You’ve probably heard your mother say it before, ‘a glass of warm milk before bed will knock you right out till the morning’. Drinking milk before bed for a good night’s sleep is something that many of us have probably done before without even questioning if it truly works, or if the belief that it will work is actually what helps lull us to sleep. So does milk make you sleepy?
In today’s article, we shall be looking further into the question ‘why does warm milk make you sleepy’? Is this tradition based in scientific fact or is it a myth that has somehow been ingrained into our culture.
Why Does Milk Make You Sleepy?
Insomnia and other sleep disorders/problems are quite common today.
In fact, according to a 2016 study, insomnia is one of the most common but neglected conditions that has both long term and serious effects on the health of a patient. This condition is so common that multiple studies have concluded that insomnia affects about 10 to 30 percent of the population worldwide – with some parts of the world showing insomnia cases in up to 50 and 60 percent of their population (9).
While the condition is most common in older adults, females, and people with medical and mental ill health, it can affect almost anyone and chronic insomnia can lead to significant challenges such as depression, impaired work performance, work- related/motor vehicle accidents, and overall poor quality of life (10).
According to a study by the Agency for Healthcare Research and Quality, insomnia is often treated with prescription medication such as ramelteon, doxepin, estazolam, temazepam, eszopiclone, etc. (14) melatonin receptor agonists, antidepressants, antipsychotics or via non‐medication treatments like cognitive behavioral therapy (10).
However, if your case of lack of sleep is not as bad, having a relaxing drink of milk before bed could work to help you calm down and drift off to sleep. But how does warm milk make you sleepy? Here are some research based facts of the matter.
It Is A Relaxing Drink
Yes, it is as simple as that. In the same way that a cup of coffee could make you hyperactive, a glass of warm milk is a soothing and relaxing drink that can help put you right to sleep. While scientists are not sure where these soothing side effects of milk come from, some have theorized some psychological reasons as to why:
It reminds us (subconsciously perhaps) of our mothers giving milk at bedtime (8) – During childhood, we all got a cup of warm milk before bedtime. While we may be adults now, the simple gesture of having this drink right before bed does not only soothe you but it also triggers your brain, signaling to it that it is time to sleep.
A combination of leisure-time physical activity and dairy promotes better sleep – One 2014 study done on 421 Japanese seniors showed that the older people who participated in some kind of leisure-time activity and consumed dairy products like milk, yogurt and cheese ended up finding it much easier to fall asleep at night (2).
Leisure time physical activities are those physical activities that are not required as essential activities of daily living and are performed at the discretion of the person. These include examples such as sports, exercising, gardening, and recreational walking.
Milk has sleep inducing properties
If you are wondering ‘why does tea with milk make you sleepy’, the answer lies in several chemical compounds that have been known to help induce sleep. According to Medicalnewstoday.com, these sleep-inducing compounds found in milk are tryptophan, calcium, vitamin D, and melatonin.
Melatonin is probably one of the most commonly known compounds that induce sleep. In human beings, this compound is found naturally in our bodies and is secreted by the pineal gland, which helps regulate the circadian rhythm (sleep and wake cycle).
This hormone is produced in its largest quantities at night and is among the things that helps us fall asleep and stay asleep. However, despite melatonin being a naturally occurring hormone, its levels gradually decrease with age which presents itself with impairment in the quality of sleep and other sleep disturbances (1, 7).
Luckily, milk can help increase your levels of melatonin making you sleep faster and better. According to various studies, milk produced/collected at night – aka ‘night milk’ -has higher levels of melatonin and can help children, adults, and even animals fall asleep (5, 3, 8).
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This is an essential amino acid, which like melatonin, is known to help boost sleep quality. When in the body tryptophan is converted to 5-hydroxytryptophan (the molecule 5-HTP) which then forms the hormone serotonin. Serotonin stabilizes our mood, feelings of well-being and relaxation which in turn helps with sleeping among other things (6).
