The Debunker: Does Warm Milk Really Put You to Sleep?

by Ken Jennings

Dispelling all the misinformation in the world is a tough job when you’re up against the biggest liars of all: everyone’s parents. Let’s face it, Mom and Dad mean well, but parenting is a tough gig. In his new book Because I Said So!: The Truth Behind the Myths, Tales, and Warnings Every Generation Passes Down to Its Kids, Ken Jennings takes on generations of dubious parental wisdom on the dangers of gum-swallowing, knuckle-popping, post-meal swimming, and all the rest. And this month on Woot, Ken will be debunking four bonus parenting myths not found in his book. As we’ll see, Mother and Father don’t always know best.

Parental Myth #1: Drink Some Warm Milk Before Bed!

A glass of warm milk is an age-old folk remedy for insomnia. Mom’s bedtime advice got a nutritional boost in the 20th century when science discovered that milk is a good source for something called tryptophan, an amino acid sometimes prescribed as a sleep aid because the brain converts it into the sleep-regulating neurotransmitter melatonin.

warm milk

The problem is that, as we’ve seen in a past "Debunker" column, tryptophan doesn’t work as a sleep aid unless it’s taken on an empty stomach in dosages you’d never find in a glass of milk (or a serving of Thanksgiving turkey, or any of the other supposed tryptophan-rich foods sometimes recommended by Mom’s mental storehouse of 1970s-era Reader’s Digest articles). Milk is rich in protein, and a 2003 study at MIT found that protein inhibited the effects of tryptophan on the brain. Milk protein is also a good source of tyrosine, an amino acid often found in "mental alertness" supplements for its caffeine-like properties. And fully 60 percent of human adults are lactose intolerant, meaning that a bedtime glass of milk could lead to sleep-disturbing digestive problems for a majority of people worldwide. It’s quite possible that a glass of milk before bed could perk you up instead of settling you down.

Of course, any hot beverage after Jon Stewart (or, if you’re over forty, after Leno) will raise your body temperature and relax tense muscles. But the real reason why people swear by warm milk is probably psychological: the hot-milk routine soothes them, and they nod off because they think they will. But nutritionally speaking, a protein-rich snack like milk isn’t the way to go before bed. Instead, try an evening meal with a high glycemic index. Your blood sugar will spike and leave you feeling sluggish hours later when it’s time for bed. A big pasta dinner might not be great for your heart or your waistline, but you’ll sleep like a baby.

Quick Quiz: As fans of the movie A Christmas Story know, what brand of milk flavoring, often drunk warm, used to sponsor the Little Orphan Annie and Captain Midnight radio shows?

Ken Jennings is the author of Because I Said So!, Brainiac, Ken Jennings's Trivia Almanac, and Maphead. He's also the proud owner of an underwhelming Bag o' Crap. Follow him at or on Twitter as @KenJennings.

Photo by Flickr user avlxyz. Used under a Creative Commons License.