Although milk has long served as remedy to restless nights, a new animal study published in the Journal of Medicinal Food has found that milk taken from cows during the evening may contain unique properties that make it especially good for treating anxiety and insomnia.

Having a warm glass of milk before bedtime is a tradition seen in cultures throughout the world, but many researchers say its sleep inducing properties are more psychological than science-based. The memory of mom giving milk at bedtime may be enough to induce sleepiness in some, for example. The new research, however, from Uimyung Research Institute for Neuroscience in South Korea, suggests milk harvested at night, may actually have sleep-inducing psychopharmacological properties.

The team discovered this after orally administering this night milk, as well as day milk, to mice at various concentrations. In addition to these mice, two other groups of control mice were given either an injection of diazepam, an anti-anxiety medication, or plain drinking water. The mice then went through a series of physical tests an hour after administration to determine their levels of activity.

Results revealed the mice that were administered diazepam were the least active, and most likely to lose balance and fall during the activity tests. Water-fed mice experienced the least trouble. Then, when it came to the milk groups, mice fed night milk fell nearly twice as much as mice fed the day milk when trying to complete the tasks — this suggested they were sleepier.

After the tasks, the animals administered night milk fell asleep faster and stayed asleep for longer. The researchers compared this effect as similar to that caused by diazepam. What's more, electroencephalograms (EEG) — a test used to measure brain waves and electrical activity in the brain — found night milk had no effect on brain wave activity. Diazepam, on the other hand, was found to induce abnormal brain wave activity, which the Wall Street Journal reported was reflective of the drug’s sedative-hypnotic properties.

The reasoning behind the night milk’s sleep-inducing properties may lie in its molecular makeup. According to the study, the night milk has an “exceptionally high amount” of tryptophan and melatonin than the day milk. Tryptophan is an amino acid commonly used to treat insomnia and anxiety, while melatonin is a hormone produced in the brain's pineal gland, which helps to control sleep and wake cycles.

While the subjects in this study were mice, past research on humans supports night milk’s sleep-inducing properties. Despite these potential benefits, harvesting night milk is a difficult matter. Most industrialized agriculture systems milk animals during the day. Even when they are milked in the evening, the milk is often mixed with milk produced during the daytime, The Guardian reported. Finally, even if you did go out searching for night-harvested milk, Gute Pillen – Schlechte Pillen (Good Pills, Bad Pills), a company that works to set the record straight on health claims, says you'd have to drink a lot of it to experience the sleep-inducing effects.

Source: de la Pena IJI, Eunyoung H, de la Pena JB, et al. Milk Collected at Night Induces Sedative and Anxiolytic-Like Effects and Augments Pentobarbital-Induced Sleeping Behavior in Mice. Journal of Medicinal Food. 2015