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Why Does Warm Milk Make You Sleepy?

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An estimated 60 million Americans have a sleeping disorder, and we’ll go to great lengths and try some odd tricks to get a night of quality sleep. From ASMR to eyemasks, to blackout curtains, to sleeping pills, we have an abundance of options catered to optimize our periods of rest.
Despite the various choices to help us get some shuteye, you may have a great option already hiding inside your refrigerator. We’ve heard stories of warm milk being a lifesaver for many people, so we decided to do some research and find out exactly why warm milk helps you sleep.

Does Warm Milk Help You Sleep?

For years, we’ve been told that if we’re having trouble falling asleep, we should drink a glass of warm milk. Upon researching whether or not this was legitimate or an urban legend, we discovered that it’s a bit of both. Milk is loaded with an amino acid called tryptophan, which most people associate with turkey, and sleeping.
However, when comparing by volume, whole milk has much more tryptophan than any other food.

What’s the Scientific Basis?

While part of what makes milk helpful for sleep is rooted in science, part of the theory about this warm beverage being sleep-inducing may also be psychological, but that doesn’t make it any less valid. The brain is a powerful tool, so even if something exists in our minds, that doesn’t necessarily make it less real.
For some people who grew up with parents who gave them warm milk before bed, this routine is a recognizable signal that it’s time for bed. By following this habit, you become sleepy on auto-pilot.
Beyond the signaling effects of the routine making you drowsy, the act of stopping and engaging in a relaxing activity with a determined purpose to help you doze can help your brain wind down and prepare for bed. It makes sense that it’s easier to fall asleep after drinking a warm and soothing beverage lounging on the sofa than it is to nod off after watching a violent television show and going straight to bed.
However, despite the psychological effects of warm milk, there is evidence rooted in scientific facts about tryptophan’s impact on our sleepiness, so we’ll address those ideas and put them into perspective below.

What is Tryptophan?

Upon hearing the term tryptophan, some may think of eating a metric ton of turkey on Thanksgiving and then going straight to sleep. However, tryptophan is an essential amino acid that we need to have in our diets for various purposes.
Tryptophan is an essential factor in the production of serotonin in humans. Further, the amino acid plays a critical role in healthy brain function and quality sleep.
As humans, we don’t produce it in our bodies, so we have to eat it to access the ingredient. Fortunately for us, it’s common in a lot of everyday foods. Tryptophan is linked to sleep because this ingredient is the precursor for serotonin, a hormone that significantly affects our mood and ability to sleep. Serotonin gets converted to melatonin, and that’s what helps us sleep.
There is a trick to prompt tryptophan to enter the brain. Combining carbohydrates with dairy or tryptophan should increase your insulin levels, making it easier for tryptophan to get to your brain.

How Tryptophan is Linked to Serotonin

Thanksgiving is often associated with “food coma,” or otherwise feeling sleepy after a large meal, and there’s a reason for this phenomenon. With turkey being a large portion of this tradition, people often consume about 300 to 400 grams of protein on this day, and it’s typically paired with a significant amount of carbohydrates.[1]
When people gobble down this combination, their blood sugar typically increases, stimulating the production of insulin, which paves the way for tryptophan to make it’s way from our veins to the brain.
The amino acid is necessary for the production of serotonin, a chemical that plays a significant role in our mental well-being. Tryptophan is also directly related to the production of melatonin, letting us sleep with ease.
Extensive research has shown how serotonin is linked to poor mood, mental health disorders, and plays a critical role in depression. Further, low levels of serotonin may cause memory issues. Individuals who have struggled with depression in the past are also more likely to be affected by low levels of the hormone when compared to those who have no history of the illness.[2]

Other Foods with Tryptophan

Turkey is often thought of as a sleep-inducer, but chicken, nuts, soy beans, beef, and many other items also contain similar amounts.


