Study explains why warm milk induces sleep

People have been drinking warm milk before bed for centuries to induce sleep and relaxation. While some might call the passage from tradition to mere folklore, science shows its benefits.

Scientists previously believed that milk causes drowsiness due to its high concentration of tryptophan. This natural amino acid plays a vital role in the production of serotonin, melatonin, niacin and nicotinamide. It also helps maintain the body’s protein, muscle and enzyme levels.

While crucial to human development, scientists have recently discovered another compound in warm milk that promotes better sleep. A combination of milk peptides called tryptic casein hydrolyzate (CTH) also acts as a natural sedative, relieving stress and promoting sleep. The study published in Journal of Agricultural and Food Chemistry of ACS reveals specific peptides on HTCs that may lead to better sleeping pills.

According to Centers for Disease Control and Prevention (CDC ) of the US, about 33% of North American adults suffer from sleep deprivation. It is recommended that adults sleep at least seven hours a night for optimal health. Adults who sleep less than seven hours a night are at increased risk of developing chronic illnesses. This includes diabetes, obesity, heart disease, stroke, high blood pressure and mental health disorders.

Many doctors prescribe sedatives such as benzodiazepines and zolpidem for patients with insomnia. However, these types of drugs are known to cause unwanted side effects and even addiction. Sedatives work by activating GABA receptors in the brain, which are proteins that inhibit nerve signaling.

Scientists have found that people with insomnia tend to have low levels of GABA. On a study , people with insomnia had 30% lower GABA levels than those who slept well. Low GABA levels were also associated with more restless and disrupted sleep.


Some scientists consider sleep deprivation around the world an epidemic. With our fast-paced, modern lifestyle, artificial lighting and separation from nature, it’s no wonder we can’t sleep very well. However, researchers believe they found a solution in warm milk. The team in this study found several natural peptides or proteins that bind to the GABA receptor. These proteins help relieve anxiety and promote better sleep.

For example, treating a cow’s milk protein, casein, with the digestive enzyme trypsin produces sleep-inducing peptides called CTH. In this mixture, they identified a specific peptide called α-Casozepine (α-CZP) that can stimulate sleepiness and relaxation. Lin Zheng, Mouming Zhao and their colleagues wondered if there were even more powerful sleep-enhancing peptides inside HTC.


So, to begin their study, the team compared the effects of CTH and α-CZP in sleeping rats. They found that HTC had better sleep-enhancing properties than α-CZP alone. The findings suggested that there are other peptides besides α-CZP on HTC that promote drowsiness.

The team then used mass spectrometry to find bioactive peptides released from the CTH during simulated digestion. They then virtually examined these peptides for their ability to bind to the GABA receptor and cross the blood-brain barrier.

By selecting the strongest peptide candidates in mice, they found YPVEPF, which turned out to be the most promising. The peptide helped 25% of mice fall asleep faster and increased sleep duration by more than 400%. Scientists say there may be additional peptides on HTC that could promote better sleep in other ways. Hopefully, they will continue their research to determine other sleep-enhancing peptides found in warm milk.

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The study was funded by the National Natural Science Foundation of China, the Key Research and Development Program of Guangdong Province, the Key Research and Development Program of Shandong Province and the Specific Funds Program for Basic and Applied Basic Research of the Province of Guangdong.

Other scientific studies show that warm milk can help increase sleepiness at bedtime. In a study of patients in a hospital cardiac unit, those who drank warm milk and honey for three days had improved sleep. From others study which included adults over age 60 found that drinking warm fermented milk for three weeks reduced wakefulness.


The CDC lists other recommendations for getting better quality sleep each night:

  • Maintain a consistent sleep schedule. Have regular bedtime and waking hours, even on weekends, to restore your circadian rhythm.
  • Keep your bedroom quiet, dark and cool at night to help induce sleep.
  • Remove electronic devices like televisions, computers and telephones from your sleeping space. Also, make sure you turn off the appliances at least a few hours before going to bed. Blue light emitted by electronics can stop melatonin production.
  • Don’t eat big meals before going to bed; if you’re hungry, grab a protein-rich snack like peanut butter or a piece of cheese. Also, avoid caffeine and alcohol before bed.
  • You must exercise every day. Even if you walk for 30 minutes, moving your body a little every day promotes better sleep.


  • Cheese
  • Turkey
  • Fish
  • Sunflower seeds
  • pumpkin seeds

Hopefully, these tips will help you get more sleep each night. Remember to prioritize your sleep because it’s essential to your health and well-being. Globally, citizens have reported an increase in sleep deprivation over the years and experts recognize the problem as a public health issue.

Fortunately, a better night’s sleep often comes down to modifiable factors such as sleep hygiene. Make sure you have a bedtime relaxation routine to prepare your body and mind for sleep.


For generations, cultures across the world have turned to warm milk to promote better sleep. Scientists now have evidence to show that it’s not just folklore: peptides in milk bind to GABA receptors to stimulate sleep. The findings showed that two peptides in particular, α-CZP and YPVEPF, had sleep-enhancing effects.

The researchers hope to conduct additional studies in the future to identify other peptides in warm milk that promote sleep. For now, this study may help develop natural sleep remedies in the future.

By Kristen Lawrence. Article in English

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