A number of critical observations have been made over the past decade that are increasingly pointing towards small intestinal bacterial overgrowth, SIBO, as an important risk factor for developing cognitive impairment and dementia. If true, it means that you have the potential for substantially reducing risk for cognitive impairment, as well as risk for numerous other health conditions (obesity, type 2 diabetes, irritable bowel syndrome, rosacea, psoriasis, fibromyalgia, and many, many others).

There appear to be two general ways in which the microbiome can participate in adding to risk for dementia: lipopolysaccharide (LPS) endotoxemia and microbial translocation.

LPS endotoxemia refers to the release of toxic components of microbes (“endotoxin”) living in the gastrointestinal (GI) tract into the bloodstream that can then enter the brain. LPS endotoxemia has other effects that can add further to risk, such as causing or amplifying insulin resistance, another major driver of cognitive impairment and dementia. LPS endotoxemia, worst in SIBO, therefore has direct effects on brain health, as well as indirect effects via insulin resistance.

Translocation refers to the ability of microbes to exit the GI tract, mouth, or other areas and gain entry to another organ, in this case the brain. Numerous microbial species, for instance, have been recovered from brain tissue in people with dementia: the mouth microbe, Porphyromonas gingivalis; fungal species from the skin such as Malassezia; fecal Proteobacteria species, likely from the GI tract; various Candida species from the GI tract and elsewhere. It is increasingly looking like the brains of people with Alzheimer’s dementia have polymicrobial infestations, i.e., not one, but many species of microbes.

But LPS endotoxemia originating with SIBO is looking like a major culprit. For example:

  • LPS can be recovered as part of the ß-amyloid plaque that accumulates in the brains of people with dementia.
  • LPS administered to animals intravenously causes accumulation of ß-amyloid plaque
  • LPS administered to animals intravenously causes accumulation of the tau protein, another factor that accumulates in brains with dementia
  • LPS causes damage to brain cells when administered intravenously
  • LPS reduces the ability of cells in the hippocampus to respond to injury. (The hippocampus is a part of the brain that atrophies with dementia.)

As you’d predict, a recent study in which testing for SIBO testing was conducted, approximately half of people with Alzheimer’s dementia tested positive for SIBO, compared to around 20% in those without dementia. (Note the high proportion of “healthy control” participants testing positive for SIBO.) No surprise, people with dementia commonly have GI complaints such as bloating, abdominal discomfort, and diarrhea, reflecting a disrupted GI microbiome. (H2 breath testing likely underestimates the number of people with SIBO, as it does not factor in other forms of dysbiosis such as hydrogen sulfide- and methane-producing variants.)

While further research is required to better understand how microbes contribute to cognitive impairment, reversing SIBO and thereby the potential for both LPS endotoxemia and translocation is readily undertaken, is achievable, accessible, and inexpensive. No drugs or procedures are required. A terrific starting place? My recipe for SIBO Yogurt. Recall that, by restoring keystone microbial species that 1) colonize or germinate in the small intestine (where SIBO occurs), and 2) produce bacteriocins, natural antibiotics effective against the species of SIBO, we are witnessing the majority (about 90%) of people doing this normalizing breath H2 gas, indicating reversal of SIBO. I also encourage anyone engaging in making SIBO Yogurt that, even after H2 normalization or reversal of any symptoms indicating SIBO have been corrected (e.g., reversal of food intolerances, fat malabsorption, or breaking a weight loss plateau), continue the yogurt intermittently, e.g., 2-3 times per week, to prevent recurrences that are otherwise common. This seems to be working extremely well. Also recall that my recipe calls for extended fermentation of 36 hours to permit 12 or more doublings that generates around 300 billion microbial counts per 1/2-cup serving (counts obtained via flow cytometry): bigger numbers of beneficial microbes are more likely to overpower the invasion of fecal microbes that define SIBO.

SIBO, endotoxemia, and translocation of pathologic microbes are therefore factors that you have enormous influence over, thereby giving you control over your future cognitive health. As is often the case, don’t expect your doctor to have any insights into this process as, because there are no drugs or procedures to address, he/she will have virtually no knowledge of how these processes impact brain health nor what actions to take. But recognize that you have the capacity to exert major effects on your future cognitive health. Take omega-3 fatty acids, vitamin D, take other steps to eliminate insulin resistance, engage in “speed-of-processing” cognitive exercises to reduce risk for cognitive decline. But be sure to also address SIBO.