Dietary approaches that target the gut microbiome can improve brain disorders

Microbiome refers to the collective genomes of microorganisms that live in a particular environment. Bacteria refer to the community of microbes themselves. For example, the human digestive system contains approximately 100 trillion microorganisms (mainly bacteria, but also viruses, fungi and protozoa). These microorganisms play essential roles in human immune and energy metabolism, extending from digestive health to brain behavior and function. However, whether “feeding the microbiome” can help modulate human behavior and brain function is under debate.

The positive impact of diets is mediated or controlled by the gut-microbe axis. Recent studies have highlighted germ signatures in psychiatric disorders. This has led to the development of microbiome-targeting therapies known as “psychology”. This included the management of the organisms, nutritional interventions to reshape the function and composition of the microbiome, and faecal microbiota transplantation. Among these treatments, the most common test is the administration of probiotics (Lactobacillus And the Bifidobacterium strains, either alone or in combination) in subjects with clinical depression.

Research on the effect of dietary treatments, both whole food interventions and specific dietary factors, on the gut microbiome, is very limited. However, the effect of diet can be ubiquitous and lead to neurodegeneration and neurodevelopment. Thus, modulating the gut-brain axis could be an important approach to treating and preventing mental health disorders. However, most of these interventions are at an early stage of research, and importance must also be given to the limitations of such interventions.

Posted a new review in Therapeutic Nutrition and Metabolic Care The journal focused on studies that used targeted nutritional gastrointestinal microbial interventions to improve mental health conditions. He also discussed some suggestions for developing more robust and beneficial interventions for studies of the diet and the microbiome.

Stady: Diet and the gut microbiota-brain axis: a raw material for clinical nutrition. Image Credit: Pikovit / Shutterstock

The gut-brain microbiota axis

The gut-brain connection primarily involves neuro-immune-endocrine pathways that are vulnerable to dietary changes. Short-chain fatty acids (SCFAs) are most commonly produced as a result of microbial processing of indigestible dietary fibres. SCFAs can control energy balance, feeding behavior, and immune functions.

Synthesis of several key neuroactive molecules, such as catecholamines, beta-aminobutyric acid (GABA), tryptophan metabolites, and serotonin (5-HT), occurs in the gut microbiota. It has been observed that these molecules interact with the autonomic nervous system or stimulate sensory neurons in the intestine. This leads to activation of neurons in path nucleus loner (NTS), the location from which information travels to different brain regions.

A healthy diet containing live bacteria or phytochemicals can enhance the production of SCFA and other bioactive compounds that can positively affect metabolic health, digestive health, and brain processes. However, a Western diet that includes processed foods, high sugar, salt, and saturated fats can alter the composition of the microbiota and lead to low-grade systemic inflammation, which can be associated with metabolic disorders, gastrointestinal disease, obesity and mental illness.

Impact of dietary interventions targeted to the gut microbiome on mental health

Recent studies have indicated that the gut microbiome plays a role in mental health. For example, fewer genera of SCFA-producing and more genera of lactic acid-producing bacteria have been associated with many different psychiatric disorders. Moreover, recent clinical trials have highlighted that dietary interventions can improve depression and symptoms of other mental disorders.

The Mediterranean diet is one such diet that was previously reported to promote health. They were first tested along with conventional antidepressant treatment in the SMILES trial and were reported to significantly improve symptoms for patients with major depressive disorder. Other studies have also reported that the Mediterranean diet was able to improve depressive symptoms in both children and adults. However, most of these studies focused on behavioral outcomes rather than on the effect of diet on the gut microbiome.

Fermented foods such as kombucha, kefir, and yogurt have been reported to improve metabolism and digestive health. However, studies on its effect on the brain and behavior outcomes are limited. Other diet-related approaches to targeting the gut microbiota axis and microbiota include intermittent fasting and ketogenic diets.

How to design a microbiome diet behavior study

Assessing the effects of diet, microbiome, and behavior in humans can face various kinds of complexities. One of the most important challenges is the lack of standardized protocols or interventions for nutritional assessment.

Approach to assessing dietary intake

Assessment of nutritional intake can occur through direct methods such as refined diets, direct observation, and nutritional biomarkers or indirect (self-report) methods such as food frequency questionnaires (FFQs), 24-h diet withdrawals, and food diaries. However, all subjective methods rely on the participant’s self-report, perceptions, and experience and may be subject to issues of misreporting and systemic bias.

Objective methods such as nutritional biomarkers are free from reporting problems and bias. Some nutritional biomarkers include total vitamins and minerals in urine, plasma, serum, energy intake, phytochemicals, metabolites of caffeine, isoflavones, carotenoids, and phytosterols. However, the use of nutritional biomarkers in conjunction with self-reported data provides optimal results.

The use of FFQs to assess dietary intake can have several advantages, such as low cost, low participant burden, and rapid and automated analysis of data. However, self-report, this is based on memory and also limited to the food items on the list. False reporting was observed in the case of FFQs is higher than in other methods, such as food diaries. Food diaries also have certain specifications, such as time-consuming data entry, greater participant load, and human resources with experience in dietetics. These limitations can be reduced with the help of technology.

Designing nutritional interventions that target the microbiome

Attention should be paid to the different aspects of designing a nutritional intervention that targets the microbiome. Factors such as the duration of the intervention, the extent of the change in diet, and the competition of microorganisms are suggested to play important roles. An assessment of the participants’ basic diet and characteristics of feeding behavior is also required to understand the impact of the intervention. Finally, the participant must be willing to commit to changes in diet, which can include unusual cooking methods, new foods, and shopping habits.


Studies of diet and the microbiome and their impact on brain health are an emerging area of ​​research. Although several studies have shown the effectiveness of diet in regulating microbiome composition which in turn improves celiac, metabolic disorders and mental illness, these studies have limitations that require further work. The development of new nutritional interventions involves determining the optimal length of the intervention and compliance with diet characteristics. More research is needed to design new nutritional interventions and improve current nutritional guidelines for acute disease prevention.