These studies show that:

1) When people practice self-control, they have reduced glucose levels.

2) Low levels of glucose are associated with worse performance on difficult (but not easy) tasks that require self-control.

3) Consuming drinks with glucose (like lemonade) makes people have higher levels of self-control on a variety of tasks.

In one study testing point 1, glucose levels were measured, and then participants were randomly assigned to either watch a video normally, or to watch a video with words flashing in the corner of the screen that they had to ignore looking at. The act of self-control (not looking at the words) was enough to reduce glucose levels among participants.

In a study testing point 2, participant's glucose was assessed, and then they had to again show self-control by ignoring words in the corner of a screen during a movie. They then had to perform a Stroop Task. Participants who had lower glucose levels after exerting self-control performed worse on the Stroop Task (glucose and self-control were significantly correlated after the self-control movie task).

In a Study testing point 3, participants drank lemonade (or a control group drink) and then were reminded of their own death (or a control topic), which past research suggests impairs self-control. After this, they had to complete a series of word fragment completions (e.g., complete G R A _ _ with a word). If self-control is impaired by death salience, they should complete less word fragments in that condition. And, if lemonade provides self-control, drinking lemonade should protect against this. That is exactly what this study found.

In sum, self-control relies on a supply of glucose. When performing difficult tasks, you might want to drink some lemonade (or some other glucose drink) to aid your performance.

Lemonade: a vital cog to self-control.