As modern people, we swim in a sea of factors that disrupt our microbiomes, the composition of microbes that dwell in and on our bodies—skin, mouth, airways, gastrointestinal (GI) tracts, and just about every other organ in the human body. Such factors include prescription antibiotics, antibiotic and herbicide and pesticide residues in food, anti-inflammatory drugs, stomach acid-blocking drugs, and many others.

But what about the role of stress? Not transient minor day-to-day stresses like being late for work or irritation with your spouse, but chronic profound stress like a bad marriage, taking care of a parent with declining cognitive function, or severe financial problems. We’ve known for years that such severe stress disrupts the composition of the intestinal microbiome—but how? How can an emotional state generate changes in the species composition of creatures inhabiting your GI tract?

Well, the science has progressed and tells us that, yes, indeed: chronic stress introduces dramatic changes into the composition of the microbiome and the integrity of the intestinal barrier. It does so because:

  • Stress hormones epinephrine and norepinephrine are triggers for the proliferation of Enterobacteriaceae, the species of small intestinal bacterial overgrowth, SIBO. Some species of SIBO, such as E. coli, Serratia, and Proteus, also produce their own stress hormones that further feed their proliferation.
  • Stress increases intestinal permeability—This means that increased levels of microbial breakdown products such as lipopolysaccharide (LPS) more readily enter the bloodstream. Increased LPS causes greater release of stress hormones and increased release of mediators of inflammation such as IL-6, IL-1 beta, and TNF-alpha.

All this adds up to cause the so-called hypothalamic-pituitary-adrenal (HPA) axis to become overactive, increasing release of cortisol. Increased cortisol causes weight gain, increases insulin resistance and blood sugar, and further adds to unhealthy changes in the intestinal microbiome. (Germ-free mice, i.e., mice bred without any microbiome, have a HPA axis that is in overdrive, suggesting that a healthy microbiome keeps the HPA axis downregulated.) An overactive HPA axis also further increases intestinal permeability, essentially causing a vicious cycle that makes matters worse over time.

How to correct this mess, a situation shared by many, perhaps most, modern Americans that fuels weight gain/obesity, insulin resistance and type 2 diabetes, hypertension, increased risk for heart disease, depression unresponsive to antidepressants, other mental illness? If you have any of these conditions or have high cortisol levels identified, for instance, via a 4-sample salivary cortisol test, the solution, you can appreciate, is to not “treat” the high cortisol with something like phosphatidylserine or ashwagandha, but to address the dysbiosis, increased intestinal permeability, and endotoxemia that are driving the high cortisol. Not only is this smarter, but it helps avert all the long-term consequences of dysbiosis and SIBO.

It would be nice if we could just say “Get rid of the stress,” but life does not generally work that way. So you can take concrete actions against the changes in your microbiome caused by stress. Start with basic efforts outlined in all of my books (Wheat Belly Revised & Expanded edition, Undoctored, and now Super Gut that contains the most comprehensive strategies) that includes frequent consumption of fermented foods and prebiotic fibers. For further advantage, you can also specifically restore microbial species that play an outsized role in rebuilding a healthy microbiome and intestinal barrier, including:

  • Lactobacillus helveticus R0052 and Bifidobacterium longum R0175
  • Bifidobacterium longum 1714
  • Bifidobacterium infantis—several strains, including EVC001
  • Lactobacillus reuteri—I believe that multiple strains work here. (Just avoid the NCIMB 30242 strain, as it lacks a bacteriocin.)
  • Lactobacillus gasseri—BNR17 and SBT2055
  • Pediococcus pentosaceous—uncertain strains but obtained via kimchi, fermented sauerkraut, and some fermented meats. (See my Defiant Health podcast’s sponsor, Paleovalley, for fermented grass-fed meat stick that have been fermented with Pediococcus and Leuconostoc, two champions of bowel health. Enter discount code “DEFIANT for a 15% discount.)

And others. We do so not by taking probiotics, but by fermenting one or more of these microbes by making yogurt using my method of prolonged fermentation to increase bacterial counts to the hundreds of billions per serving, numbers that yield greater benefits. See other posts in this DrDavisInfiniteHealth Blog on how to do this or get my Super Gut book that has many such recipes to choose from.