One recent study comes from Finland where researchers followed about 1,400 coffee drinkers for more than two decades. Researchers found one group seemed to benefit the most: the people who'd been drinking three to five cups of coffee a day in their 40s and 50s.
"They had about a 65-to-70-percent reduced risk of developing Alzheimer's disease in their 70s," says Huntington Potter, a neurobiologist at the University of South Florida. Potters says effects held up even when researchers controlled for things such as cardiovascular disease, which can influence the risk of dementia.