The brain uses chemicals called neurotransmitters to help it send signals. But these are carefully balanced: too much or too little of one neurotransmitter can cause problems and has been associated with a number of neurological and mental health conditions. Although some drugs can alter neurotransmitter levels, these often have negative side-effects. This project explores whether changes to the diet or taking vitamin supplements might be a suitable alternative.
If successful, the work could one day lead to nutritional recommendations for individuals with particular conditions including epilepsy, anxiety and depression. These might work in combination with more traditional treatments in order to reduce symptoms.
For this project our interdisciplinary team drew on expertise in psychology, neuroscience, chemistry and biology. Our study aimed to alter levels of a neurotransmitter called gamma-aminobutyric acid (GABA) which has an inhibitory effect on brain activity; it stops the brain from over-reacting. To do this, we gave human participants a substance rich in chemicals that the body uses to make GABA (its 'precursors', or ingredients). This substance is widely available in supermarkets under the brand name Marmite and contains high concentrations of GABA precursors including vitamin B6, vitamin B12 and glutamate.
Participants who ate one teaspoon of Marmite each day for a month showed reduced brain responses to flickering visual stimuli, compared to measurements taken at the start of the study. This could be because GABA levels had been increased by the intervention and inhibition was greater. Control participants, who ate peanut butter instead, showed no such reduction in activity.
Our findings were reported in the Journal of Psychopharmacology and received extensive media coverage from around the world. It was the University's top news story for that year.
The initial result demonstrates that diet can affect how your brain works, but there are still many questions left to answer.
A follow-up study with collaborators at the University of Reading found that vitamin B12 alone can also alter brain responses to whisker stimulation in rats.
Colleagues at York are currently working to replicate and extend this work in humans using B12 supplementation, including making measurements of GABA in the brain with an MRI scanner. In the future, when the basic mechanisms are better understood, we aim to begin testing patient groups who might benefit from increased GABA levels.