Can a stroke victim consume moderate amounts of coffee? Is the nervous system affected by coffee?

Caffeine, the ingredient that gives coffee and many other beverages their jolt, is definitely a central-nervous-system stimulant. In addition to making the heart beat faster, it focuses the mind and improves performance on many mental tasks. It even increases the stamina of the body's muscles, allowing them to work longer and harder before exhaustion sets in.

In moderation, says UCLA neurologist Jeffrey L. Saver, caffeine intake is fine for patients who have suffered a stroke. But moderate is the key word here.

Past studies have shown that those with high caffeine intake — defined as five or more cups of coffee a day — are clearly at greater risk of hemorrhagic stroke, which is, essentially, bleeding inside the brain. The change in blood pressure that comes with high caffeine intake seems to increase the likelihood of bleeding into the brain, says Saver, an expert in stroke treatment.

If you've had one stroke, there's a higher-than-usual chance that you'll suffer a repeat stroke. So you want to cut your risks wherever you can.

Curiously, high caffeine intake isn't associated with greater risk of ischemic stroke, in which a clot obstructs the flow of blood to the brain. If you've had such a stroke and are pondering a fourth cup of java for the day, you'll have to let your judgment, rather than study results, be your guide.

In fact, a little caffeine may serve a useful function in a stroke patient's rehabilitation. Some studies have shown that a small dose of stimulant can prove helpful in learning that requires repetition and skill-building. Rehabilitation often involves relearning, through repetition, mental and physical skills that may have been compromised during a stroke. A little jolt of java may speed that process along, and make it a bit less tedious.

— Melissa Healy