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Eating more meat, having less of a carbohydrate-digesting bacteria in the gut and more pro-inflammatory immune cells in the blood, all link with multiple sclerosis (MS), an international team has found.
Increasingly, evidence suggests that bacteria living in our gut can affect our immune system; and what we eat can affect the bacteria in our guts. MS is particularly prevalent in the mid-latitudes including the United States and Australia, suggesting that geography and potentially local diet has some effect.
The complex study of 49 people aimed to tease out the exact relationships between diet, immune response and MS by using advanced multi-OMICS, a biological analysis approach combining multiple datasets.
The work was published in late January in eBioMedicine.
MS is an autoimmune disease in the brain, affecting fewer than three million people worldwide, but it costs $28 billion annually in the US alone. MS is an autoimmune disease in which the body attacks the insulation surrounding its nerves. When the insulation is damaged enough, the nerves begin to misfire and malfunction like wires with frayed insulation. But what triggers the body to attack the insulation in the nervous system in the first place is unknown.
Corresponding author Associate Professor Laura Piccio, initially from Washington University and now with the University of Sydney’s Faculty of Medicine and Health, collaborated with Dr Yanjiao Zhou at the University of Connecticut (UConn Health) School of Medicine to study the gut microbiome, immune systems, diet and blood metabolites in 25 MS patients and 24 healthy controls.
“This is the first study using an integrated approach to analyse the interplay between diet, gut microbiome, the immune system and metabolism and their contribution to disease pathogenesis and progression in people with MS,” said Associate Professor Piccio.
Dr Zhou from the United States said the team found a number of gut bacteria associated with MS and severity of disability of MS patients; they also found increased autoimmune markers and signature metabolites in MS.
“But what is really interesting is how these systems connect with each other, and how diet is involved in these connections,” Dr Zhou said.
The strongest systemic 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 associated with digesting carbohydrates from vegetables. This was found across all participants, including the healthy “control” group.
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 (SAM) in their blood.
In the cohort of subjects the researchers studied, the healthy control group averaged just 28 grams of meat daily compared to those with MS who averaged more than double at 70.9 grams daily. For the purposes of this study, “meat” is defined as red and white meat but not fish or seafood.
Associate Professor Piccio said the findings, while novel, were not unexpected. “It is increasingly suggested that meat should be eaten in moderation for several reasons, including that it is high in saturated fats and that it can promote the production by the gut bacteria of substances with potentially detrimental effects on our health,” she said.
The longitudinal study assessed participants at baseline and six months and involved three years of research.
A direct relationship between meat eating, the gut microbiome, peripheral immune profile and the other factors was not shown. However, the pattern of all the factors was suggestive 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 associated with meat eating.