Chronic fatigue and the microbiome

12/01/2016

There is tremendous interest in the relationship between the microbes in and on our bodies and our state of health and disease. The origins of chronic fatigue syndrome have remained mysterious, though studied, for years, but it is now believed to be related in some ways to the bacteria in our gut.  

Chronic fatigue syndrome, or C.F.S., is a condition in which normal exertion leads to debilitating fatigue that isn’t alleviated by rest. It has no known triggers, and its diagnosis requires lengthy tests administered by an expert. Now, for the first time, Cornell University researchers report that they have identified biological markers of the disease in gut bacteria and inflammatory microbial agents in the blood.

In a study published in the June edition of the journal Microbiome, the team describes how they correctly diagnosed chronic fatigue syndrome in 83 percent of patients through stool samples and blood work, offering a step toward understanding the cause of the disease.

“Our work demonstrates that the gut bacterial microbiome in chronic fatigue syndrome patients isn’t normal, perhaps leading to gastrointestinal and inflammatory symptoms in victims of the disease,” said Maureen Hanson, a professor in the Department of Molecular Biology and Genetics at Cornell and the paper’s senior author. “Furthermore, our detection of a biological abnormality provides further evidence against the concept that the disease is psychological in origin.” 

The Cornell researchers collaborated with Dr. Susan Levine, a specialist on chronic fatigue based in New York City, who recruited 48 people diagnosed with the syndrome and 39 healthy controls to provide stool and blood samples. The team sequenced regions of microbial DNA from stool samples to identify different types of bacteria. 

Overall, the diversity of types of bacteria was greatly reduced and there were fewer bacterial species known to be anti-inflammatory in C.F.S. patients compared with healthy people, an observation also seen in people with Crohn’s disease and ulcerative colitis. At the same time, the researchers discovered specific markers of inflammation in the blood, likely due to a leaky gut from intestinal problems that allow bacteria to enter the blood.  Bacteria in the blood will trigger an immune response, which could worsen symptoms.

The researchers have no evidence to distinguish whether the altered gut microbiome is a cause or a consequence of disease. In the future, the team will look for evidence of viruses and fungi in the gut, to see whether one of these or an association of these, along with bacteria, may be causing or contributing to the
illness.

The researchers concluded that when they have more information, clinicians could consider changing diets, using prebiotics, such as dietary fibers, or probiotics to help treat the disease.

Probiotics are microorganisms believed to provide health benefits when consumed; the term is currently used to name ingested microorganisms associated with benefits for humans and animals. The introduction of the concept is generally attributed to Nobel recipient Élie Metchnikoff, who postulated that yogurt-consuming Bulgarian peasants lived longer lives because of this custom. He suggested in 1907 that “the dependence of the intestinal microbes on the food makes it possible to adopt measures to modify the flora in our bodies and to replace the harmful microbes by useful microbes.” 

Although some claims for probiotics have not been substantiated, randomized controlled trials at the Tuebinden University Hospital in Germany published in 2016 found that certain commercially available strains of probiotic bacteria, when taken by mouth in adequate doses for one to two months, possess treatment efficacy in certain psychological disorders, such as anxiety, depression, autism spectrum disorder and obsessive-compulsive disorder. They also improved certain aspects of memory.   

Prebiotics are non-digestible fiber compounds that pass undigested through the upper part of the gastrointestinal tract and stimulate the growth or activity of advantageous bacteria that colonize the large bowel by acting as substrate for them. Most fruits and vegetables have indigestible fiber; some of the most effective are onions, garlic, leeks, wheat bran, asparagus, chicory and raw banana.

There will be a symposium on the microbiome, in healthy soil and in the human body, on Sunday, Dec. 4 at 2 p.m., at Commonweal in Bolinas. The microbiome is a subject of substantial current research and excitement, with a relationship to many aspects of health and disease. 

 

Sadja Greenwood, a Bolinas resident, is a retired physician formerly active at the University of California, San Francisco.