By Pat Anson

Researchers are learning more about how some foods and drinks affect our gut bacteria -- and potentially trigger an immune system response that leads to rheumatoid arthritis (RA) and other inflammatory chronic conditions.

The latest example is a review, published in the journal Nutrients, that examines how harmful bacteria can cause a phenomenon known as “gut dysbiosis,” an imbalance of intestinal microorganisms associated with the development of inflammation and autoimmune diseases like RA.

Previous studies have shown that RA patients don’t consume enough dietary fiber, which can cause gut dysbiosis. Fiber helps restore balance by acting as fuel for hungry – and beneficial -- gut bacteria.

“Overall, the current evidence suggests that gut dysbiosis is involved in the pathogenesis of RA,” wrote lead author Andrzej Pawlik, MD, a Professor in the Department of Physiology at Pomeranian Medical University in Poland. “The diversity and richness of the gut microbiome seems to be reduced in RA.

“Diet is an essential dietary factor, but it also acts as environmental trigger. Researchers have reported a dramatic increase in the frequency of autoimmune diseases in developed countries, and some of them suggest that the Western diet could contribute to this phenomenon.”

Western diets typically have more saturated fats and are often low in dietary fiber, which is why RA patients are often told to increase their fiber consumption. One study found that RA patients who ate high-fiber bars and cereals for 28 days showed significant improvement in their physical and mental quality of life. High fiber intake also reduces the risk of obesity, diabetes, hypertension and other cardiovascular diseases.

Vegetarian and Mediterranean diets also promote the growth of healthy bacteria, slowing the progression of RA, and reducing joint pain.

“Dietary factors and interventions have a marked impact in controlling the progression of RA. Lifestyle modifications involving dietary changes such as higher fibre intake and reduced consumption of red meat should be recommended for patients diagnosed with RA,” said Pawlik, who says further studies are needed to examine the influence of probiotics and other diets on the inflammatory process.

Prevotella copri is a gut bacterium that has long been associated with rheumatoid arthritis. There are many others -- and some we’re just learning about.

A 2022 study identified a harmful gut bacteria known as Subdoligranulum didolesgii in about 20% of people diagnosed with RA. The bacterium has not been detected in the intestines of healthy people.

About 1.3 million people in the U.S. and 1 in every 100 people worldwide have RA, a a chronic autoimmune disease in which the body’s own defenses attack joint tissues, causing swelling, inflammation and bone erosion.