Marmite is a British brand of food paste made from yeast extract - a food additive created from brewer's yeast.
While Marmite is one of the most popular sandwich spreads in the United Kingdom, not everyone is a fan. Its powerful, distinctive flavor is so divisive that even its manufacturers, Unilever, launched a "Love It or Hate It" campaign in the mid-1990s, a slogan that has followed the brand ever since.
A new study, however, could turn Marmite hatred on its head, after finding that the yeast extract may increase levels of a neurotransmitter associated with healthy brain function.
Researchers from the University of York in the U.K. found that adults who ate a teaspoon of Marmite every day experienced a reduced response to visual stimuli, which is an indicator of increased levels of gamma-aminobutyric acid (GABA) in the brain.
GABA is a neurotransmitter responsible for inhibiting the excitability of brain cells, helping to restore the optimal balance of neuronal activity required for healthy brain functioning. Put simply, GABA "calms" the brain.
Previous studies have associated low GABA levels with an increased risk of numerous neurological and mental health disorders, including anxiety, depression, autism, and epilepsy. As a result, researchers have been investigating ways to boost GABA levels in the brain.
The new study - recently published in the Journal of Psychopharmacology - suggests that dietary modulation may be one way to reach this feat.
Marmite may increase GABA levels
Senior author Dr. Daniel Baker, of the Department of Psychology at York, and colleagues enrolled 28 adults to their study and randomly allocated them to one of two groups.
One group was required to eat one teaspoon of Marmite every day for 1 month, while the other group - the control group - was required to eat one teaspoon of smooth peanut butter daily.
The researchers note that Marmite is high in vitamin B-12, which previous studies have associated with increased GABA levels.
At the end of the 1 month, all subjects underwent electroencephalography. This was used to measure their brain activity in response to visual stimuli in the form of flickering lights.
The researchers explain that responses in the visual cortex are heavily influenced by GABA, and they point to a previous study that found responses to visual stimuli increased by 300 percent after a GABA inhibitor was administered in rats.
"This 'response gain' effect should provide a clear index of GABA availability in cortex, in that increasing GABA concentration should reduce the neural response evoked by visual stimuli to below normal levels," explain the authors.
Compared with the brains of participants who consumed peanut butter, the brains of subjects who ate Marmite demonstrated a 30 percent reduction in responses to visual stimuli, indicating an increase in GABA levels.
The reduction in visual stimuli responses associated with Marmite intake persisted for around 8 weeks after the study ended, the team notes.
"The high concentration of vitamin B-12 in Marmite is likely to be the primary factor behind results showing a significant reduction in participants' responsiveness to visual stimuli," says Dr. Baker.
'Promising example' of how diet can alter brain processes
While the researchers are unable to make any firm conclusions about whether Marmite can boost brain function, they believe that their findings indicate that dietary changes may have a long-term impact on brain function.
"This is a really promising first example of how dietary interventions can alter cortical processes, and a great starting point for exploring whether a more refined version of this technique could have some medical or therapeutic applications in the future.
Of course, further research is needed to confirm and investigate this, but the study is an excellent basis for this."
First author Anika Smith, Ph.D., Department of Psychology, University of York
"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," adds Dr. Baker.
However, the researchers stress that at present, they are unable to make any therapeutic recommendations based on their findings.