Laboratory tests by a team at the University of Newcastle found that tea, and particularly green tea, inhibits the activity of the same enzymes in the brain currently targeted by drugs for Alzheimer's disease.
The researchers are hoping to develop a medicinal tea as an alternative treatment to slow memory loss in Alzheimer's sufferers, estimated to include around 10 million people worldwide, and rising.
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."
"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."
Dr Okello added that the findings suggested tea could boost the memory of everyday drinkers too.
The researchers from Newcastle University's Medicinal Plant Research Centre found both green and black tea inhibited the activity of the enzyme acetylcholinesterase (AChE), which breaks down the chemical messenger or neurotransmitter, acetylcholine. Alzheimer's is characterised by a drop in acetylcholine.
Green tea and black tea also hinder the activity of the enzyme butyrylcholinesterase (BuChE), which has been discovered in protein deposits found on 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 that are associated with Alzheimer's disease. 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.
Incidence of Alzheimer's disease is expected to rise fast with ageing populations but there is currently no cure. Drugs are available to slow the development of the disease by hindering the activity of AchE and others are being developed which scientists hope will inhibit the activity of BuChE and beta-secretase. But many of those currently available, such as donepezil, have unpleasant side effects and the medical profession is keen to find alternatives.
Professor Clive Ballard, director of research at the UK-based Alzheimer's Society, noted that the research builds on previous evidence that suggests that green tea may be beneficial due to antioxidant 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," he said.
The findings, published in the journal Phytotherapy Research (18, pp624-627), are the latest in a long line of results pointing to tea's disease-fighting potential. It is also being widely researched for its anti-cancer activity and benefits for heart health.
The Newcastle researchers are seeking funding to carry out further tests on green tea. They need to find out exactly which components of green tea inhibit the activity of the enzymes AChE, BuChE and beta-secretase.