The study suggests that dietary choices could have a major impact on brain chemistry and functioning through a specific neurotransmitter known as GABA.
Writing in the Journal of Psychopharmacology, the randomised trial of 28 people found that those who consumed a teaspoon of Marmite every day for one month showed around a 30% reduction in their brain’s response to visual stimuli, compared to a control group who ate the same amount of peanut butter.
Increases in GABA are believed to reduce brain cell excitability, while too little GABA has been suggested as a major factor in certain neurological disorders including epilepsy.
Led by first author Anika Smith, from the University of York, the team behind the study commented that since Marmite consumption appears to increase GABA levels, the study is the first to show a dietary intervention can affect these neural processes.
"These results suggest that dietary choices can affect the cortical processes of excitation and inhibition - consistent with increased levels of GABA - that are vital in maintaining a healthy brain,” said Smith.
"As the effects of Marmite consumption took around eight weeks to wear off after participants stopped the study, this suggests that dietary changes could potentially have long-term effects on brain function.”
Paving the way
Dr Daniel Baker, senior author of the paper, added that the high concentration of vitamin B12 in Marmite is most likely to be factor behind results.
"Since we've found a connection between diet and specific brain processes involving GABA, this research paves the way for further studies looking into how diet could be used as a potential route to understanding this neurotransmitter,” he added.
According to the UK’s NHS Choices ‘Behind the Headlines’ service, the early stage study interesting, but are a long way from showing that yeast extract spreads like Marmite can help with conditions like epilepsy or other neurological disorders.
“At this point, we don't know what effect – if any – the changes in brain response have on the people involved,” concluded NHS Choices.
“It's also important to be aware that the suggested effects on epilepsy have not been tested on people with epilepsy. No-one with epilepsy should be tempted to stop taking their medicines in favour of Marmite.”
Baker added that the study is “a really promising first example” of how diet could alter cortical processes, and “a great starting point” to explore if refined version of the study technique might have therapeutic applications.
“Of course, further research is needed to confirm and investigate this, but the study is an excellent basis for this,” he said.
The study was carried out by researchers from the University of York and was funded by the Wellcome Trust and the Leverhulme Trust.
The Leverhulme Trust was set up by the founder of Lever Brothers, now Unilever, which manufactures Marmite. However, the trust says it does not seek to influence the topic or study design of research when it provides grants.
Source: Journal of Psychopharmacology
Published online ahead of print, doi: 10.1177/0269881117699613
“Dietary modulation of cortical excitation and inhibition”
Authors: Anika K Smith, et al