A reader writes:
How does the "sugar rush" work?
My kids go crazy when they get candy and soda (which they usually don't, but I'm not so cruel a mom as to feed them carrot sticks on their birthday), and on the rare occasions when I drink non-diet soda I get about 15 minutes of energy followed by a miserable crash... but now my doctor tells me that the sugar rush doesn't actually exist at all, so it's all in my head. And my kids' heads, too, apparently.
The doctor's not very tactful, but he's always seemed pretty sharp to me. Is he right?
Yes, your doctor is right. There's no such thing as a sugar rush. Sugar is not a stimulant, whether it's glucose, sucrose, the High-Fructose Corn Syrup that continues to rain stickily down on the entire population of North America, or any of the other sweet-tasting whatever-oses.
If you eat something with simple sugars in it that all pass into the bloodstream quickly - glucose, which doesn't need any digestion, being the simplest of all - you can end up messing with your body's sugar metabolism. Presuming you're not diabetic, your pancreas will pump out a lot of insulin to cope with the sugar bomb and then, when all of that sugar is quite suddenly dealt with, your body may find itself with an insulin surplus and give you a low-impact version of diabetic hypoglycemia. Lots of non-diabetic people have symptoms like this; it's even possible to feel the shaky, mind-fogged symptoms of mild hypoglycemia when your blood sugar and insulin levels are perfectly normal.
(The most important difference between "real" diabetic hypoglycemia and this pseudo-hypoglycemia is that the second version isn't dangerous. Just have a lie down, and in due course your body will drift back into homeostasis and you'll feel better. If a diabetic tries treating hypoglycemia that way, they can end up very ill, or dead.)
A transient hypoglycemic state does feel like a post-stimulant "crash", so there's solid basic biology behind that half of the "sugar rush" experience. There just isn't any actual rush at the start, unless you were hungry enough to feel faint when you ate that block of chocolate or drank that Humongous Gulp of fizzy sugar-water. And in that case, you again didn't get an actual rush, just a rapid return to normal function, which under the circumstances you could easily interpret as a rush.
(I'm ignoring, for the purposes of this discussion, the case of caffeinated drinks. Those certainly can give you some sort of "rush", followed by a crash, but it's not because of the sugar.)
So why do so many people swear that their kids go hyperactive when full of ultra-high-glycemic-index party food?
Well, it's partly because small children at birthday parties have a tendency to go nuts no matter what you feed them. And it's partly a placebo effect.
It doesn't seem as if it should be a placebo, though. If a child's had it drummed into them that they're expected to go hyperactive when they eat lollies, it wouldn't be terribly surprising if they did. But without such an expectation, sugar should have no particular placebo effect on the child.
But the placebo effect we're talking about here isn't happening to the child. It's happening to the adults who're observing the child. I don't know if there's been much research into this, but it's plausible for a couple of reasons. One is this study, which found that mothers who believed their young sons were "sugar sensitive" were more likely to perceive hyperactivity in their child if they're told the boy had been fed sugar, and less likely if they believed the boy had had an artificial sweetener, even though all of the children in the study actually got the artificial sweetener.
The second reason is that an analogous situation exists in veterinary medicine.
There are all sorts of nutty woo-woo alternative-medicine treatments available for animals, even openly preposterous activities like chiropractic adjustments for horses, performed by human beings with their bare hands. To actually shift the vertebrae of a horse around you'd need the assistance of the Incredible Hulk, or at least a very large mallet. But there the horse-chiros are, prodding and pushing and pretending something's moving (see also, "craniosacral therapy"...), and it's not hard to find horse owners who're convinced their animal's much healthier after the pantomime is complete.
So this is the placebo effect at one remove. The owner of the horse, or the parent of the child, can swear up and down that they see a clear difference, when one does not in fact exist.
(There can also be a direct placebo effect in veterinary medicine; an animal can be expected to change its behaviour if a strange person comes and messes with it, whether or not anything of real medical value is taking place. Animals are renowned for perking up when you take them to the vet, the usual explanation given being that they're in a scary environment and trying to look as strong and healthy as possible to avoid being selected for lunch by some unseen predator. This is a bit of a Just-So Story, though, because there's no way to prove it right or wrong until someone finds a talking dog. But never mind that for now.)
There are good reasons not to feed your kids a lot of sugar. But there's no reason to suppose, and several reasons to not suppose, that sugar has anything to do with hyperactivity.
And then commenters will, I hope, correct at least the most obvious flaws in my answer.