Two studies in the July 2009 issue of Journal of Alzheimer's Disease show that five cups of coffee a day reverse memory loss in mice with Alzheimer's disease.  The coffee also reduced blood and brain levels of beta-amyloid,the abnormal protein that may cause Alzheimer's disease in mice and people.

Other studies by the same researchers at the University of Florida show that caffeine lowers blood levels of beta-amyloid in elderly non-demented humans, and when given in early adulthood, prevents memory loss in mice bred to develop Alzheimer's disease in old age. Previous studies on rabbits also showed that caffeine may help to prevent Alzheimer's.

Researchers at the Florida Alzheimer's Disease Research Committee plan to start studies in humans to evaluate whether caffeine can prevent memory loss of early Alzheimer's disease. Other experiments by the same group show that caffeine may prevent memory loss by blocking the enzymes that make beta amyloid.

The amount of caffeine in two to five cups of coffee (200 to 500 milligrams) is probably safe, but more than five cups a day may cause insomnia, nervousness, irritability, nausea, anxiety, a fast or irregular heartbeat, headaches, breast pain or muscle tremors.

People who have high blood pressure or narrowed arteries leading to the heart may be advised to restrict caffeine. However, the Nurse's Study showed that heavy coffee drinking is not associated with increased risk for high blood pressure.  Unfiltered coffee raises blood levels of the bad LDL cholesterol and blood sugar levels after eating.  Pregnant women are advised to restrict caffeine since it may cause miscarriage or low birth weight.

Many studies show that caffeine can improve mood, alertness and energy, prevent diabetes, Parkinson's disease, and liver cancer, decrease the risk of stroke and may help prevent skin cancer.  It also increases endurance in athletes.