The time of day the cow was milked could affect how much that nighttime glass actually helps you fall asleep.
That's because milk taken from the cow at night appears to contain more melatonin and tryptophan, a new study found. Researchers are calling it "night milk."
You know tryptophan — it's the compound in turkey and other food that's thought to make you sleepy. And melatonin is a natural hormone that regulates sleep.
These two compounds are found in day — aka "normal" — milk, but the authors of this study, led by Dr. Jae Hoon Cheong, of the Uimyung Research Institute for Neuroscience, found that night milk contained roughly 10 times the melatonin and around 24 percent more tryptophan.
Now, let's take a moment to note something important about this study: The night milk was tested in powdered form on mice and rats. That means these findings may not apply to humans.
Still, there's a company in New Zealand confident enough to market night milk, reports The New Zealand Herald.
There's no guarantee yet that the stuff works, but the tests Dr. Cheong and colleagues conducted were fairly compelling. They gave night milk to mice and compared their reactions to mice that received either water or a common anxiety drug.
The mice that received night milk showed decreased physical activity, balance and coordination — all hallmarks of an urgent need for some Zzzs — compared to the mice that only got water. The mice on the anxiety drug appeared sleepier than the ones that received night milk.
Another test Dr. Cheong and team conducted showed that brain waves — which regulate sleep cycles — didn't appear changed in rats that received night milk. That's a potential mark against night milk's effectiveness.
For now, you probably can't tell what time the cow responsible for your latest half gallon was milked — unless you're milking the cow yourself. If you're doing that, more power (and, hopefully, sleep) to you.
This study was published in the October issue of the Journal of Medicinal Food.
The Bio-Synergy Research Project, the Ministry of Science, ICT and Future Planning funded this research. The authors disclosed no conflicts of interest.