London: Milk collected from cows at night contains high amounts of tryptophan and melatonin, supplements proven to aid sleep and reduce anxiety, a new study has claimed.

The findings suggest that night milk might be an effective natural sleep aid for managing sleep-related disturbances and a promising alternative for the treatment of anxiety disorders.

Melatonin is a naturally occurring hormone which helps regulate the sleep and wake cycle, and tryptophan can be converted to serotonin and melatonin.

Researchers from Sahmyook University in Seoul, South Korea tested the effects on mice of milk collected at night.

The animals were given either night milk, day milk, water or diazepam, and then put on a rotating cylinder for 20 minutes.

The drowsier mice had a harder time staying on the cylinder, while the more alert ones fared better, 'The Telegraph' reported.

Researchers found that the mice given night milk fell off the cylinder more than twice as often as those given day milk or water - and an hour after consuming the night milk, they were significantly less active than those given day milk.

"Milk has long been known and used to promote sleep," the researchers said.

"The sleep-promoting effect of milk has been attributed to its psychological associations (ie, the memory of a mother giving milk at bedtime) and its rich store of sleep-promoting components.

The researchers said that the findings demonstrated that night milk is capable of producing sedative, anxiolytic, and sleep-promoting effects, comparable to those produced by the benzodiazepine and diazepam.

The research was published in the Journal of Medicinal Food.