Chicken, especially stewing meat, is even higher in tryptophan than turkey. Goose, and other lean sources of poultry are often high in protein and lower in fat. Dark meat in chicken typically contains more than light meat.


While oatmeal doesn’t contain nearly as much tryptophan as milk, it does have 147 milligrams per cup, making it a great source of the amino acid.


Beans and lentils contain up to 70% of the recommended daily allowance (RDI) of tryptophan, depending on the variety. Further, soybeans often get a bad reputation for not being as high a source of protein. However, soybeans contain an abundance of nutrients, including tryptophan.


Seeds like pumpkin, chia, sesame, sunflower, and flax are excellent sources. The top nuts to consume are pistachios, cashews, almonds, and hazelnuts.


Potatoes don’t contain tryptophan, but they help spike your body’s insulin, which allows the tryptophan-rich foods to enter your bloodstream. The same concept that applies to potatoes also applies to pasta.


Canned tuna contains a whopping 472 milligrams of tryptophan per ounce, and excellent source for good sleep and a good mood.


Turkey is the most famous member of the tryptophan family, although not all turkey parts contain the same amount of this amino acid, and it’s also not the food that has the most. Here’s the order of tryptophan-containing body parts from highest to lowest:

  1. Wing
  2. Breast
  3. Drumstick

What Type of Milk is Best?

Whole milk is often shunned as less nutritious or calorically dense. However, while the calorie part may be true, it’s also full of healthy nutrients to fuel our bodies.
Further, the temperature is not nearly as important as the fat content. Milk higher in fat (whole vs. skim, for example) will induce your body to produce more tryptophan and potentially aid in sleep. Whole milk contains 551 milligrams of tryptophan per quart.

Benefits of Drinking Warm Milk

Milk is high in protein, so if you’re looking for an easy way to add protein to your diet, this is an easy way to boost your protein intake. If you opt for skim varieties, you can also cut your fat intake.
Some of us as kids may remember being told to drink plenty of milk to grow up to be tall and strong. While that may not be true exactly, it does provide you with some essential nutrients other than those mentioned above. Milk contains critical nutrients like calcium, potassium, iodine, Vitamin B2 and B12, and phosphorous.
According to a participant in a study on milk’s effect on sleep, upon “drinking a cup of warm milk every night before hitting the sheetings, [she fell] asleep quickly when compared to before” when she didn’t drink milk at all.[3]

Frequently Asked Questions

Does it help people with insomnia?

People suffer from insomnia for a variety of reasons, but some of the more common culprits are stress and anxiety. Because the routine of relaxing to drink a warm beverage at the end of the day can help ease these feelings, it’s a logical conclusion that drinking a glass of milk before bed can potentially help with insomnia.
Read More: Best Mattresses for Insomnia

What is melatonin?

Melatonin is a hormone that’s linked to our biological clock and is known for helping us sleep. During the day, it drops drastically, especially in the presence of light. At night, melatonin returns to induce sleepiness.
If you suffer from a sleep disorder, keep in mind that any exposure to light in the middle of the night, even just flipping the switch for a minute in the bathroom, will disrupt your body’s melatonin production and negatively impact your sleep.
For More Information: Best Melatonin Supplement

What’s the difference between drinking warm and cold milk?

People who are lactose intolerant may have an easier time consuming warm dairy rather than cold. It turns out that heat breaks down the lactose, making it easier to digest. Cold milk can benefit people who suffer from acid reflux. It’s also effective in combatting dehydration, but then again, so is water.

Can I put honey in it?

Putting honey in your dairy beverage can help provide additional benefits. When these two delicious substances combine, they help with your digestion and can alleviate constipation. There’s also evidence that adding honey helps your skin achieve a healthy glow. That’s probably why you see so many body washes and spa products with “milk and honey” formulas.

Rachael Gilpin

Rachael Gilpin

Content Writer

About Author

Rachael is a content writer for Sleep Advisor who loves combining her enthusiasm for writing and wellness.

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