Steve February 23, 2021

My mum always told me that having a glass of warm milk before bed would help me sleep. So have many magazines, books, and websites. And, even some reputable medical publications.

If milk does help you sleep, and you regularly use it for that purpose, then, that’s great. Best not to jinx it by delving into the details too deeply, so you may wish to read something else instead of this report. If it works, stick with it and good luck to you.

But, if the old remedy has never worked for you, or you’re just curious, read on.

Does a glass of warm milk help you sleep or is the advice just an old piece of folklore?

Conventional wisdom maintains that the insomnia-beating benefits of milk are due to the amino acid tryptophan. Milk does contain tryptophan, and there is evidence that tryptophan can sometimes help people to get to sleep more quickly.

James Lake, MD notes in Psychology Today:

l-Tryptophan, 1 g, at bedtime reduces time to sleep onset in mild situational insomnia, and doses up to 15 g at bedtime may be necessary for severe insomnia. Case reports suggest that nighttime use of 5-HTP at 300 to 600 mg may improve mild to moderate insomnia and lessen sleep disturbances related to obstructive sleep apnea and narcolepsy.

Michael J. Breus, PhD notes on WebMD that:

Studies of tryptophan’s impact on sleep have found only one phase of sleep — the first one when you’re falling asleep — is enhanced by tryptophan. Other aspects of sleep, such as the amount of deep-sleep reached during the night, can be harmed by tryptophan, especially if it’s taken in supplemental form.

However, health experts have questioned the ability of tryptophan in milk to cross the blood-brain barrier.

Simon Young, Ph.D., a research psychologist at McGill University, notes in a 2016 Psychology Today article that “a glass of warm milk at bedtime will not raise the level of tryptophan entering your brain”.

Young discusses the claim that tryptophan in turkey can make you sleepy. He notes:

[…] tryptophan uses the same means of transport into the brain as other amino acids, and has to compete against them to cross the blood-brain barrier. As it happens, tryptophan is the least abundant amino acid. Forced to fight for access against the more common amino acids, it’s left waiting at the gate: the amount of tryptophan entering the brain decreases.

This blood-brain barrier factor applies to milk and many other foods containing tryptophan.

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A 2007 New York Times health report on the supposed benefits of warm milk as a sleep-aid, concurs, noting:

To have any soporific effect, tryptophan has to cross the blood-brain barrier. And in the presence of other amino acids, it ends up fighting — largely unsuccessfully — to move across.

And, a 2016 HuffPost report that discusses whether warm milk can help you sleep asked Central Queensland University sleep expert Drew Dawson for advice on the issue:

Despite milk’s tryptophan content, Dawson says the amount present in a glass of milk is lower than what would be contained in a melatonin supplement and that, for the average person, the dose is probably too low to feel the effects.

Given this evidence, it seems unlikely that tryptophan is the element in milk that helps you sleep.

Warm milk may simply provide a comfort connection that can help you drift off to sleep.

I have vivid childhood memories of my mum preparing warm chocolate milk and giving it to me in my “special cup” at bedtime. Just before my dad read me my nightly stories.

These are comforting memories that evoke feelings of safety, nurturing, and love. And, many people likely share such childhood memories.

So, it may be these pleasant thoughts and memories rather than the milk itself — or its temperature — that helps you relax and nod off at bedtime

And, of course, there is always the placebo effect. If you have been told from childhood that drinking warm milk helps you sleep and the idea has been reinforced over and over from many different sources in the years since then it may work for you for that reason alone.

In a discussion of the placebo effect, a Harvard Medical School report notes that:

Although you may have learned later in life that there isn’t much scientific evidence to support the practice [of drinking warm milk to help you sleep], you may still sleep better after a cup of warm milk at bedtime.

The ingrained belief that the remedy will work may be self-fulfilling. It works because you believe it will work.

There are many recommendations for sleep-inducing bedtime snacks.

Those who use them will often extoll their virtues and swear that they work. Some may have properties that likely do aid sleep. Many of the snacks probably work for the same psychological and placebo factors that I describe above.

But, the health expert consensus appears to be that, if you are going to partake of a bedtime snack, foods high in carbohydrates are probably a good choice.

Michael J. Breus notes:

The trick is to eat foods high in carbohydrates because the insulin released will make it easier for tryptophan to nudge itself into the brain. And for this very reason, I recommend combining an ample dose of carbohydrate together with a small amount of protein (which contains the amino acid tryptophan) as the ideal bedtime snack.

And, Woman’s Health writer Leah Fessler reports:

Researchers from Japan’s Yamaguchi University found that eating a carbohydrate-rich snack in the evening may help reset your circadian clock. Why carbs? In the study, researchers found that insulin influences the crucial sleep-regulating gene PER2 in mice; this led them to conclude that ingredients that promote insulin secretion might also help promote healthy circadian patterns in humans. And since carbs in particular increase insulin secretion, they should also help to regularize your body’s PER2 cycles so you’re drowsy when you should be.

I wish you good sleep and sweet dreams.

Man and Teddy Sleeping

Note: A version of this story was previously published by Brett Christensen on the blogging platform Medium.

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Brett Christensen

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