Researchers Explain Why Warm Milk Makes You Tired

Researchers Explain Why Warm Milk Makes You Tired

warm milkHealth

People have been drinking warm milk at bedtime for centuries to induce sleep and relaxation. While some may call pass off the tradition as mere folklore, science proves its benefits.

Scientists previously believed that milk causes sleepiness due to its high concentration of tryptophan. This naturally occurring amino acid plays a vital role in producing serotonin, melatonin, niacin, and nicotinamide. It also helps maintain the body’s protein levels, muscles, and enzymes.

While it’s crucial for human development, scientists have recently found another compound in warm milk that promotes better sleep. A combination of milk peptides called casein tryptic hydrolysate (CTH) also acts as a natural sedative, relieving stress and promoting sleep. The study published in ACS’ Journal of Agricultural and Food Chemistry reveals specific peptides in CTH that could lead to improved sleep remedies.


According to the U.S. Centers for Disease Control and Prevention (CDC), around 33% of U.S. adults suffer from sleep deprivation. It’s recommended that adults get at least seven hours of sleep per night for optimal health. Adults who sleep less than seven hours per night have a higher risk of developing chronic conditions. These include diabetes, obesity, heart disease, stroke, high blood pressure, and mental health disorders.

Many doctors prescribe sedatives like benzodiazepines and zolpidem to patients who have insomnia. However, these types of medications are notorious for causing 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 typically have low GABA levels. In one study, people with insomnia had 30% lower GABA levels than those who slept well. Low GABA levels were also associated with more restless, disrupted sleep.

How Warm Milk Can Increase Sleepiness

warm milkSome scientists have called sleep deprivation plaguing the world an epidemic. With our modern, fast-paced lifestyles, artificial lighting, and separation from nature, it’s no wonder we can’t sleep very well. However, researchers believe they’ve found a solution in warm milk. The team for this study found several natural peptides, or proteins, that bind the GABA receptor. These proteins help ease anxiety and encourage better sleep.

For instance, treating a protein in cow’s milk – casein – with the digestive enzyme trypsin produces sleep-inducing peptides called CTH. In this mixture, they identified a particular peptide called α-casozepine (α-CZP) that could encourage sleepiness and relaxation. Lin Zheng, Mouming Zhao, and colleagues wondered if even more powerful sleep-enhancing peptides existed within CTH.

About the Study

So, to begin their study, the team compared the effects of CTH and α-CZP in sleeping mice. They found that CTH had better sleep-enhancing properties than α-CZP by itself. The findings suggested that other peptides besides α-CZP exist in CTH that promotes sleepiness.

Next, the team used mass spectrometry to find bioactive peptides released from CTH during simulated digestion. Then, they virtually screened these peptides for the ability to bind to the GABA receptor and cross the blood-brain barrier.

In screening the strongest peptide candidates in the mice, they discovered YPVEPF, which showed the most promise. The peptide helped 25% of mice fall asleep faster and increased their sleep duration by over 400%. Scientists say that additional peptides in CTH may exist that could promote better sleep through other pathways. Hopefully, they will continue their research to determine other peptides found in warm milk that enhance sleep.

The study was funded by the National Natural Science Foundation of China, the Guangdong Provincial Key R&D Program, the Shandong Provincial Key R&D Program, and the Specific Fund Program for Basic and Applied Basic Research of Guangdong Province.


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

Other Tips for Better Sleep

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

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