My own experience tells me that a glass of warm milk is a potent sedative. All it takes is a few ounces of heated dairy before my eye lids start getting real heavy.
It turns out, though, that warm milk is just a placebo. It works because I think it works.
According to age-old wisdom, milk is chock full of tryptophan, the sleep-inducing amino acid that is also well known for its presence in another food thought to have sedative effects, turkey.
But whether milk can induce sleep is debatable, and studies suggest that if it does, the effect has little to do with tryptophan.
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.
One study by researchers at the Massachusetts Institute of Technology demonstrated this in 2003. The study, which was published in The American Journal of Clinical Nutrition, showed that eating protein-rich foods -- like milk -- decreased the ability of tryptophan to enter the brain.
The trick, the study showed, 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 tryptophan can't explain the soporific effects of warm milk. But I'm thinking it may still explain why Thanksgiving turkey makes me sleepy, since by the time I reach for the turkey on my plate, my belly is already full of greasy carbs, which are being rapidly converted into insulin.
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My 10 month old baby doesn't like to go to sleep at night so we often give him a bottle of milk-based formula. Usually it is cold from the refrigerator, but on nights when he is particularly reluctant to sleep we heat the formula to body temperature. This, more consistently, gets him to relax and go to sleep.
I know it is anecdotal, but I'm unsure where the placebo effect might come in to play with a 10 month old baby. Are there studies that have examined when the placebo effect starts to be effective?
I seem to remember that the milk should be accompanied by biscuits to aid sleep - surely that would get the insulin going?
I usually have a couple big bowls of cereal right before bed, often after a short workout. My wife is in awe of my ability to lay down and fall asleep.
what does "placebo" mean in that context? If you have developed the pathways that insist on Warm Milk = Time to Sleep, that effect is very real...
Whether purely conditioned, or based on some real effect we still don't understand...is seems to me to go beyond what we typically called placebo.
Was Paulov's dog suffering from Placebo effect each time he salivated?
I always thought that milk helped people sleep because it is a base and calms upset stomachs. Who knew that placebos are the answer; how cool!
I've gotten pretty cynical about what "the latest survey suggests". If you feel sleepier after warm milk or turkey, then bonus for you!