A glass of milk before bed, says an old wives’ tale, brings a good night’s sleep. And it turns out that the drink might be even more effective if it was milked from a cow at night-time. That is the conclusion of study published in the Journal of Medicinal Food.
Milk is mostly water, but also includes chemicals that provide nutrition and act as a sleeping aid. Intriguingly, researchers from Sahmyook University in South Korea found that the amount of sleep-inducing and anxiety-lowering chemicals is greater if the cow is milked at night-time.
Compared with day-time milk, night-time milk contains 24% more tryptophan, which triggers the production of relaxation-inducing chemicals such as serotonin, and 10 times more melatonin, a chemical that regulates the body’s natural sleep-wake cycle.
The researchers tested the milk’s effects on mice. Each group of mice was fed one of four things: water, diazepam (a drug to treat anxiety), day-time milk, and night-time milk. The mice were then put on a rotating cylinder for 20 minutes—they had to keep walking in order not to fall off, so the drowsier mice wouldn’t fare as well as alert ones.
The mice fed water and day-time milk fell off twice, on average. Those fed night-time milk fell about five times and those fed diazepam fell as many as nine times. An hour after consuming it, the mice that consumed the night-time milk were significantly less active than those who consumed day-time milk.
The researchers didn’t perform the same test on humans (perhaps because finding people to jog on a rotating cylinder for 20 minutes in various states of drowsiness isn’t easy). Still, night-time cow milk may also give people the benefit of its sleep-inducing effects. And although this wasn’t tested either, it could be that a mother’s milk shows similar variations in chemicals based on the time of the day.