The causes of intestinal dysbiosis: a review

Alternative Medicine Review, June, 2004 by Jason A. Hawrelak, Stephen P. Myers

Hence, antimicrobial agents should be used sparingly and selected carefully in order to minimize the impact on GIT microflora. (47)

The Effect of Stress on GIT Microflora

To determine whether psychological stress results in an altered gastrointestinal environment, Bailey and Coe investigated changes in indigenous GIT microflora in primates after maternal separation. GIT microflora was evaluated in 20 infant rhesus macaques ages 6-9 months who were separated from their mothers for the first time. All infant monkeys were found to have typical fecal bacterial concentrations at baseline. A brief increase in Lactobacilli shedding on the first day post-separation (p<0.05) was followed by a significant decrease in the concentration of Lactobacilli in the feces (p<0.001). An inverse relationship was also found between the fecal concentration of shed pathogens (Shigella spp. and Campylobacter spp.) and shed Lactobacilli (p= 0.07). The study demonstrates that psychological stress can alter the integrity of indigenous microflora for several days. (54)

Other authors have also theorized the Lactobacilli population responds to stress-induced changes in GIT physiology, such as inhibition of gastric acid release,5s alterations in GIT motility, (56) or increased duodenal bicarbonate production. (57) These changes may result in an intestinal environment less conducive to Lactobacilli survival, adherence, and replication. Alterations in GIT milieu may lead to detachment of Lactobacilli from the intestinal epithelium and subsequent passage through the GIT, thus resulting in decreased numbers of replicating Lactobacilli. This would explain the increased shedding of Lactobacilli found on the first day of stress, followed by a dramatic decrease in numbers of Lactobacilli over the next six days. (54)

The effects of psychological stress on the intestinal environment have been studied in Soviet cosmonauts. In general, it was found that on return from space flight there was a decrease in fecal Bifidobacteria and Lactobacillus organisms (Table 2). These changes were attributed primarily to stress, although a diet low in fiber may also have contributed. (58)

The change in microflora observed by Lizko led to a subsequent decline in colonization resistance, which in turn resulted in increased numbers of potentially pathogenic organisms. It has been found that exposure to psychological stress results in a significant reduction in the production of mucin and a decreased presence of acidic mucopolysaccharides on the mucosal surface. (58) Since both mucin and acidic mucopolysaccharides are important for inhibiting adherence of pathogenic organisms to the gut mucosa, a decrease in either contributes significantly to successful colonization by pathogenic organisms. (59)

Lizko states that exposure to stress results in decreased production of immunoglobulin A (IgA). As IgA plays a vital role in the defense against pathogenic organisms by inhibiting bacterial adherence and promoting their elimination from the GIT, Lizko postulates that any decrease in IgA secretion would most likely increase intestinal colonization by potentially pathogenic microorganisms (PPMs). (58)