The randomized controlled trial provides tentative evidence that probiotic supplementation might improve working memory.
While prebiotic supplements have shown promise in improving aspects of cognition and mood, much of the research has relied on isolated supplements rather than whole-diet approaches.
To participate, individuals had to meet specific health criteria, including avoiding probiotic supplements and fermented foods before the trial.
The participants were randomly assigned to one of four groups: Probiotic group: Received probiotic supplements while maintaining their usual diet.
Participants in the probiotic group demonstrated a small improvement compared to the placebo group.
A recent study in Nutritional Neuroscience looked at the effects of probiotic supplements, a diet high in prebiotics, or both (synbiotic treatment) on cognitive function in adults with low mood and potential for dietary improvement. There is preliminary evidence from the randomized controlled trial that taking probiotic supplements may enhance working memory. The researchers stress the need for larger studies to confirm these effects, but the findings are preliminary.
Interest in the gut-brain axis and its possible connection to cognitive function has grown in recent years. Via neural, hormonal, and immunological pathways, the gut-brain axis is a sophisticated, two-way communication system that connects the brain and digestive system.
This relationship revolves around the gut microbiota, which are trillions of microorganisms that live in the digestive tract and have a significant impact on behavior and brain function. These microorganisms generate a range of metabolites, including neurotransmitters and short-chain fatty acids, which have an effect on mood, memory, and attention as well as inflammation regulation.
Probiotics are live microorganisms that, when taken in sufficient quantities, have health benefits and can be used to affect the gut microbiota. Probiotics, often obtained through supplements or fermented foods like kefir and yogurt, can improve the synthesis of healthy metabolites, lower inflammation, and help restore the balance of the gut microbiota.
Probiotics may enhance cognitive function, especially in clinical populations or under stress, according to some research, by focusing on mood and brain health pathways. The data is still contradictory, though, as other research indicates that taking probiotics has little to no effect on cognitive function.
Prebiotics, which are indigestible dietary fibers that provide nourishment for good gut bacteria, have also been studied for their effects on the gut-brain axis in addition to probiotics. Prebiotics, which are found naturally in foods like whole grains, fruits, vegetables, nuts, and legumes, promote the development and activity of beneficial gut bacteria, which results in the synthesis of substances like short-chain fatty acids that aid in brain function.
Much of the research has focused on individual supplements rather than whole-diet approaches, despite the fact that prebiotic supplements have demonstrated promise in enhancing mood and cognitive functions. This distinction is significant because prebiotic-rich diets may provide longer-lasting and more extensive benefits for gut health.
Probiotic supplementation, a prebiotic-rich diet, and their combination were compared in an 8-week randomized controlled trial to determine whether gut-focused interventions could produce quantifiable improvements in mental health in adults with low mood and room for dietary improvement.
The SMILES trial, the first RCT to show the strong potential of diet to alleviate depressive symptoms, served as our inspiration. Tanya Freijy, a PhD candidate at the Florey Institute of Neuroscience and Mental Health at The University of Melbourne, Australia, said, “At about the same time, we noticed a growing body of literature on the impact of probiotic and prebiotic supplements on mental health, providing evidence for the involvement of the gut-brain axis.”.
However, there was a lack of comprehensive dietary strategies to enhance gut health and, consequently, mental health. We modified Monash University’s High Fibre, High Prebiotic Diet for our study after speaking with Professor Jane Muir, one of the principal investigators behind the program. “.”.
In the study, 118 adults between the ages of 18 and 65 who had low daily intakes of prebiotic fiber and reported moderate psychological distress were included. In order to be eligible, participants had to fulfill certain health requirements, such as abstaining from fermented foods and probiotic supplements prior to the trial. Conditions related to the gastrointestinal tract, mental illnesses, pregnancy, or use of specific medications were among the exclusion criteria.
One of four groups was randomly selected from among the participants.
Probiotic group: While continuing to eat their regular diet, they were given probiotic supplements.
Prebiotic diet group: Received placebo capsules and ate a diet high in prebiotics.
Probiotic supplements and a high-prebiotic diet were given to the synbiotic group.
Placebo group: Continued eating their usual diet while taking placebo capsules.
The Cogstate Brief Battery, a computerized test that gauges working memory, processing speed, attention, and visual learning, was used to administer cognitive tests to participants at the beginning and conclusion of the trial. Reaction time and accuracy were used to assess performance.
Supplementing with probiotics seemed to have the most promising, albeit slight, impact. The findings implied that working memory, one of the primary cognitive processes involved in storing and modifying information for brief periods of time, might be improved. Comparing the probiotic group’s participants to the placebo group, there was a slight improvement.
“But until the evidence is repeated in larger studies, ideally with more sophisticated measures of cognition, it remains inconclusive,” Freijy told PsyPost.
Conversely, there was minimal evidence that the prebiotic-rich diet affected processing speed, a metric that gauges how rapidly and precisely participants can complete easy tasks. The prebiotic group’s performance was marginally worse than that of the placebo group. The researchers warn that since no previous studies have documented cognitive impairments from prebiotics, this finding might have been a statistical anomaly rather than a real adverse effect.
“The positive effects the same dietary intervention had on mood, anxiety, sleep, and perceived stress in our previous publication were unexpected and inconsistent with the prebiotic-induced impairment in processing speed,” Freijy said. This finding is most likely the result of chance, according to a closer look at the data. “.”.
No obvious evidence of a synergistic or additive effect was found in the synbiotic group, which included probiotic supplementation in addition to a diet high in prebiotics. Put differently, the cognitive results from combining the two interventions were not better than those from either treatment alone. According to the findings, any effects of the probiotic and prebiotic interventions were independent and did not substantially interact.
“Another surprising discovery was that the synbiotic treatment (high-prebiotic diet plus probiotic supplement) did not improve cognitive function, which was not what we expected,” Freijy said.
The findings may have been impacted by a number of limitations, the researchers noted. For example, the study was not specifically designed to measure cognitive effects, and the sample size was relatively small. Furthermore, the subjects were non-clinical, generally healthy adults, so cognitive function might have been near its natural maximum. This might restrict the ability to identify advancements.
The researchers are still hopeful about the wider ramifications of their work in spite of these obstacles. “Our goal is to connect the changes we saw in mental health and cognition with our microbiome analysis from this project, which is currently being prepared,” Freijy told PsyPost. We anticipate publishing the results of our microbiome research in the future. In order to support future research and possibly clinical practice, we also hope to publish more information about the viability of our high prebiotic diet protocol. “.”.
This research is part of the Gut Feelings trial, a broader gut-brain initiative. Our main publication about the impact of our clinical trial on mental health is openly accessible online. For information on nutritional psychiatry and the most recent studies on nutrition-based strategies for the prevention and treatment of mental illnesses, we suggest The Food and Mood Centre at Deakin University. “”.
