It almost seems too good to be true; eating live microorganisms, (more specifically certain bacteria also known as “probiotics”), could potentially reverse memory decline and even boost the memory capacity of healthy individuals. Although this at first may sound like complete nonsense to you, science recently started to realize that these bacteria in our gut are essential not just for digestion, but also for memory function. What’s more, researchers have found that supplementation of these bacteria by way of small changes to your diet, can actually improve brain functioning! This article explains how our gut impacts our memory and the role that probiotics play in this relationship.
Although research interest into the bidirectional relationship between our gut and brain has been sparked over the last two decades, this is not a novel concept. In fact, we are more microbe than human, since the human gut is a complex system that houses over 100 trillion microbial cells. Moreover, these microbes present in the gut can communicate with the brain via the release of neuroactive substances like gut-derived serotonin, (a neurotransmitter important for among others sleep and emotion). Besides that, the gut in itself can influence the brain via the release of among others various hormones or immune cells. Similarly, the brain can change the microbiome either in a direct manner or indirect manner, (by affecting the composition of the bacteria in the gut). With the rise of research into this field over the last 15 years, researchers have been able to better understand the interplay between our gut, the bacteria that reside in our gut, and our brain. This view has also been applied in the explanation of how the healthy and unhealthy brain are being organized and consequently how several brain functions, namely memory, can be altered. Moreover, researchers have started to believe that they have figured out a manner in which they can make use of these little creatures that colonize our gut to boost learning and memory.
How might probiotics fit in this gut-brain axis and what are they exactly? Probiotics are defined as living bacteria, which after consumption in the right amounts are known to improve or restore the gut microbiota composition. Research has established that probiotics may help in boosting your mood, cognitive function, and decreasing stress and anxiety. You might find the idea of eating living organisms disgusting, and get shivers by the idea of eating all those crazy types of foods such as: kefir, kombucha, kimchi etc. However, did you know that some of the regular foods which you are already familiar with, (yoghurt, gurkins, or sauerkraut), also contain these beneficial bacteria? So maybe without knowing you have already been eating these bacteria! However, researchers are still inconclusive about the potential of these probiotics regarding increasing learning and memory in humans, since a lot of research nowadays is done in animals.
An intriguing claim made by John F Cryan, the Principal Investigator in the APC Microbiome Institute Ireland during an episode of BBC Future in 2014 shook up the microbiotic research world; “We have unpublished data showing that probiotics can enhance learning in animal models”. However, you might wonder, does this hold true for humans as well?
A review by Kesika and colleagues in 2021, showed that several studies performed in individuals with, (a mild form of), Alzheimer’s Disease (AD), (a type of dementia in which people gradually lose their memory of various life experiences), showed an improvement in cognition after supplementation of probiotic foods. An example of such a study is one done by Hwang and colleagues in 2019, where Lactobacillus plantarum C29, a probiotic present in Kimchi, (A famous Korean side dish made from fermented vegetables), after 12 weeks of supplementation to people having a mild form of AD increased there cognitive performance. Moreover, this increase in cognitive performance was accompanied by increased blood levels of a protein called brain-derived neurotrophic factor, (BDNF), important for stimulating the growth of neurons and connections in the brain which is of course important for learning and the formation of memory.
You might wonder, how about healthy humans, can probiotics make us smarter? It seems possible at least based on a study by Kim and colleagues in 2021. In this study 63 healthy elders, (> 65 years), were supplemented either with a placebo or probiotics containing two types of gut bacteria (Bifidobacterium bifidum BGN4 and Bifidobacterium longum BORI) for 12 weeks. After 12 weeks, the probiotics group showed a greater improvement in several brain functions with among others memory. Moreover, BDNF levels were significantly increased when the probiotic group was compared to the placebo group. However, results in healthy as well as AD patients remain inconclusive, since not all studies currently being performed can replicate the results as described above.
So putting everything together, diet can definitely influence brain functioning, however, it is too early to boldly state that probiotics can increase our memory capacity and learning performance in humans. Research in this field is still ongoing regarding investigating the effects of probiotics in both the healthy and diseased population. Moreover, the way in which these probiotics enhance brain functioning has yet to be unraveled. For now, the best proven ways to boost your brain are to exercise and making sure that you sleep enough, however maybe we can supplement this advice with adding probiotics to your diet in the upcoming future.
Author: Joyce Burger