Does Sugar Keep You Awake? What the Research Actually Shows

Does sugar keep you awake? Not the way caffeine does. Sugar isn't a stimulant, and one carb-heavy study meal even helped people fall asleep faster. But a diet high in sugar has been linked to lighter, more broken sleep, and many sweet things, like cola, sweet tea, energy drinks and chocolate, carry caffeine that really can keep you up.

So the honest answer is: a dessert probably won't stop you falling asleep, but what's in it, and how you eat day to day, may affect how well you sleep.

Does eating sugar before bed keep you awake?

There's no good evidence that a sweet snack before bed makes it harder to fall asleep. If anything, one study found the opposite. In a small lab study of 12 healthy young men, a high-glycemic-index rice meal (one that raises blood sugar quickly) eaten 4 hours before bed cut the time to fall asleep from about 17.5 minutes to 9 minutes, compared with a low-glycemic-index meal. The same meal eaten 1 hour before bed helped less.

That doesn't make sugar a sleep aid. The study used a rice dinner, not candy or soda, it was tiny, and it measured only one night. It does suggest that "sugar keeps you awake" is too simple.

The bigger issue with late sugary snacks is usually timing and size. A large dessert right before bed can bring on heartburn, which is why it helps to finish eating a couple of hours before you lie down. See how long before bed you should eat.

Does sugar affect sleep quality?

Possibly. A diet higher in sugar has been linked to more nighttime awakenings, though the evidence is limited. In a controlled study of 26 adults who normally slept 7 to 9 hours, people who chose higher-sugar foods during the day had more arousals, brief wake-ups during sleep, that night. Eating more fiber was linked to more deep sleep, and more saturated fat to less.

Two caveats matter here:

• It was a link, not proof. People who ate more sugar may have differed in other ways.
• It was one day of free eating. It tells us about a single night, not about months of habits.

Put those two studies together and the picture is mixed: a carb-heavy meal may help you nod off, while a sugar-heavy diet may make sleep a bit lighter. Neither is strong enough to build rules around, beyond the usual advice to eat plenty of fiber and not too much added sugar.

Is the "sugar high" in kids real?

Research says no. In controlled studies, sugar didn't change children's behavior or thinking. A meta-analysis in JAMA pooled 23 double-blind studies in which children got either sugar or an artificial sweetener, and neither the kids, parents nor researchers knew which. Across 14 different measures of behavior and cognition, sugar made no reliable difference.

The authors suggested parents' strong belief in a sugar high may come from expectation and from the settings where kids eat sugar, like parties and holidays, which are exciting anyway. They couldn't rule out a small effect or effects in some individual children.

So if a child is wired at bedtime after a birthday party, the party is the likelier reason. A late night, a sugary drink that also contains caffeine, or an off-schedule bedtime will matter more than the frosting.

Hidden caffeine in sweet drinks and chocolate

This is where "sugar" really can keep you awake: many sweet drinks and treats contain caffeine. Cola, sweet black tea, energy drinks and chocolate all do, and the amounts add up.

Caffeine has an average half-life of about 5 hours. This table shows how much is still in your system at an 11:15 PM bedtime (the sleep calculator's standard bedtime for a 7 AM alarm), and the latest time each drink drops below 25 mg by bedtime.

Energy drinks vary a lot, from about 40 to 250 mg per 8 oz, so check the can. For specific sodas, see how much caffeine is in Coke.

Chocolate is the sneaky one at dessert time. Milk chocolate has little caffeine, but dark chocolate has noticeably more, and a whole bar adds up. Caffeine in dark chocolate has the numbers by cacao percentage.

What to eat or drink in the evening instead

Go caffeine-free after mid-afternoon and keep evening sweets small and early. A few simple swaps:

1. Choose caffeine-free soda or herbal tea at dinner instead of cola or sweet black tea.
2. Pick fruit, yogurt or a small bowl of cereal over a big dessert if you want something sweet before bed.
3. Save dark chocolate for earlier in the day, or keep it to a square or two after dinner.
4. Finish dessert 2 to 3 hours before bed if you're prone to heartburn.

If you're cutting sugar and caffeine and still lying awake most nights for weeks, talk to a doctor. Ongoing insomnia is common and treatable, and diet is rarely the whole story.