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We have a gut feeling—of the importance of intestinal microbes in MS


The gastrointestinal (or GI) tract host a world of bacteria (small intestine photo credit decade3d-anatomy). online/Shutterstock).

There is still so much about the world of bacteria and other microbes inside our gastrointestinal tract, or gut, that we need to discover.  We are just beginning to explore this internal domain, and, in the past several years, scientists have made some interesting observations.   The entirety of bacteria and other microbes living within each of us—also called our microbiome—is unique to each of us.  This microbiome can be influenced by where we live (developed country v.s. developing country), what we eat (more animal products v.s. more vegetables) and what medications we take (for example, antibiotics used to treat bacterial infections in our body may also kill some of the “friendly” bacteria in our gut).

You have probably heard that statistic that up to to 70% of your immune system resides in your gut.  What does this really mean?  The longest portion of our gut is [ironically] called the small intestine.  In an adult male it averages 20 feet in length, but if it were completely spread out it would cover roughly 2,700 square feet (about the size of a tennis court).  This area is home to a large portion of immune cells.  Communication between our immune cells and the usual bacteria in our gut, means that our immune system recognizes these bacteria as “friendly.”  When rogue bacteria invade our gut we can get a stomachache, or worse, but the “friendly” bacterial residents co-exist peacefully with us, and even contribute to our well-being.

Do changes in the types of bacteria in our intestinal tracts influence our health or do changes in our health affect our intestinal bacteria?  It may be a little of both. Scientist have noticed differences in the types of bacteria present in the intestinal tracts of people with inflammatory bowel disease.  Other autoimmune diseases, such as type I diabetes mellitus and rheumatoaid arthritis, may also be impacted by the intestinal microbial milieu.  The communication between our gut bacteria and our immune system goes beyond helping our immune system to recognize the bacteria as “friendly”—these interactions may influence immune cells throughout our body.  How might gut microbes affect MS, and how in turn might MS affect our gut microbiome?



Gut bacteria may play a role in the immune system (bacteria photo credit Knorre/Shutterstock).

In mice, gut bacteria may play a key role in the development of an MS-like disease (EAE).  When animals from a spontaneous mouse-model of MS are raised in a sterile, germ-free environment, they show either no symptoms, or very mild symptoms of the disease.  However, when gut bacteria from mice reared in less sterile conditions are re-introduced into the gut of these germ-free mice, they develop the MS-like disease. This is not a simple cause and effect but a complex relationship.  The bacteria from mice raised in relatively normal conditions do not cause MS, but they do seem to be required for the development of MS.  Furthermore, introduction of a mixture of “good” bacteria into the intestinal tract of another mouse model of MS, may have a beneficial effect.  Mice treated with this specific probiotic mixture show suppression of immune signals usually associated with MS.

In humans the role of gut “flora” in the development of MS is currently a topic of great interest.  A preliminary report from a recent  American Academy of Neurology meeting describes differences in the  bacterial species residing in the gut of people with or without MS.  Certain gut species (called Archaea) were found at higher levels in MS patients compared to people without MS.  Moreover, two anti-inflammoratory bacterial species (Butyricimonas and Lachnospiraceae) were found at lower levels in MS patients, but their levels were increased by MS treatment.  At this same meeting, a Boston-based research group presented preliminary evidence  of an association between levels of vitamin D in the blood of people with MS and levels of a gut bacteria, ruminococcaceae, thought to have anti-inflammatory effects.  This may be another reason to consider a vitamin D supplement.

Just as you may talk to your doctor about taking a vitamin D supplement to ameliorate your MS symptoms, you may want to ask your physician whether you should supplement the good bacteria in your gut. You can accomplish this by taking a probiotic supplement or by making a few additions to your diet.   Probiotic foods include not only yogurt and keifer but sauerkraut, Korean kimchee, Japanese miso or nato and Idonesian tempeh.  How exactly the intestinal microbiome may affect MS remains to be seen, but research into this area will undoubtedly increase our understanding of how the human microbiome interacts with the immune system, which may have a significant impact on our understanding of immune disorders, like MS.



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