Diet-Altering Gut Bacteria and Their Role in Multiple Sclerosis

Food may alter your gut bacteria, which may affect your MS

Do Gut Bacteria Play a Role in Your MS?
Ian Cuming/Getty Images

You may be surprised to learn that those trillions of tiny organisms called bacteria that live in your gut affect the development and functioning of your immune system.

Since the immune system attacks myelin (the protective covering around nerve fibers) in your brain and spinal cord in MS, scientists are busy exploring a potential link between MS and your gut bacteria—and more specifically, how you can alter your gut bacteria through what you eat.

Your Gut Bacteria

Up to 100 trillion bacteria live in your intestines, and they have diverse roles including digesting nutrients and fiber, protecting the lining of the gut, and helping your immune system mature and function. The type of bacteria that first composes your gut is determined by your mother during birth. But soon, the composition of your gut bacteria changes, based on a number of different factors like:

  • infections
  • stress
  • age
  • antibiotics
  • genetics

Scientists now know that your diet is a factor in how your gut bacteria changes—a factor that is a lot more within your control (unlike your age or your DNA). Scientists believe that what you eat affects your gut bacteria in two ways:

  •  the type of bacteria that grow in your intestines (called your bacterial composition)
  • the bacteria's metabolic activity (the products they make and how this influences the rest of the body, especially your immune health)

    How Diet Affects Your Gut Bacteria

    A small but fascinating 2014 study in Nature shows just how rapidly diet can affect your gut bacteria. In this study, ten participants were instructed to eat a plant-based diet for five consecutive days, consisting of mostly fruits, vegetables, legumes, and grains. Examples of foods in this diet included:

    • granola
    • fresh mangos and papaya
    • jasmine rice
    • banana chips
    • fresh carrots and butternut squash
    • frozen spinach and peas

    Likewise, ten other participants were instructed to eat an animal-based diet for five consecutive days. This diet consisted of cheeses, eggs, meats, and cream.

    The participants provided daily stool samples, starting from four days prior to the diet and ending six days after the diet. On the days prior to and after the diet, the participants were asked to eat normally. The stool samples were analyzed for the type of bacteria present and their bacterial products.

    Results showed that the gut bacteria of the participants changed after consuming their designated diets, particularly in those consuming the animal-based diet. For instance, there was an increase in the number of bile-resistant bacteria present. This makes senses as the animal-based diet is high in fat, and with higher fat content, the body releases bile salts to aid in digestion, so bacteria that can tolerate the acidity of bile will thrive.

    In addition to the change in the composition of the bacteria, bacterial gene expression was also altered. For example, in the guts of the participants on the animal-based diet, there were more products of amino acid fermentation (protein breakdown) and less carbohydrate fermentation, as seen in the plant-based diet.

    This change in bacterial products is important, as plant-based diets are higher in fiber, and the bacterial fermentation of fiber produces something called short-chain fatty acids, or SCFAs. These SCFAS create an anti-inflammatory effect in the body—so they calm down your immune system, which could potentially prevent a myelin attack (theoretical at this time).

    The big picture here is that diet can quickly change your gut bacteria, which may influence your immune health (and therefore your MS).

    Are Gut Bacteria the Middlemen in MS?

    It's important to remember that MS is a complex disease that probably arises from a combination of both your DNA and one or more environmental triggers. This means that a genetic predisposition along with a trigger likely leads to the development of MS. While scientists have isolated a number of potential MS-related genes (and are still working on that), the precise environmental trigger (or triggers) is still debated.

    That being said, it's possible that these bacterial organisms that live by the trillions in your intestines are the middlemen—the mediators between a person's trigger and their immune system becoming out of balance.

    For instance, maybe potential MS-related triggers (like a virus, low vitamin D levels, obesity, smoking, or a high salt diet) alter the bacteria in your gut, which then triggers your immune system to start attacking your central nervous system.

    If this is the case, people with MS may share the fact that their gut bacteria is changed (and not in a good way—towards a more pro-inflammatory state), but have unique triggers for how that change came about.

    What Does This Mean for MS Treatment?

    The fact that your gut bacteria may play a role in whether you develop MS or in your current disease state suggests that therapies like probiotics and maybe even fecal transplantation (where stools are transferred into your intestines) could be used in the future. That being said, scientists need to first tease out the precise role of bacteria in MS, like which type of bug or bugs promote or reduce MS activity, if any.

    In addition, a diet that promotes healthy gut bacteria (one that promotes an anti-inflammatory state) may be helpful, although we cannot say for sure. Regardless, a diet rich in fiber and low in fat (lots of fresh fruits, vegetables, and whole grains) will improve your overall physical health.

    As research continues on the role of your gut bacteria and how factors like diet affect it, we will develop a clearer picture of how to best incorporate nutrition into our everyday lives.


    Bhargava P., Mowry E. Gut microbiome and multiple sclerosis. Curr Neurol Neurosci Rep. 2014. Oct;14(10):492.

    David LA. et al. Diet rapidly and reproducibly alters the human gut microbiome. Nature. 2014;23:505(7484):559-63.

    Joscelyn J. Kasper LH. Digesting the emerging role for the gut microbiome in central nervous system demyelination. Mult Scler. 2014;20(2):1553-9.

    Continue Reading