Glass of milk before bed
“Here, have a glass of warm milk. That’ll help you sleep.”
That was what Mummy Pig suggested to either George or Peppa this morning. I’m not certain who, as I wasn’t watching it. My wee girl was, on the ‘iPad’ (actually an Android tablet, but she’s used to the term iPad from her older brother).
Anyhoo, whilst I think the show Peppa Pig is brilliant, that episode brought up a common misconception about drinking milk before bed.
The so-called ‘science’ behind it all is that milk contains tryptophan. This is an amino acid (one of many) that causes drowsiness in people. So if you can’t sleep, have a glass of milk. Some people say warm milk, but it’s the milk that is the key ingredient here. This is the same reason people get so tired after eating turkey (e.g. at Christmas or Thanksgiving) - the turkey is packed with tryptophan.
Except that - no. I mean, sure, there is tryptophan in turkey. And in milk. But this isn’t why people get sleepy.
Ah yes, the ol’ urban myth.
Is tryptophan beneficial for a good night’s sleep? Weeeeell… Maybe. The jury is still out on that one. What is certain, however, is that you’d have to eat a whole lot of turkey for it to have a noticeable effect, if indeed it had any effect. Ditto with milk. Plan to drink a few cow-loads of milk before bed? I didn’t think so.
For tryptophan to have any effect, it needs to get to the brain. That means getting through the blood-brain barrier. That’s tricky at the best of times (the brain-brain barrier is pretty picky in what it lets past) but even more so for tryptophan in the presence of other amino acids. So eating protein-rich foods (including milk) can actually decrease the ability of tryptophan to enter the brain. The trick is to eat foods high in carbohydrates, which stimulate the release of insulin. Insulin, in turn, makes it easier for tryptophan to enter the brain.
So let’s assume tryptophan makes it to your brain. Studies have shown that only one stage of sleep is enhanced by tryptophan – the first one when you’re falling asleep. Other aspects of sleep, such as the amount of deep sleep you get during the night, can actually be harmed by tryptophan.
So why, then, do you have a great night’s sleep after you have a glass of (warm) milk before bed? Yeah, that’s psychological. It’s a calming routine along the same lines as snuggling your favourite teddy bear...