As Bryant Jonkees wrote earlier on this blog, processes like switching quickly between different tasks and actively holding and manipulating information in memory all expend a shared ‘mental resource’ in the brain. In other words, your brain is an engine that runs on limited fuel. Tyrosine is a way to refill that fuel. And most interestingly, tyrosine can be taken as a food supplement – but is also naturally contained in foods such as almonds, cheese and bananas.

Switching between different tasks is a process that is often thought to be modulated by dopamine, of which tyrosine is the chemical precursor. We therefore asked 22 participants to come to our lab on two mornings, separated by one week. Participants were instructed to fast overnight, and upon arrival we asked them to drink some orange juice. What they did not know, is that on one occasion, 2 grams of a neutral placebo were dissolved in this orange juice, and on the other occasion 2 grams of tyrosine – for half of the participants, this order was switched. One hour after they finished drinking the juice, we asked them to perform what is called a switch-task.

This task requires you to switch from focusing on letters to focusing on numbers, and vice versa. Basically, there are four blocks on the screen of the participant. Whenever a letter-digit pair appears in the upper half of the screen, you have to press one of two buttons in order to indicate if the letter is a vowel or a consonant. However, when the pair appears in the lower half of the screen, you have to press a button to tell if the number is odd or even.

What we found is that, when participants are given enough time to prepare to switch between the two tasks, tyrosine improved the performance on this task and made participants significantly faster at switching. This indicates that tyrosine helps people to overcome the conflict that arises whenever you are switching between two tasks.

These findings show, once again, that the food we eat influences the way we perceive the world and act upon it. Most excitingly, perhaps in the long term, we may be able to use this in our advantage.

Steenbergen, L., Sellaro, R., Hommel , B. & Colzato , L. S. (2015). Tyrosine promotes cognitive flexibility: Evidence from task-switching performance. Neuropsychologia.