How sugar destroys your concentration

Do you ever experience an afternoon slump? Like trouble concentrating, low energy, no ideas? Many people reach for something sweet to combat this. However, sugar may not be the remedy but the cause of the brain fog.

A 2018 study in the journal Physiology & Behavior investigated the effects of different kinds of sugar on thinking skills in 49 healthy young adults. The participants had to fast or drink sodas with either regular sugar, fruit sugar, or a sweetener with no calories without being aware which drink they were given. Subsequently, they had to complete tasks that had them press buttons as quickly as possible, do mental maths, or follow complex rules. Participants who drank sodas with regular sugar performed worse on all of these tasks. Participants who had nothing or drank sodas with fruit sugar did equally well.

This may sound counterintuitive. After all, our brain runs on sugar. So, eating sugar should give our brain more fuel. However, our body tightly regulates sugar levels in our blood. When we eat something containing regular sugars, the blood sugar level rises. All of this circulating blood sugar is potentially harmful. So, insulin is released to store the excess sugar for future use. The insulin signal overshoots, leading to a lower blood sugar level than the baseline. This overshoot is thought to cause the slump after sugar consumption.