Thee tegen Alzheimer*

Het drinken van thee kan het geheugen stimuleren en zelfs de ontwikkeling van de ziekte van Alzheimer vertragen.

Volgens de onderzoekers van de universiteit van Newcastle remmen groene en zwarte thee de werking van het enzym acetylcholinesterase (ChE). Dat enzym breekt de stof acetylcholine af. Een tekort daaraan in de hersenen wordt in verband gebracht met de ziekte van Alzheimer. Beide soorten verhinderen ook de werking van het enzym butyrylcholinesterase, dat is aangetroffen in de hersenen van Alzheimer-patienten. Groene thee blijft volgens de wetenschappers een week werkzaam, zwarte thee een dag.

Drinking regular cups of tea could help improve your memory, research suggests.

A team from Newcastle University found green and black tea inhibited the activity of key enzymes in the brain associated with memory.

The researchers hope their findings, published in Phytotherapy Research, may lead to the development of a new treatment for Alzheimer's Disease.

They say tea appears to have the same effect as drugs specifically designed to combat the condition.

Alzheimer's disease is associated with a reduced level of a chemical called acetylcholine in the brain.

In lab tests, the Newcastle team found that both green and black tea inhibited the activity of the enzyme acetylcholinesterase (AChE), which breaks down this key chemical.

They also found both teas inhibited the activity of a second enzyme butyrylcholinesterase (BuChE), which has been discovered in protein deposits found in the brain of patients with Alzheimer's.

Green tea went one step further in that it obstructed the activity of beta-secretase, which plays a role in the production of protein deposits in the brain which are associated with Alzheimer's disease.

The scientists also found that it continued to have its inhibitive effect for a week, whereas black tea's enzyme-inhibiting properties lasted for only one day.

Drugs work same way

There is no cure for Alzheimer's but it is possible to slow the development of the disease.

Drugs currently on the market hinder the activity of AChE, and others are being developed which scientists hope will inhibit the activity of BuChE and beta-secretase.

However, many of the drugs currently available, such as donepezil, have unpleasant side effects and the medical profession is keen to find alternatives.

The Newcastle University researchers are now seeking funding to carry out further tests on green tea, which they hope will include clinical trials.

Their aim is to work towards the development of a medicinal tea which is specifically aimed at Alzheimer's sufferers.

The next step is to find out exactly which components of green tea inhibit the activity of the enzymes AChE, BuChE and beta-secretase.

Lead researcher Dr Ed Okello said: "Although there is no cure for Alzheimer's, tea could potentially be another weapon in the armoury which is used to treat this disease and slow down its development.

"It would be wonderful if our work could help improve the quality of life for millions of sufferers and their carers.

"Our findings are particularly exciting as tea is already a very popular drink, it is inexpensive, and there do not seem to be any adverse side effects when it is consumed.

"Still, we expect it will be several years until we are able to produce anything marketable."

Professor Clive Ballard, director of research, Alzheimer's Society, said: "This interesting research builds on previous evidence that suggests that green tea may be beneficial due to anti-oxidant properties.

"Certainly the effect on the cholinesterase enzyme (the target of current anti-dementia drugs such as Aricept) and beta-secretase (an enzyme which is important in the build up of plaques) is very exciting and requires further investigation."

Black tea - traditional English breakfast tea - is derived from the same plant as green tea, Camellia sinensis, but has a different taste and appearance because it is fermented (Nov. 2004).