For generations, a warm glass of milk before bed has symbolized comfort."Drink this warm milk and sleep well"—starting the next day refreshed and energetic... Milk's sleep-promoting benefits have become common knowledge. But when insomnia strikes and you toss and turn, is warm milk really the answer? Hold on—does milk actually aid sleep? Our sleep channel has gathered two major "reasons" for milk's sleep-inducing effects. Whether these claims hold water? Read on to find out.
Does Milk Really Help You Sleep? Two Major "Reasons" for Milk's Sleep Benefits
(1) Milk aids sleep because it contains the "sleep-inducing" amino acid tryptophan
Some claim milk promotes restful sleep due to its L-tryptophan content. "Milk does indeed contain L-tryptophan, an amino acid found in the human body,"Lei Min, Deputy Director of the Nutrition Department at Hebei Medical University Third Hospital, explains that L-tryptophan helps produce sleep-inducing hormones—serotonin and melatonin. As a neurotransmitter, serotonin is primarily distributed in the pineal gland and hypothalamus, regulating physiological functions like pain perception, sleep, and body temperature.Melatonin, one of the hormones secreted by the pineal gland, shortens pre-sleep wakefulness and sleep onset time, improves sleep quality, and helps adjust to time zone changes.
However, the total amount of tryptophan in a small portion of food is insufficient to significantly alter hormone levels in the body. Furthermore, transporting tryptophan from milk to the brain may not be as straightforward as anticipated.
To protect the brain's vulnerability, the capillary structure in the brain prevents many blood-borne compounds from entering brain tissue—this is the blood-brain barrier. Any substance with sleep-inducing effects must first cross this barrier to reach the brain. L-tryptophan can indeed cross the blood-brain barrier, but research indicates:Milk is rich in various amino acids, including L-tryptophan. This protein-dense food causes a general increase in blood amino acid levels. These amino acids compete for passage through the blood-brain barrier, much like rush-hour subway entrances, which may actually reduce L-tryptophan's ability to cross.
Meat contains more sleep-promoting amino acids than milk
>Lei Min explains that L-tryptophan isn't exclusive to milk—it's found in many foods. For instance, tofu contains 1,119.9 mg/kg of L-tryptophan, while meat contains approximately 1,825.5 mg/kg—3.4 times and 5.6 times the amount in milk, respectively.Moreover, the total L-tryptophan in a single glass of milk is insufficient to significantly alter hormone levels, thus failing to provide the necessary effect for improving sleep. "Personally, I believe the L-tryptophan content in milk is inadequate to produce a noticeable calming effect."
(2) Warm milk accelerates sleep onset
"The perception that warm milk aids sleep likely stems from the warmth itself, which creates a soothing sensation conducive to falling asleep." While elevated skin temperature does accelerate sleep onset, a single glass of milk consumed won't significantly warm your skin. A warm bath proves far more effective.
Years of promotion have created a psychological association linking warm milk to better sleep for many.Sleep is influenced by multiple factors, with psychological issues playing a significant role. Professor Zhu Yulan, Director of the Epilepsy and Sleep Disorders Clinic at Harbin Medical University Second Hospital, notes that in outpatient settings, approximately 60% of insomnia cases stem from anxiety and mild depression. The positive psychological guidance that "warm milk aids sleep" can soothe nerves and facilitate falling asleep.
The Sleep Channel suggests that if one must seek "sleep-inducing foods," cookies are preferable to milk. Carbohydrates stimulate insulin synthesis, and insulin facilitates the entry of amino acids other than tryptophan into muscle tissue. With fewer competitors at the blood-brain barrier, more tryptophan reaches the brain, inducing drowsiness.
Two types of foods to avoid before bedtime that make falling asleep difficult:
1. Excessive consumption of spicy and stimulating foods, such as chili peppers, can excite the nerves, worsening neurasthenia and insomnia. Overindulging in hard-to-digest foods like fried items, fatty meats, glutinous rice, and sticky noodles prolongs their stay in the stomach, disrupting sleep.
2. Stimulating foods like alcohol, coffee, tea, and cocoa. These substances often have a dual effect: they initially excite the nervous system but can quickly trigger inhibition, leading to insomnia and accelerating the onset of nervous exhaustion.