Sweet speed

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.

Psycho Science is a regular feature here. Ask me your science questions, and I'll answer them. Probably.

And then commenters will, I hope, correct at least the most obvious flaws in my answer.

13 Responses to “Sweet speed”

  1. jstanley0 Says:

    you've got a typo: "they're ion a scary environment"

  2. Anon Says:

    Wouldn't surprise me one bit if most of the hysteria over artificial flavours, colours and preservatives is like that as well.

  3. rndmnmbr Says:

    I seem to vaguely recall some study or something that basically stated kids didn't eat sugar and then get hyperactive, but instead got hyperactive then ate lots of sugar to fuel the state. Reversing the causation, if you were.

    To bad my recall is just vague enough that Google has no answers.

  4. Popup Says:

    Thank you!

    I've been trying to tell my wife that the glycemic index of white bread is in fact higher than that of most sweets, but nobody ever complained of kids on 'baguette high'.

    • Bern Says:

      Apparently the glycaemic index of carrots is higher than that of most sweets. It's all about the way it's defined.
      This website, for instance, says the GI of cooked carrots is 85, but the GI of a chocolate bar is only 70. I'm pretty sure I know which one is better for you to eat...

      The difference is that the carrot is less then 5% sugars, while the chocolate bar is going to be pretty high in both sugar and fat (a Mars bar is 63% sugar, and 17% fat).

      There's an interesting discussion of this in this episode of ABC Radio National's Health Report, from back in 2007. The gist there is that glycemic index isn't anywhere near as important as glycemic load, which is a measure of the total sugars you eat, rather than how fast your insulin system reacts to them (which is what glycemic index measures).
      BTW, that first site states that the glycemic index of white bread is 85, while the glycemic index of pure sugar is only 70. But, again, white bread contains a relatively low percentage of sugar. Well, unless you're buying it in the land of high-fructose-corn-syrup-added-to-everything... I couldn't stand the bread when I lived in the US. And everyone I spoke to there who'd been outside the US completely understood where I was coming from. :-D

      • Stark Says:

        Hey... you can get decent bread in US stores these days! Of course, Wonder Bread is still on the shelves too (it's a wonder alright... cause it sure as hell isn't bread).

        And yes... I've lived outside the US and I completely understand where you are coming from. I miss the neighborhood bakery half a block down from my old house in the Netherlands.... sigh... there's just nothing like it around here.

        I do have a pretty good Austrian pastry shop near me though... OK, I'm outta here - there's a Strudel with vanilla custard sauce calling me! (and no high fructose anything in sight)

  5. glaurung-quena Says:

    A factor you don't touch on is that sugar is often combined with psychoactive drugs like caffeine (in soda) or chocolate (in candy), which are stimulants.

    • Stark Says:

      While chocolate does technically have psycho-actives in it, it isn't exactly a high powered stimulant.

      It does contain relatively large amounts phenylethylamine (which is a known mood-elevating psychoactive) but, unfortunately for people looking to get their highs from chocolate, phenylethylamine is quickly broken down by digestion into far less interesting things. Blood tests typically show no increase in phenylethylamine in the blood of people who've recently eaten chocolate.

      Chocolate does also contain theobromine and caffeine -both of which are stimulants and work in much the same manner (specifically as adenosine receptor antagonists). They also are resistant to digestion. Typically though there is very little of these compounds actually in a serving of chocolate - though there are certainly caffeine added chocolates on the market.

      So, technically, chocolate does have psycho-actives in it but practically speaking you'd need to eat an awful lot to get any large effect (like "sugar rush") out of them.

      Many of the studies which have dis-proven the idea of a sugar rush did take into account the other ingredients involved in candies and sodas - and certainly if you are feeding a 5 year old a Bawls or Jolt Cola you will see a caffeine response. However candy itself, including typical chocolates fed to kids (ie, non-enhanced with extra caffeine) don't have any appreciable amounts of stimulants. It turns out that the entire "sugar rush" is attributable to parent expectation and the child's own excitement over getting something out of the ordinary which tastes so darned good.

      In studies where kids didn't know they were getting sugar there was no "sugar rush" observed at all.

      • Bern Says:

        So, technically, chocolate does have psycho-actives in it but practically speaking you'd need to eat an awful lot to get any large effect (like "sugar rush") out of them.

        For me, that means about three to four rows off a block of dark chocolate.
        I did that one evening while distracted by a rather good book, and stopped when I realised my heart was racing, I had the shakes, and I ended up not being able to get to sleep until sometime after 4am...

        • Stark Says:


          Of course it should be noted that dark chocolate typically does have notably more caffeine and theobromine than milk chocolate (which is typically what kids are having). You can think of milk chocolate as the decaf version of chocloate by comparison to a good dark chocolate. Sooo...next time forsake the goodness that is high cocoa content dark chocolate and eat some cheap ass nestle instead...

          Ya, I know, it's not the same ... ;)

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