The sugar crash might be real—but not the sugar rush

Ditch the sachets.
Ditch the sachets.
Image: Reuters/Cathal McNaughton
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We all know the feeling you get after chugging a 20-ounce Coke and chomping down on a pack of M&Ms—that rush of sugar to the body that kickstarts a sudden burst of energy. And we all also know about the ensuing sugar crash that comes hours after the earlier fix starts to wane.

But according to a study published online last week in the journal Neuroscience & Biobehavioral Reviews, only one of those might be real.

Researchers from universities in Germany and the UK undertook a meta-analysis of 31 previous studies on the subject, which included a total of 1,259 participants. They looked at the effect of consuming carbohydrates on mood, and found no evidence to support the existence of a sugar high. A decrease in alertness and an uptick in fatigue, however, was associated with consuming sugar even soon after ingesting it.

“We hope that our findings will go a long way to dispel the myth of the ‘sugar rush’ and inform public health policies to decrease sugar consumption,” wrote Elizabeth Maylor, a psychology researcher and one of the paper’s authors, in a release published by the University of Warwick.

The meta-analysis was limited to healthy adults, so certain groups of individuals might indeed exhibit different sensitivities to sugar. It also looked at sugar consumption in isolation, so the effect of your average energy drink, which is loaded with both sugar and caffeine, was not determined.

The research is noteworthy given just how much sugar is consumed across the globe, in both rich and poor countries. The most recent agricultural outlook (pdf) published by the Organization for Economic Co-operation and Development and the UN’s Food and Agricultural Organization reported a per capita demand for sugar of about 32 kilograms a year, between 2015-2017, in the US. Latin America and the Caribbean, a poorer region of the world, consumes even more.

The World Health Organization recommends people keep their “free sugars” intake (sugars that are added and some naturally occurring, like in honey and syrup) below 10% of the total daily calories they consume. That might be easier said than done, though, as free sugars are found in many everyday packaged foods—from low-fat yogurts to ketchup and pasta sauces.

In the past decades, a big culprit when it comes to free sugars are soft drinks. Consumption of them in the US ballooned 135% from the 1970s to the 2000s, according to figures cited by the study.

Fewer Americans, however, are downing sugary drinks these days (paywall) than in the decade prior, in part due to growing awareness about its health consequences. Plus, if there are no mood benefits of consuming added sugars, that might give more people pause before reaching for the fizzy sweet stuff.