Interactions with the Microbiota
Our gut microbiota has been shown to have some strong impacts on our overall health when considering both the nutrition of what we consume but also the microbial interactions themselves. The effects of the microbiota extend deeper into our daily lives through our immune system, our nervous system, and our overall reactions to allergies and stress.
When considering the immune system there are two parts… the innate and adaptive. The innate are all the physical barriers (our skin) and the chemicals inside our bloodstream that stop anything that doesn’t belong in us. Adaptive on the other hand work with specificity. They run tests using signal molecules to see if a foreign contaminant is present and needs to be destroyed. T-cells send these chemical signals – cytokines – which help direct how the immune system should respond. If it detects non-host cells, it deploys the immune cells to attack any pathogens. They hold memory and can react faster if they encounter the same foreign pathogen again in the future.
There’s a whole other subsystem within the adaptive immune response – but the key concept in terms of our gut microbiota is that our immune system is constantly monitoring the load of bacteria that reside within us. Obviously, they’re foreign but our system recognizes them as non-pathogenic and allows them to reside. Immunoglobulin (IGA) affects the microbial composition of the gut, protecting beneficial microbes from immune attacks. There’s a theory that our adaptive immune response was developed to work in tandem with our gut microbiome. It’s also almost a symbiotic relationship… where our gut microbes help stimulate the actual development of our immune system.
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Now let’s consider how the gut microbiota affects those with autoimmune diseases or allergies. Autoimmune diseases are complex, incorporating a lot of factors at onset and beyond. There are studies showing links between hormone levels and autoimmunity – higher levels of estrogen tend to be linked to a higher incidence rate of autoimmune diseases.
A study on mice showed that the presence of specific microbes affected overall testosterone levels. Showing a marked increase in autoimmune diabetes in the female populations. After comparing levels between pathogen-free and gnotobiotic (controlled microbiotas) mice, performing experiments like fecal swaps, and administering drugs to lower testosterone, the overall consensus was that females showed a higher chance of developing diabetes unless interventions were in place (the fecal swap from male to female).
With allergies, genetics and environmental factors like the microbiome play a role. It’s thought that early exposure can eliminate or reduce the severity of an allergic reaction. One study that looked to link the microbiome and allergens looked at Pakistani infants who had fewer allergies and Swedish infants. It showed that the Pakistani children colonized their gut bacteria quicker because the overall lifestyle of the Pakistani people tends to be less “hygienic” than the overall Swedish lifestyle. The delayed colonization is also thought to bring a delay in the immune system, which directly affects the reaction to food particles. So while food allergies do have a genetic component, being exposed to more microbes during the early developmental cycles can stage the microbiome better to handle any potential microbiome imbalances.