were. The scientists steeped the green tea for 45 minutes in freshly boiled water and prepared the black tea in boiled water for 30 minutes. The beverages were cooled to room temperature, centrifuged, and freeze-dried to capture every little detail. While not represented in this study, other studies have shown that more traditional steeping temperatures and times also produce a high concentration of water soluble polyphenols and antioxidants, including catechins, flavonoids and ECGC, so tea drinkers should not be concerned about overly steeping their favorite brews.
As for milk and sugar, they may be essential to many tea drinkers, but they were not included in this study, which was recently posted online by the journal Phytotherapy Research.
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