What's the Connection Between Gut Health and MS?

Only a decade ago, most scientists thought the gut was responsible for digestion. That was the beginning and end of the story. Turns out, there's much more to the tale.

"We now know there are trillions of microorganisms in the large and small intestines, and 90 percent of our immune system is in the gut," says Dr. David A. Hafler, professor of neurology and immunobiology at Yale School of Medicine. "Because multiple sclerosis is an autoimmune disease, a chronic condition in which the body abnormally attacks parts of its own nervous system, scientists are looking into the role of bacteria in our guts ( microbiome) and how it might influence MS."

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"In MS, the immune system attacks the protective sheath (myelin) that covers nerve fibers and causes communication problems between the central nervous system (brain and spinal cord) and the rest of the body. Eventually, the disease can cause the nerves themselves to deteriorate or become permanently damaged," the Mayo Clinic website states. The National Multiple Sclerosis Society says signs and symptoms of MS vary widely and depend on the amount of nerve damage and which nerves are affected. Common symptoms of MS include fatigue, vision problems, difficulty walking, muscle weakness, stiffness and spasms, and bladder and bowel problems.

Not all 400,000 people in the U.S. diagnosed with MS have the same symptoms, but researchers are finding they share one thing in common: different kinds of bacteria in their guts than people who don't have MS. Specifically, a 2014 study in the journal Neurology conducted by scientists at Brigham and Women's Hospital in Boston showed that patients with MS have more archaea (a microbe that triggers inflammation) and less butyricimonas (a microbe with anti-inflammatory properties) than people who don't have MS.

Although researchers can't confirm the microbiome is linked to autoimmune diseases, mounting evidence is pointing in that direction. These findings can have broad implications. "Since gut bacteria influences inflammation and the immune system, MS isn't the only autoimmune disease that's affected by the amount or the type of bacteria in the gut," explains Dr. Augusto Miravalle, associate professor of neurology at the University of Florida College of Medicine. "Other autoimmune illnesses, such as rheumatoid arthritis, Type 1 diabetes, Crohn's disease, colitis and asthma are also affected by bacterial balance."

But Hafler points out that this isn't the whole picture, either. "There are a number of other factors at work when it comes to the gut connection. We know that MS is caused by a combination of environmental and genetic influences. In order for gut bacteria to be a trigger, a person would also need a genetic predisposition to developing an autoimmune disease such as MS."

The genetic component may be why the link between the gut and autoimmune attacks in MS begin early in life. A 2016 University of British Columbia study, reported in the journal BioMed Central, examined gut bacteria and immune markers in 15 children with MS and nine children without the disease. The researchers found certain types of gut bacteria and specific immune markers in the children with MS and not with the healthy children.

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Scientists have also discovered geography is in play when it comes to gut bacteria and multiple sclerosis. "For example, MS sufferers living in California have a different microbiome than patients living in New York," Miravalle says. "But that might be associated with the amount of sunlight and vitamin D. We still don't know." Still, the geographic-gut bacteria-MS connection appears so promising, the National MS society has funded the MS Microbiome Consortium, which brings microbiome and geographical data together in order to explore the relationship.

Another gut factor influencing the development and frequency of relapse in MS appears to be salt intake. "There have been a few reports showing that salt can hasten MS-like disease by influencing the microbiome and autoimmune reaction,"Miravalle says, pointing to a study of 16 people published in the August 2014 Journal of Neurology, Neurosurgery & Psychiatry. The study showed that people with MS who had higher sodium intake were at approximately three times higher risk for an increase in symptoms as well as disease activity, compared with those with lower sodium intake.

Even though diets high in salt have been associated with high relapse rate in adults, this link has not been found in pediatric MS. However, high fat intake has been associated with increased relapse in children with multiple sclerosis, according to research presented at the 32nd Congress of the European Committee for Treatment and Research in MS.

A microbiome theory that affects both pediatric and adult MS is intestinal permeability, more commonly known as "leaky gut syndrome." The connection has been gaining steam in the MS research community for the past several years. "Leaky gut is a condition that allows harmful substances like toxins, microbes and waste to pass out of the intestines and into the body cavity," Hafler explains. In a 2014 study published in PLOS ONE, researchers at Lund University in Sweden found a link between increased permeability of the intestines and MS, but only in a lab setting. The scientists looked at intestinal tissue from mice infected with an MS-like disease and found not only was leaky gut involved, but there was also increased inflammation in the intestinal mucous membranes of the mice even before they showed symptoms of MS. "Inflammation plays a role in MS, as inflammatory T-cells attack the protective myelin coating of nerve cells in the brain and spinal cord," Miravalle explains.

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For now, most of the research into gut bacteria and MS is still in a comparatively early stage, and for the most part, human studies are focusing on describing the microbiome of MS patients. "While these studies show a link,"Hafler says, "we still don't know if the bacteria are different because of MS or if the changes in types of bacteria can cause MS or contribute to relapses."

Stay tuned for updates.

Robin Westen is a freelance Health reporter at U.S. News. She's an award-winning journalist who has written for numerous national magazines, including AARP, Family Circle, Psychology Today, MORE, Health, Self, Parents, Glamour and Cosmopolitan, in addition to others. She has authored more than a dozen books on health and relationships, including "The Yoga-Body Cleanse," "The Complete A to Z for Your V," "Ten Days to Detox" and "808 Conversation Starters for Couples," among others. Westen also won an Emmy for her writing on the ABC show "FYI."