The gastrointestinal microbiome is rife with many different bacteria. Most are relatively benign, however, some major species, such as E. coli and B. fragilis are known to secrete pro-inflammatory neurotoxins. Normally these are contained within the GI tract, but they can become very deadly if exposed to the central nervous system. It has been proposed that the health of the microbiome may have an impact on Alzheimer’s disease.

A recent prospective study has reported bacterial lipopolysaccharides (LPS) in certain parts of Alzheimer’s disease brains. They determined that advanced cases of Alzheimer’s disease resulted in increased amounts of LPS, up to a 26-fold increase. Bacterial LPS may be able to bypass the normal barriers of the body, which contain other bacterial species. This allows LPS to escape from the microbiome and access the central nervous system. As the body ages and membranes and other inflammation wear down barriers, dangerous toxins can escape from the microbiome. In order to prevent the dangerous nervous issues that can arise from this, gastrointestinal health should be maintained as well as possible.

Zhao, Y., Jaber, V., & Lukiw, W. J. (2017). Secretory Products of the Human GI Tract Microbiome and Their Potential Impact on Alzheimer’s Disease (AD): Detection of Lipopolysaccharide (LPS) in AD Hippocampus. Frontiers in Cellular and Infection Microbiology, 7, 318.