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Why does warm milk help you fall asleep better than cold milk?

--Ronald Duffy, Santa Fe, N.M.

There is no nutritional difference between warm and cold cow's milk--and both contain the amino acid tryptophan, which is known to have sedative effects. (That's why doctors often suggest dietary changes, including the consumption of cow's milk, to their insomniac patients.) Warm milk just has the added psychological benefit of being a comfort food. That being said, there's no sound scientific evidence that drinking milk--at any temperature--helps people fall asleep faster.