Drinking five cups of coffee a day could reverse memory problems seen in Alzheimer's disease, US scientists say.
The Florida research, carried out on mice, also suggested caffeine hampered the production of the protein plaques which are the hallmark of the disease. Previous research has also suggested a protective effect from caffeine. But British experts said the Journal of Alzheimer's disease study did not mean that dementia patients should start using caffeine supplements.
The 55 mice used in the University of South Florida study had been bred to develop symptoms of Alzheimer's disease.
First the researchers used behavioural tests to confirm the mice were exhibiting signs of memory impairment when they were aged 18 to 19 months, the equivalent to humans being about 70. Then they gave half the mice caffeine in their drinking water. The rest were given plain water.
The mice were given the equivalent of five 8 oz (227 grams) cups of coffee a day - about 500 milligrams of caffeine. The researchers say this is the same as is found in two cups of "specialty" coffees such as lattes or cappuccinos from coffee shops, 14 cups of tea, or 20 soft drinks.
When the mice were tested again after two months, those who were given the caffeine performed much better on tests measuring their memory and thinking skills and performed as well as mice of the same age without dementia.
Those drinking plain water continued to do poorly on the tests.