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Do you think that sugar makes kids hyper? Well, you're wrong. Yes, WRONG. How do we know? Randomized controlled trials.

RCTs are pretty much the most robust study design there is, and also the only way to prove causality. This week's episode of Healthcare Triage explains how randomized controlled trials work, and why they are superior to other types of studies. It also explains how they've been used to prove, without a doubt, that sugar doesn't make kids hyper. Don't believe it? Watch the video and argue with us in the comments below if you're still not convinced.

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Read more on Aaron's blog:

Link to a meta-analysis of many of the studies discussed here:

John Green -- Executive Producer
Stan Muller -- Director, Producer
Aaron Carroll -- Writer
Mark Olsen - Graphics
You can't turn on the news these days without finding out that something else is bad for you. Cell phones will give you cancer. Artificial sweeteners will kill you. Eating at night will make you fat. Video games will make you violent. Reading in the dark will make you blind. It's a wonder the species hasn't died out already.

But in almost none of these cases, has anyone ever proven that something causes something else. To do that, you need a specific and certain type of study. You need a Randomized Control Trial or RCT. But RCTs are the hardest and often most expensive kind of studies to do. Nonetheless, they are necessary to prove a causal link between one thing and another. And they're the topic of this week's Healthcare Triage.


I've written a number of books about medical myths. And the one that still causes me the most heartache and gets me the most hate tweets is the myth that sugar makes kids hyper. I can already hear some of you screaming. You now think I'm crazy or that I'm in pocket of Big Sugar. You've seen it for yourself, you or your kid gets hyper when you, he, or she eats sugar. But what you're describing isn't a study, it's an anecdote. I don't care that you've seen it lots of times. The plural of anecdote is not data. So what do we need to do to prove that sugar makes kids hyper?

First, we might get a bunch of kids together and give them candy. We'd see if they acted hyper after they ate it. Let's say they did, would that prove anything? NO! They might've been hyper already or maybe they all got more and more tired over the hours and hours we forced them to eat candy and that's what made them hyper. You can't tell if it was the sugar or if it was something else unrelated to that, that led to their hyper behavior.

So another thing we could do is take a different set of kids and not give them candy. Then we could compare their behavior to the kids who got candy. And as long as we kept everything else the same, like the time of day, we can be more sure that it's the candy that had an effect. The kids that didn't get the candy comprise what is called a Control Group. And this study design would be a Controlled Trial.

But these's another potential problem. Maybe the kids in the first group were all boys. Maybe the second group was all girls and that might mean that the differences we see might not be because of the candy, but because girls are made of sugar and spice and boys are made of snails and puppy dog's tails. To overcome this type of bias, we can't let the parents make the decision of which kids go in each group. We have to make it random. If we take all the kids and randomly assign them to candy or no candy, then we can be even more sure that whatever effect we saw was because of the sugar. This is a Randomized Control Trial.

It's still not perfect though. Maybe the kids who got the candy loved the sweet, sweet taste of sugar so much that they acted differently just out of happiness. Maybe the kids who got no candy were so pissed that they just sat and sulked. Then the difference wouldn't be because of the sugar, it would just be because of the taste.  Or maybe the parents who saw their kids get sugar just believed that their kids were more hyper. They may want to prove me wrong so badly that they convinced themselves that they saw hyperactivity even when it wasn't there.

To overcome these biases, we have to prevent the kids, who are the subjects, from knowing whether they are in the sugar or no sugar group. We also have to prevent the parents, or the observers, from knowing that too. So first, we have to come up with a placebo, or fake treatment. Say, sugar-free candy.  Bleh! But if the kids can't tell which is which, then we've blinded them  to which group they're in. If the observers also don't know which group the kids are in, this would be a Double-Blinded Randomized Placebo Controlled Trial. That's a mouthful, but it's  pretty much the most robust study design you can have.

This is a subtle, but incredibly important thing.  Other study designs can prove an association, or a correlation, but as Hank and John and anyone who thinks scientifically like to say: "Correlation is not causation".  We may know that television viewing is correlated with Attention Deficit Hyperactivity Disorder, but is that because TV causes ADHD, or is it because kids with ADHD like to watch more TV?  Or is something else to blame?  Could it be the parents of kids with ADHD are more permissive of TV watching?  We just don't know!  Only a randomized controlled trial can prove causality.  

Now, you can't have a randomized controlled trial for everything.  We're never gonna have one that proves that breastfeeding is superior to bottle feeding, because it wouldn't be ethical to force women to do one or the other.  We'll never have a randomized controlled trial of smoking and cancer, because it wouldn't be right to force people to smoke.  We're too sure it's probably really bad for you.  That, by the way, is how the tobacco companies get away with saying that it's never been proven that smoking causes cancer.  'Cause there's never been a randomized controlled trial.  And there never will be.  Back to sugar and kids!

There have been 12, count them, 12 randomized controlled trials of sugar and hyper-active behavior in kids.  They've been published in places like the New England Journal of Medicine.  That is likely more studies than for any drug you've ever taken.  These studies looked at sugar differences and overall diet and found no difference.  They looked at kids getting sugar in a huge bolus, say from gorging candy bars, and found no difference.  They've even studied kids whose parents swear that they are sensitive to sugar and found no difference.  And in the best study of them all, they gave a whole bunch of kids a sugar free beverage, and then lied to a random half of the parents and told them that their kids got sugar.  Those parents rated their children as more hyperactive.  It is not the sugar.  Parents just believe it is.  This myth is entirely in their heads.  

So there are plenty of good reasons kids might act hyper when they get sugar.  Often it's at a birthday party or on a holiday or on Halloween.  Moreover, some parents are so crazy about sugar that their kids never get it, so when they do, those kids are really, really excited and hyper, but that's not because of the sugar, it's because of the parenting.  Sugar doesn't make kids hyper.  We know that because we have randomized controlled trials to prove it.  Case closed.  And next time someone tells you that they read something causes some other bad outcome, make sure you ask them if the study was a randomized controlled trial.  I can almost guarantee you it wasn't.  

Before we go, please note that there are plenty of other reasons not to give kids too much sugar, the pediatrician in me feels compelled to say that.