Sweet Lies

The sugar-behavior myth, the science that debunked it, and why we still believe it

Rachel was dreading the temple retreat. She wasn’t worried about the long car ride, the communal meals, or the spotty cell service. She was worried about dessert.

“There’s going to be so much sugar,” she told me anxiously. “Cereal for breakfast, juice boxes everywhere, cookies after dinner. And when Eli eats too much sugar, he becomes a different kid.”

She explained that sugar made her nine-year-old son totally hyperactive. Sometimes, if he ate too much sugar, he even got agitated, snapping at other kids or complaining loudly. Even worse than the initial hyperactivity was the crash that followed, complete with intense moodiness, tears over minor frustrations, and exhaustion that somehow made him less likely to go to bed. How could she possibly get Eli to avoid sugar when every other child would be eating their bodyweight in it?

I didn’t doubt her observations. Rachel knew her son. But when I told her that these problems probably weren’t caused by sugar, she was surprised.

She’s not alone. At this point, it’s pretty much conventional wisdom that sugar causes behavior changes in kids. But science doesn’t support it.

To be clear, when it comes to sugar and behavior, we’re not lacking evidence. This isn’t some emerging area where scientists are still piecing together preliminary findings. On the contrary, we have decades of high-quality research, including meta-analyses that synthesize results across many studies, suggesting that sugar doesn’t cause behavior problems in children. So if the evidence is this compelling, why do so many of us remain convinced otherwise?

I think the issue dates back to 1975 when pediatric allergist Benjamin Feingold published the book Why Your Child Is Hyperactive. He proposed that certain things added to our food, including sugar, were responsible for hyperactivity and other developmental problems in children. Here was a doctor offering a villain and a solution, and his book resonated with parents struggling with their kids’ difficult behaviors.

Even after subsequent research failed to validate his claims, people remained attached to this idea. And now, decades later, the message is constantly amplified on social media where clickbaity misinformation spreads faster than peer-reviewed research ever can.

But the thing that really cements the sugar-behavior connection is that our own eyes seem to routinely confirm it. Think about where children typically consume a lot of sugar. Birthday parties. Holiday gatherings. School celebrations. Temple retreats! These environments are all stimulating and exciting. Kids are running around with their friends, staying up late, and energized by noise and activity. Of course they’re hyperactive! And many get agitated and crash afterward.

But we must remember that correlation is not causation! When we test sugar consumption in calm, controlled environments, the behavior effects disappear. It’s the party, not the cake, that’s causing them to act chaotic.

When we reconceptualize the problem as behavioral and environmental, there’s actually a lot we can do to help.

For instance, I thought Eli would do better if he knew what to expect, so I suggested that Rachel spend some time reviewing the schedule and the activities with him in advance. I also figured that Eli would probably need some quiet time in the midst of a very busy schedule, so I suggested that Rachel build in breaks throughout the day. Finally, Rachel and I discussed Eli’s early signs of agitation. Rachel told me that, typically, he’d be silly and loud before he had a full meltdown. So we agreed, if she saw things moving in that direction, they should leave the activity early and avoid a problem altogether, rather than trying to power through and dealing with it afterward. None of these strategies were as simple as dietary modifications, but they directly addressed what was going on.

Rachel left our conversation reassured about the retreat, but I continued to wonder how we solve the larger problem of misinformation. Individual correction helps, but it doesn’t scale. The forces perpetuating common parenting myths are powerful and self-reinforcing.

Unfortunately, scientists bear some responsibility. Research papers sit behind paywalls, written in technical language inaccessible to most. Scientists rarely engage directly with parents, and when they do, they sometimes come across as dismissive or condescending toward people’s lived experiences. So when parents hear conflicting messages—a viral TikTok versus a study—they often trust the source that seems to understand their actual life, even if that source is technically wrong.

We need scientists who are also skilled communicators, who can meet parents with empathy and evidence. They must not dismiss parents’ observations—Rachel really does see Eli struggle when he’s amped up on junk food—but instead reframe what those observations mean.

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Loved seeing this surprise guest at halftime yesterday!