Which Sugar Is the Worst for You? Study Shows What Sweets Do the Most Harm

A new study reveals that certain types of sugar could impact our cognition more than others. Jason Kempin/Getty Images for NYCWFF

Updated| Sugar rots our teeth and poses many physical health risks, but a new study suggests it could harm our brains, too. Research published in the February issue of Physiology & Behavior revealed that the so-called sugar coma might be real. Consumption of two types of sugar was associated with decreased cognitive performance.

Related: Eat Less Sugar and Keep Your Resolution This Year with These 3 Easy Tips

For the study, 49 people were given drinks sweetened by the four different types of sugar: glucose, sucrose, fructose or sucralose, the last of which was used as the placebo. Glucose is a simple sugar found in food, sucrose is best known as table sugar, fructose is a fruit sugar and sucralose is made artificially. Past studies have shown that our bodies react differently to the different forms of sweetener and researchers continue to figure out which have minimal health impacts.

After drinking the beverages, participants took three tests measuring cognitive ability: a timed task, an arithmetic-based assessment and the Stroop task, which asks people to say the color a word is printed in rather than the actual word. For example, the word "red" might be shown in blue type, so participants would have to report blue in order to be correct.

The team, from the University of Otago in New Zealand, found that people who consumed the glucose- and sucrose-sweetened drinks performed more slowly on the tests by a mean of 0.2 seconds, compared to those who drank beverages containing fructose or sucralose, reported ScienceAlert.


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"Our study suggests that the 'sugar coma'—with regards to glucose—is indeed a real phenomenon, where levels of attention seem to decline after consumption of glucose-containing sugar," study co-author Mei Peng said in a story on PsyPost. People who didn't eat for 10 hours before the study were particularly impacted by the sugar.

It's worth mentioning that this was a double-blind study, meaning neither the researchers nor participants were aware who received the placebo drinks. This approach helps prevent bias and is a standard component of rigorous scientific studies.

"While the sample size is relatively small, the effect we observe is substantial," Peng said in PsyPost. "Future research should further quantify how different brain regions change after sugar consumption—by using neuroimaging techniques. This will help us better understand how attention deficits arise after glucose consumption."

However, glucose is necessary to our bodies. Typically found in breads, cereals and fruit, our bodies need glucose as a source of fuel, reported ABC. Our bodies break down the sugar, which goes into our blood stream to nourish our bodies.

Limiting sugar intake may be best but it isn't exactly easy. A study from 2002 revealed that people who consumed copious amounts of sweet substances appeared to go through withdrawal after abstaining. As Newsweek previously reported, it may be best to start small, eliminating processed snack foods and the sweetener in your coffee.

*This story was updated with additional information about glucose.