Do you ever feel like you need a coffee and a sweet to get through your work? Well, it turns out there’s a reason for that. The combination of caffeine and glucose can improve the efficiency of brain activity, according to a recent study that used MRI to identify the effects of these two substances.

Participants were tested after drinking a study beverage containing either caffeine, glucose or the two combined or a placebo consisting only of water.

The researchers found that the combination of the two substances improves cognitive performance in terms of sustained attention and working memory by increasing the efficiency of the areas of the brain responsible for these two functions. This supports the idea that there’s a synergy between two substances, in which each one boosts the effect of the other.

The study was published in the journal Human Psychopharmacology: Clinical and Experimental.