Recent data suggest that caffeine consumption up to 400 milligrams per day can help offset dementia.

The finding

What the evidence shows

Large observational studies do link moderate coffee and caffeine to lower dementia risk, often in a U shape with the lowest risk around 2 to 3 cups a day, roughly 300 mg. Those are associations among people who picked their own coffee habits, not proof that caffeine holds off dementia, and some big studies find no coffee effect while very heavy intake tracks with higher risk. The 400 mg figure is not a dementia number at all. It is the FDA's general safety guidance, an amount it describes as not generally associated with negative effects in healthy adults.