The four-year study adds to the literature on tea's long-touted virtues. Moreover, any type of tea will do just fine.
The main finding is that tea slows down brain-cell degeneration and thus keeps the mind sharp into old age, said Professor Ng Tze Pin from the National University of Singapore's (NUS) psychological medicine department.
It was found that catechins, a natural compound in tea, protect brain cells from damaging protein build-up over the years, maintaining the brain's cognitive capability.
Moreover, the caffeine in tea, unlike that in coffee, contains the natural protein theanine, which counters the normal side effects of caffeine such as raised blood pressure, headaches and tiredness.
Brain-cell degeneration, caused by a combination of loss of nerve cells, predisposed genes, small strokes and increased levels of harmful protein build-up, often leads to dementia.
There is still no cure for it. An estimated 24 million people worldwide have some form of dementia, an illness that affects memory, thinking ability and behaviour.
In Singapore, about 5 per cent of those above age 65 and 13 per cent of those above 70 suffer from dementia. About 7,000 new cases are diagnosed every year and the number is expected to rise to 187,000 by 2052.
The NUS team studied the tea-drinking habits of 2,501 Chinese aged 55 and above, from September 2003 to December 2005.
The team members were Prof Ng, Prof Kua Ee Heok, Dr Feng Lei and Dr Niti Mathew, as well as Dr Yap Keng Bee from Alexandra Hospital's geriatric medicine department.
Participants' health, attention span, language use and visual and spatial abilities were assessed. Their tea consumption - how often, how much and what type - was monitored.
About 38 per cent did not drink tea. About 29 per cent drank only one kind of tea. The rest, about 33 per cent, drank a mix of teas.
Two-thirds of the tea drinkers maintained their scores on the same memory tests two years later.
Among the non-tea drinkers, 35 per cent saw a dip in their memory test scores by an average of two points, which signifies cognitive decline.
Age, education, level of physical activity and other drinks were taken into account.
Tea was the distinguishing factor keeping brain cells energised.
Said Prof Ng: 'Tea is cheap, non toxic and widely consumed.'
But tea alone cannot do the job. 'It still means a lifetime of good habits and a balanced diet,' he said.