Milk’s Drowsy Effect

The claim: A glass of warm milk will help you sleep at night.

The facts: Few foods have a reputation for curing insomnia quite like warm milk.

It has long been known that milk is full of tryptophan, the sleep-inducing amino acid. tryptophan is also well known for being present in another food thought to have a sedative effect – turkey.

However, whether milk can induce sleep is debatable and studies suggest that if it does, the effect has little to do with tryptophan.

To have any soporific effect, tryptophen has to cross the blood-brain barrier. In the presence of other amino acids, it ends up fighting – largely unsuccessfully – to move across.

One study by researchers at the Massachusetts Institute of Technology demonstrated this in 2003. The study, which was published in The American Journal Of Clinical Nutrition, showed that eating protein-rich foods – like milk – decreased the ability of tryptophan to enter the brain.

The trick, the study showed, is to eat foods high in carbohydrates, which stimulate the release of insulin. Insulin, in turn makes it easier for troptophan to enter the brain.

However, surveys have found that many people swear by milk as a sleep aid and this may be psychological.

Scientists say the routine of drinking a glass of milk before bed can be as soothing as the feel of a favorite old blanket.

The bottom line: A glass of warm milk may make you drowsy, but this is not due to the effect of tryptophan.

- The New York Times