In a previous blog titled Intestinal and brain connection: profound impact on neurodegenerative diseases, we discussed the emerging significance of research on the relationship between the microbiome and neurological diseases. This field has generated growing interest, but recently concerns have arisen about potential errors that could obscure the validity of some current hypotheses. A study published in Nature Microbiology (Volume 8, August 2023, 1392–1396) analyzed common claims in this area, revealing significant misunderstandings about the microbiome. The authors emphasized the need for rigorous research standards to avoid wasting resources and losing public trust.

Despite these concerns, there is substantial clinical and preclinical evidence suggesting that the microbiome may play a key role in the susceptibility to various neurological disorders. The gut microbiota is crucial for maintaining homeostasis in bodily systems, particularly the central nervous system. Studies in experimental animals have clearly demonstrated the important role of the microbiota in various phases of three critical aspects: neuronal development, inflammation, and behavior.

Data show that the “Central Nervous System-Gut-Microbiota” axis operates bidirectionally, and its alteration can contribute to the development of diseases such as Parkinson’s and Alzheimer’s. Cross-sectional clinical studies have reinforced the concept of an altered microbiota contributing to the pathophysiology of these diseases. However, the field is nascent, and interpreting these data is difficult as the composition of the microbiome is influenced by various factors like diet and exercise.

The most robust evidence of the microbiota’s involvement in neuronal development has been obtained in germ-free mice. In these mice, the absence of microbiota and a normal immune system affects critical neural processes such as myelination and neurogenesis. However, the lack of a normal immune system in these mice weakens conclusions, as part of the response may not depend on the microbiota.

It is necessary to move from correlational to causal studies with longitudinal design, not just cross-sectional, to provide temporal context. A significant challenge in this field is identifying a healthy microbiome, as differences in microbiome composition between individuals are wide and difficult to correlate with specific diseases.

When considering the development and validity of our knowledge about the microbiota, we must take into account the complexity of the material we handle and its peculiarities. For example, the intestinal microbiome is estimated to consist of around a thousand different bacterial species, most anaerobic. This variability makes it difficult to construct solid random groups for designing clinical studies.

In recent times, most clinical studies in this field have been longitudinal, contributing to demonstrating the importance of the microbiota not only in intestinal tract diseases but also in neurological conditions. However, interpreting the data is challenging due to the existing variability, and there is a general consensus on the need for more controlled and randomized clinical studies, which offer greater interpretative solidity than longitudinal studies. Controlled studies are more robust and clear for establishing causal relationships between an intervention and its effects, providing better control over confounding variables and being more resource- and time-efficient.

Longitudinal studies and randomized controlled trials in humans are needed to determine if the microbiome can lead to new therapeutic strategies. The importance of the microbiome lies in its ability to transform an organization, facilitating not only survival but also growth and success in a competitive market. These competencies act as tools that provide stability and direction while allowing the necessary flexibility to adapt and expand.

Therefore, developing these competencies should be a strategic priority for any company aspiring to long-term success.