The growing evidence that caffeine consumption may help treat or prevent Alzheimer's disease has received an extra boost from two new studies.

Florida researchers report that a daily dose of 500 milligrams of caffeine - the equivalent found in five 8-ounce cups of coffee - reversed memory issues in mice bred to develop Alzheimer-like symptoms. After two months on the stimulant, the mice rebounded to score just as well on memory tests as normal mice of the same age that had never exhibited signs of dementia.

The studies, published in the July 5 online edition of the Journal of Alzheimer's Disease, also found that caffeine cut by half the mice's excessive blood and brain levels of beta amyloid, the protein linked to characteristic plaque found in human Alzheimer's disease.

"The new findings provide evidence that caffeine could be a viable 'treatment' for established Alzheimer's disease, and not simply a protective strategy," lead author Gary Arendash, a University of South Florida neuroscientist, said in a news release. "That's important because caffeine is a safe drug for most people, it easily enters the brain, and it appears to directly affect the disease process."

Past work at the Florida Alzheimer's Disease Research Center in Tampa, where these studies were done, found that caffeine in early adulthood appeared to prevent memory problems from occurring in these specially bred mice, possibly because of the stimulant's ability to calm the brain inflammation that causes beta amyloid levels to rise.

The research center also previously found that caffeine reduces beta amyloid levels in elderly people without dementia just as quickly as it does in the mice bred to have Alzheimer's symptoms.

Studies to test whether caffeine can help people with mild cognitive impairment or early Alzheimer's disease are likely to follow, investigator Huntington Potter, director of the Florida Alzheimer's Disease Research Center, said in the news release.

While consuming 500 milligrams of caffeine a day would not cause ill effects for most people, Arendash noted that people with high blood pressure or who are pregnant need to limit their caffeine intake. It is not known whether a smaller daily dose of caffeine would produce the same beneficial effects on the Alzheimer's mice.

In the most recent experiments, the researchers also found that caffeine did not improve the memory of normal mice as it did for the Alzheimer's mice. "This suggests that caffeine will not increase memory performance above normal levels. Rather, it appears to benefit those destined to develop Alzheimer's disease," Arendash said.