MRI brain scans revealed that women who drank three cups of coffee per day (or 6 cups of tea) had lost less brain tissue called white matter than those who drank less. White matter, like buried phone lines, is a tangled mass of fiber-like connections deep in the brain that connect neurons in the surface layers into functional circuits. This tissue appears white because of the electrical insulation coating these fibers (myelin), which is essential for transmitting impulses. After the age of 50 our brain begins to lose white matter brain tissue, but coffee, according to this study, can check the loss. Only women drinking the equivalent of 3 or more cups of coffee per day were protected. There was no benefit from drinking less than two cups/day, and curiously, coffee had no protective effect for old men. Hormonal differences may be responsible, but the reason for the gender difference is not known.

The effects may be due to caffeine's ability to lessen the damaging effect of amyloid deposits in the aging brain, but caffeine also acts on the cells (called glia) that form myelin and it stimulates blood flow. Something to consider the next time you hear the question "Care for a second cup?"

Ritchie, K., et al.., (2010) Caffeine, Cognitive Function, and White Matter Lesions in the Elderly: Establishing Causality from Epidemiological Evidence. J. Alzheimer's Disease, Feb 17 on-line.