Does warm milk help you sleep?

Key takeaways

• Verdict: partly true. Warm milk has too little tryptophan to sedate you, though as part of a calm bedtime routine it may help you wind down.

• The tryptophan explanation doesn’t add up. A cup of milk has about 98 mg of tryptophan. Studies that found tryptophan helped sleep used 1 g or more, the amount in about 10 cups.

• Milk also works against its own tryptophan. It’s full of other amino acids that compete with tryptophan to get into the brain.

• The research on milk and sleep is thin. Reviews describe the benefits as limited and small, and the best-known positive trial is from 1972.

• If it’s part of your routine, keep it small. A big glass right before bed can mean a trip to the bathroom at night, and milk doesn’t suit people with lactose intolerance or reflux.

Where the warm milk idea comes from

A warm drink before bed is an old remedy, passed down long before anyone studied it. The scientific-sounding version came later. Milk contains tryptophan, an amino acid the body uses to make serotonin and then melatonin (the hormone that rises in the evening as you get sleepy). So the idea goes that milk delivers tryptophan, which becomes melatonin, which makes you sleepy.

Each step of that chain is real, but the amounts are far too small.

How much tryptophan is in a glass of milk?

Not much. According to the USDA’s food database, whole milk has about 0.04 g of tryptophan per 100 g, which works out to roughly 98 mg in a cup.

Compare that with the doses that seem to work. A 2022 review of tryptophan supplements found that people taking 1 g or more a day spent about 29 minutes awake after first falling asleep, against about 57 minutes for those taking less. It didn’t change how quickly they fell asleep or how long they slept in total. One gram is the tryptophan in about 10 cups of milk.

This is the same reason the Thanksgiving turkey story falls apart. Roast turkey meat has about 0.31 g of tryptophan per 100 g, while roast chicken has about 0.34 g, and nobody blames chicken for an afternoon nap. A big meal is a likelier culprit.

Why milk’s tryptophan doesn’t reach the brain easily

There’s a second problem. Tryptophan has to cross from the blood into the brain, and it competes for the same way in with several other amino acids. Milk is a protein food, so it brings plenty of those competitors along. In milk, tryptophan makes up only about 4% of that group of amino acids, which leaves it at a disadvantage.

Carbohydrates work the other way. They trigger insulin, which clears many of the competing amino acids out of the blood and gives tryptophan a better chance. In a 2003 study of nine people, a carbohydrate-rich breakfast raised the blood measure that predicts how much tryptophan reaches the brain, while a protein-rich breakfast lowered it.

The same idea shows up in sleep studies. In a 2007 study of 12 men, a high-glycemic rice meal eaten four hours before bed led to falling asleep in about 9 minutes, against 17.5 minutes after a low-glycemic one. In a small study, a purified, tryptophan-rich milk protein raised that brain-access measure by about 50%. Plain milk was not part of that study.

What studies of milk and sleep show

The direct evidence is small and mixed.

• The old positive trial. In a 1972 study, 18 people slept in a lab for 10 nights each, with and without a hot malted milk drink at bedtime. The older volunteers slept longer and woke less often after the drink. It was a malted milk-cereal drink, not plain milk.

• “Night milk.” Milk collected from cows at night contains more melatonin. In a 2005 Finnish study, older adults drinking night milk saw no clear improvement in sleep, and the season of the year had a bigger effect.

• Fermented milk. In a 2009 trial of 29 older adults, a fermented milk drink didn’t differ significantly from a placebo drink.

• The reviews. A 2020 review of 14 studies on dairy and sleep described the benefits as limited and small, and the night-milk findings as inconsistent. A 2025 analysis that pooled four studies found a small improvement in sleep quality scores.

In a large US survey, people who ate more dairy reported slightly fewer sleep problems, but that can’t show the dairy is the reason, and the study was part-funded by the dairy industry. The 2020 review was also funded by a dairy association.

Why warm milk might still help

If the chemistry doesn’t explain it, the ritual might. Having the same warm drink at the same time every night tells your body the day is ending. Bedtime routines are best studied in children. A 2018 review linked consistent bedtime routines to better sleep in young children, including falling asleep faster and waking less.

No study has compared warm milk with cold milk, and the only test against plain hot water was a small 1972 study of malted milk drinks, which found slightly fewer small movements during sleep. So there’s little evidence that the warmth or the milk itself is doing the work. A cup of caffeine-free herbal tea may do the same job. If you grew up with warm milk at bedtime, the comfort of a familiar habit is a reasonable explanation for why it feels like it helps.

When warm milk isn’t a good idea

• Lactose intolerance. Milk can cause bloating, gas, and stomach pain in people who don’t digest lactose well, which won’t help anyone sleep. Lactose-free milk is an option.

• Reflux. Lying down soon after eating or drinking can bring on heartburn. The NIDDK advises people with reflux to avoid eating for about three hours before lying down.

• Nighttime bathroom trips. Drinking a lot in the evening is a common cause of waking up to urinate. Keep the cup small and have it an hour or so before bed.

• Added sugar and chocolate. Hot chocolate brings a little caffeine along with the milk, and sweetened drinks add sugar. Plain milk, or milk with a little cinnamon or nutmeg, is the better choice.

What helps more than warm milk

Start with a regular wake-up time. The NHS advises people with insomnia to wake up and get out of bed at the same time every day, and to go to bed only when they feel sleepy. Watch the caffeine, too. Our post on how late you can drink coffee covers the cutoff.

Alcohol makes you drowsy but disrupts the second half of the night, as our post on alcohol and REM sleep explains. And in the small study above, a high-glycemic rice dinner four hours before bed helped people fall asleep faster.

Verdict: partly true

Warm milk does not work the way people usually say it does. A glass has a fraction of the tryptophan used in the studies, and milk’s other proteins crowd much of it out. Direct studies of milk and sleep are few, old, or small, and reviews call the benefits limited. But a warm drink can be a useful part of a calming routine, and routines do help sleep. If warm milk is part of yours and you feel fine afterward, there’s no reason to stop.

Frequently asked questions

Does warm milk really make you sleepy?

Not through tryptophan. A cup has about 98 mg, far less than the 1 g or more that helped sleep in studies. Any effect is more likely to come from the comfort and routine of a warm drink before bed.

Is warm milk better than cold milk for sleep?

There’s no evidence either way. No study has compared them. If warmth makes the drink more soothing for you, that’s a fine reason to heat it.

How long before bed should you drink warm milk?

About an hour before bed, and keep the cup small, so there’s time to use the bathroom before you lie down. If you get reflux, leave about three hours.

Does turkey make you sleepy because of tryptophan?

No. Turkey has a little less tryptophan than chicken, and neither has enough to make you drowsy. A big holiday meal, alcohol, and a late night may be likelier reasons for the post-dinner slump.

What can I drink instead of warm milk?

A caffeine-free herbal tea, such as chamomile, or a small glass of warm water works as a bedtime ritual too. Avoid caffeinated drinks, hot chocolate, and alcohol in the evening.

Does milk with honey help you sleep?

There’s no good evidence that it helps more than plain milk. A spoonful of honey adds a little carbohydrate, which in theory helps tryptophan reach the brain, but no study has looked at it.