expert opinion

The Link Between Gut Health and Stress

Michael Roizen, M.D.

March 2, 2018

Since 1979, Americans have experienced an increase in stress, according to research (8). In that time frame, the average score on the Perceived Stress Scale (PSS-10®, a stress assessment instrument) was 12.1 for men and 13.7 for women (higher numbers indicate more self-perceived stress). These scores are considered low to moderate stress.

Often I’ve wondered how stress causes inflammatory changes in the body. The BIG DADDY hormone of stress—cortisol—suppresses inflammatory processes. So how does stress cause inflammation? Before now I attributed that effect of stress to the fact that it increases blood sugar, and increased blood sugar feeds inflammation.

New Research
But a new study (1) from Brigham Young University and published in Nature may have given us an explanation. In this study, one group of female mice ate a high-fat diet, and another group were exposed to stress. Not surprisingly, the mice that ate the high-fat diet showed changes in their microbiome — the balance of bacteria in their digestive tract — that are linked to inflammation and chronic illness. To simplify the study (1) results, stress causes some specific bacterial species inside the body to thrive. The consequence of this stress-induced bacteria thriving in the body is inflammation.

Intestinal Microbiome
Stress changes the bacteria inside the body to be similar to those if you ate a diet that fosters inflammation. Right now, 10 trillion members of 500 species of bugs – some good, some bad – call your intestines home.  The trick is to make sure the good outnumber the bad.

The same foods that foster your health – namely vegetables, fruit, legumes, walnuts, olive oil, and the rest of the delicious Mediterranean-style menu – are the same foods that help change the bacteria inside of your intestine (called your intestinal microbiome) to be healthier. In addition, there are more probiotic-containing foods such as fat-free no-sugar added yogurt, kimchi, sauerkraut, miso (miso soup), kefir, sourdough bread and naturally fermented sour pickles, tempeh and of course, dark chocolate.

Eating the right foods and adding a probiotic supplement can support your intestinal microbiome, all the way down to the good bugs.

Life Stages and The Gut
As people age, they may lose bacterial diversity in the gut. That’s why I take a daily probiotic and I try to populate my gut with different healthy strains of bacteria. Daily probiotic supplements have been show in other scientific studies to have different health benefits, including decreasing occasional diarrhea after using an antibiotic (2-7). The latest pre-clinical study uncovers an emerging new use of probiotics – blocking stress-induced inflammation (1).


  2. Reid, G.; Jass, J.; Sebulsky, M.T.; McCormick, J.K. Potential uses of probiotics in clinical practice. Clin. Microbiol Rev. October 2003 vol. 16 no. 4 658-6721 October 2003.
  3. Szajewska, H.; Kotowska, M., Mrukowicz JZ.; et al. Efficacy of Lactobacillus GG in prevention of nosocomial diarrhea in infants. J Pediatr. 2001. 138, 361–365.
  4. Bartlett, J. G. Clinical practice. Antibiotic-associated diarrhea. N. Engl. J. Med. 2002. 346:334-339
  8. Roizen MF, Roach KW . Wellbeing in the workplace. BMJ 2010;340:c1743