In brief

Could melatonin calm irritable bowels?

Melatonin is a lullaby in the form of a hormone. Doctors believe that we get sleepy most evenings partly because the pineal gland deep in the brain pumps out sleep-inducing melatonin when it gets dark.

It's not quite so simple: Study results have varied on how well melatonin works as a sleeping pill. Still, there's little question that the hormone influences the sleep-wake cycle (the so-called biological clock). Many people take it to cope with jet lag.