Research done on rats has also shown that tryptophan is also converted into melatonin in the gastrointestinal tract. As we have seen above, this hormone has an incredibly large role in inducing sleep in human beings and animals alike (4).
Without enough tryptophan in the body, your melatonin and serotonin levels are likely to drop, which will not only interfere with your sleep, but could also lead to a higher risk of depression, Alzheimer’s, and abnormal aging (13).
According to medicalnewstoday.com, a study published by the European Neurology Journal showed that in the body, calcium levels are usually higher during some of the deepest levels of sleep, such as the REM phase. The study concluded by stating that problems such as the absence of REM deep sleep or disturbed REM sleep could be attributed to a calcium deficiency.
When it comes to this vitamin, it is often associated with its roles in promoting healthy bones and teeth, supporting immune, brain, and nervous system health, and more. However, one of the lesser known benefits of Vitamin D is in helping promote normal sleep and in preventing sleep disruption and daytime neurocognitive impairment (12, 11).
Why Does Milk And Turkey Make You Sleepy?
It’s all because of the compound tryptophan. Both milk and turkey are foods high in this compound as we have seen above tryptophan helps with the production of melatonin and serotonin, two hormones that promote relaxation and sleep.
The Bottom Line
If you are curious as to ‘why does milk make you sleepy’, scientists attribute this effect to both the psychological effects of drinking warm milk before bed during childhood and several sleep inducing compounds found in this relaxing drink. So, the next time you find it a little hard to sleep, get a warm glass of milk and wait to drift off to dreamland.
This article is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional advice or help and should not be relied on to make decisions of any kind. A licensed physician should be consulted for diagnosis and treatment of any medical conditions. Any action you take upon the information presented in this article is strictly at your own risk and responsibility!
- Age-related changes in melatonin levels in humans and its potential consequences for sleep disorders (1998, pubmed.ncbi.nlm.nih.gov)
- Association between difficulty initiating sleep in older adults and the combination of leisure-time physical activity and consumption of milk and milk products: a cross-sectional study (2014, pubmed.ncbi.nlm.nih.gov)
- Breastfeeding may improve nocturnal sleep and reduce infantile colic: potential role of breast milk melatonin (2012, pubmed.ncbi.nlm.nih.gov)
- Conversion L-tryptophan to melatonin in the gastrointestinal tract: the new high performance liquid chromatography method enabling simultaneous determination of six metabolites of L-tryptophan by native fluorescence and UV-VIS detection (2012, pubmed.ncbi.nlm.nih.gov)
- Effect of melatonin-rich night-time milk on sleep and activity in elderly institutionalized subjects (2005, pubmed.ncbi.nlm.nih.gov)
- L-Tryptophan: Basic Metabolic Functions, Behavioral Research and Therapeutic Indications (2009, ncbi.nlm.nih.gov)
- Melatonin: Nature’s most versatile biological signal? (2006, pubmed.ncbi.nlm.nih.gov)
- Milk Collected at Night Induces Sedative and Anxiolytic-Like Effects and Augments Pentobarbital-Induced Sleeping Behavior in Mice (2015, pubmed.ncbi.nlm.nih.gov)
- Prevalence of chronic insomnia in adult patients and its correlation with medical comorbidities (2016, ncbi.nlm.nih.gov)
- The assessment and management of insomnia: an update (2019, ncbi.nlm.nih.gov)
- The Association between Vitamin D Deficiency and Sleep Disorders: A Systematic Review and Meta-Analysis (2018, ncbi.nlm.nih.gov)
- The link between vitamin D metabolism and sleep medicine (2014, pubmed.ncbi.nlm.nih.gov)
- The therapeutic potential for tryptophan and melatonin: possible roles in depression, sleep, Alzheimer’s disease and abnormal aging (1990, pubmed.ncbi.nlm.nih.gov)
- Treatment of Insomnia Disorder (2014, effectivehealthcare.ahrq.gov)