Gut bacteria may affect MS patients’ response to diet interventions

Differences in gut bacteria may affect how people with multiple sclerosis (MS) respond to dietary interventions, according to a study.

The researchers stressed that their analysis was limited to data from a small group of people, so further studies will be needed to validate and expand on the results. Still, they said, the findings could lay the groundwork for more personalized dietary guidance for people with MS.

“In the future, it may be possible for clinicians to assess baseline gut microbiome characteristics and which diet pattern the person is most likely to benefit from,” the researchers wrote in the study, “Predicting Dietary Impact on Multiple Sclerosis-Related Symptoms With the Gut Microbiome: A Pilot Study Using Unsupervised Machine Learning,” which was published in Brain and Behavior. The work was funded by the National Institutes of Health (NIH), among others.

What a person eats can have a profound impact on their health. Currently, there isn’t a single diet considered best for people with MS. It’s generally recommended that people with MS follow dietary guidelines similar to those for the general population, emphasizing lots of fruits, vegetables, and lean proteins, and fewer highly processed and sugary foods.

Researchers are studying how different types of diets may influence outcomes for people with MS. In 2016, researchers at the University of Iowa launched a clinical trial called WAVES (NCT02914964), which tested two separate dietary interventions in MS patients: the modified Paleolithic elimination diet, also known as the Wahls diet, which excludes grains containing gluten, eggs, dairy, and soy products, while incorporating algae, nutritional yeast, and fermented foods; and the low-saturated fat diet, also known as the Swank diet, which involves cutting out saturated fats.

The main results of the WAVES study, published in 2021, showed that MS patients following either diet tended to report less fatigue and improved quality of life after a few months.

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Exploring the gut microbiome

A team including some of the same scientists wanted to explore the biological mechanisms that might explain these changes. The researchers focused on the gut microbiome, the community of bacteria and other microscopic organisms that live in the human digestive tract.

The scientists noted that a person’s diet affects the composition of the gut microbiome more than any other factor, and gut bacteria can in turn have profound effects on a person’s health and mood.

“Since diet has the biggest impact on gut microbiota composition, the beneficial effects of diet might be mediated through the modulation of gut microbiota composition and function,” they wrote.

Using fecal samples collected during the WAVES study, the researchers analyzed the gut microbiomes of 23 participants who followed either the Wahls or the Swank diet. They then used advanced computer models to look for statistical associations between specific gut microbiome features and patient-reported outcomes.

Results showed that patients who had higher levels of certain types of bacteria (such as Akkermansia, Bacteroides, Barnesiella, and Alistipes) before starting the dietary intervention were more likely to report improvements in fatigue. Conversely, patients with higher starting levels of other bacteria (Faecalibacterium, Bacteroides, and Alistipes) were less likely to report improvements in certain quality-of-life measurements.

“These exploratory findings may suggest that MS symptom improvement could be linked to bacterial presence and proportion at the start of adjunct diet therapy,” the researchers wrote.

The scientists said they are optimistic that this type of analysis could one day lead to better guidance for patients.

“Identifying baseline microbiome patterns associated with favorable clinical response to specific diet manipulation could facilitate greater personalization of the diet recommendations for patients, pending future validation,” they wrote.

The researchers also noted that gut microbiome composition tended to change over time, with distinct changes in patients who followed either diet.

“Future studies with larger and more diverse cohorts, longer dietary exposure, and [detailed characterization of gut bacteria] will be essential to validate these associations and define how diet-related microbial changes contribute to fatigue, immune function, and broader MS symptom trajectories,” they concluded.