Table of Contents
Introduction
In the last couple of years, the connection between the internal gut and the brain has received increased scientific and public attention. This interaction is known as the gut-brain axis, which means that the gastrointestinal and central nervous systems are connected, as presented below.
In the light of recent studies, the gut microbiome, or the population of microorganisms residing in the human gastrointestinal tract, may play a decisive role in the state of mind. The main focus of this discourse is prebiotics, a type of dietary fiber that acts as a food source for friendly bacteria in the gut. This article aims to focus on the interaction between prebiotics and mental health to stress that these substances may be helpful in improving a person's psychological condition.
What Are Prebiotics?
Prebiotics are, therefore, food components that are not broken down by the host’s enzymes but pass through the intestinal tract and selectively encourage the growth of the desirable bacteria. While probiotics contain live bacteria that positively affect our bodies, prebiotics are a type of nondigestible food that supports the development of these helpful bacteria. Some familiar prebiotic sources are garlic, onions, leeks, asparagus, bananas, and whole grain products.
Prebiotics mainly contain non-digestible substances like complex carbohydrates, including inulin, fructooligosaccharides (FOS), and galactooligosaccharides (GOS). These compounds are not broken down in the stomach and small intestine and are transported to the large bowel, where the gut microflora acts.
Prebiotics also produce small-chain fatty acids (SCFAs) such as butyrate, propionate, and acetate. These have several health advantages, including helping digestion, boosting the immune system, and having antimicrobial activity.
What Is the Gut-Brain Axis?
The gut-brain axis is based on the communication network between the gut microbiota and the human head. This communication is done through the vagal nerve, immune system, and the formation of neurotransmitters and metabolites. The most notable of these nerves is the vagus nerve (tenth cranial nerve), which connects the gut and the brain and relays signals in both directions.
It is well established that gut bacteria can synthesize some of the critical neurotransmitters like serotonin, dopamine, and gamma-aminobutyric acid (GABA). More to the point, about 90 percent of the body’s serotonin, considered the ‘feel good’ hormone, is in the gut. This shows just how much the state of gut health can affect mental health.
How Are Prebiotics and Mental Health Related?
The study of the effect of prebiotics on mental health is not very extensive, and the research conducted thus far is rather encouraging. Some prior research has indicated that prebiotics may also benefit mental health through their impact on the gut microbiota, changes in inflammation, and the synthesis of neurotransmitters and other bioactive agents.
1. Stress and Anxiety Effect: The positive impact of prebiotics on mental health is perhaps one of the most documented effects in the literature today, and one such effect includes the relief of stress and anxiety. In the study on ten healthy adults published in Psychopharmacology in 2015, the investigators investigated the influence of a prebiotic supplement with FOS (fructooligosaccharides) and GOS (galactooligosaccharides) on cortisol levels and emotional processing.
Cortisol is commonly known as the stress hormone produced when the body is stressed and is an important element in the stress-fight response. The study discovered that the prebiotic supplement participants had reduced cortisol stress levels and provided more positive emotional reactions to stress than subjects who took a placebo.
2. Role in Depression: Depression is a complicated disease that affects the mind and is accompanied by feelings of sadness, lack of interest or pleasure, and sleep or appetite disturbance. Although it is not entirely clear what induces depression, evidence links inflammation and disruption of microbiota in the gut with depression.
These prebiotics may also help reduce some of the symptoms of depression because of their impact on the gut, the microbiota, and the inflammation markers. Specifically, an article published in 2018 investigated the effect of a prebiotic supplement on depressive-like behavior in mice. The researchers also noted that the mice that received the treatment had a lower level of depressive-like behavior and cytokines in their brains. This suggests that prebiotics could help reduce neuroinflammation, which is understood to play a role in depression.
Additionally, a cross-sectional study in Nutrients 2019 argued that prebiotics could influence mood by enhancing beneficial bacteria, including Bifidobacteria and Lactobacilli, which emit anti-inflammatory SCFAs and GABA. Therefore, these results imply the further possibility of prebiotics as a complementary treatment for depression.
3. Cognitive Function and Memory: Recent studies have concentrated on the impact of prebiotics on cognitive ability and memory. Cognitive function can be explained as several psychological processes, including memory, attention, and even problem-solving. Some research shows that prebiotics may affect cognition because of the proportional relationship between the gut and the CNS (central nervous system).
A cross-sectional study on dietary prebiotic intervention and cognitive function in rodents was published in Behavioral Brain Research in 2016. Rats fed a diet containing prebiotics were discovered to have a better memory in a maze test than normal rats. The study also noted higher concentrations of SCFAs in the brain, which are assumed to positively impact cognition by regulating neurotransmitter synthesis and inflammation.
What Are the Future Directions and Considerations of Prebiotics?
Although the existing literature indicates that prebiotics may benefit mental health, several questions remain unclear. The studies have been performed mainly in animals or small samples of people; therefore, more extensive human trials should be conducted to substantiate these observations and establish what prebiotic substances and amounts could benefit mental health status.
However, it is also important to realize that the effect of prebiotics is not entirely beneficial and that the effects depend on age, diet, and the kind of flora in the gut. It is likely that because of these factors, more traditional and perhaps personalized approaches will be required to enhance the psychological features of prebiotics.
However, prebiotics are not the only factor affecting mental health. Implementing healthy lifestyle habits such as a balanced diet, exercise, stress reduction, and sleep is crucial for an individual's well-being.
Conclusion
The existing and potential link between prebiotics and mental health is an exciting and relatively new area of investigation. With the new knowledge of the gut-brain connection, more and more people realize that adding prebiotics and other beneficial components to the diet may help improve mental health and well-being.
Of course, more research is required to understand the underlying processes behind these effects. Still, current studies point to prebiotics as a promising tool in the mental health arsenal. They can easily fit into people’s daily lives as a natural supplement to enhance psychological and cognitive well-being.
