A new study suggests that eating more meat, having less of certain bacteria in the gut, and more of certain immune cells in the blood all link with multiple sclerosis. The study teased out subtle connections that could lead to a better understanding of the causes of the disease.

Multiple sclerosis is an autoimmune disease affecting nearly 3 million people worldwide, costing $28 billion annually in the U.S. alone. MS is more prevalent in specific regions, particularly the northern mid-latitudes, suggesting geography is somehow linked to the disease, perhaps involving diet. But teasing out the exact relationships between diet, immune response, and MS has been difficult. 

Researchers from UConn Health and the Washington University School of Medicine studied the gut microbiome, immune systems, diet, and blood metabolites in 49 volunteers — 25 MS patients and 24 healthy controls — to look for correlations that might be subtle but important. The strongest linkage the researchers found involved eating meat. Their analysis linked higher meat consumption to a decrease in the population of Bacteroides thetaiotaomicron in people’s gut ecology. B. thetaiotaomicron is linked to digesting carbohydrates from vegetables.

Higher meat consumption, which was observed in the MS patients, was also linked to an increase in T-helper 17 cells in the immune system, and an increase in S-adenosyl-L-methionine in their blood.

The relationship between meat eating and disability and the other factors was not deterministic; some healthy people eat a lot of meat. But the pattern of all the factors suggests that, in MS, something goes wrong with people’s gut bacteria that dissociates them from the immune system, leading to heightened T-helper 17 cells and autoimmune attacks on the nervous system. And it tends to be linked to eating meat.

In the future, the researchers would like to expand the research to include more people, including those with a more severe form of MS. Eventually they hope to understand more of the cause-and-effect between diet, bacterial ecosystems in the gut, and immune response, and potentially help prevent or mitigate MS symptoms in people suffering from the disease.

The findings were published in the journal EBioMedicine.