Moderate coffee drinking—between 1 and 5 cups daily—may help reduce risk of dementia and Alzheimer’s disease, as well as Parkinson’s disease, studies suggest. How? Coffee’s antioxidants may prevent some damage to brain cells and boost the effects of neurotransmitters involved in cognitive function, say experts. Preliminary studies have noted that as coffee (or tea) intake rises, incidence of glioma, a form of brain cancer, tends to drop. Some researchers speculate that compounds in the brews could activate a DNA-repairing protein in cells—possibly preventing the DNA damage that can lead to cells becoming cancerous.