Scientists have discovered a significant connection between gut health and arthritis, revealing how gut bacteria may contribute to the development of inflammatory diseases such as rheumatoid arthritis (RA) and spondyloarthritis (SpA).
A study led by Dr. Kristine Kuhn at the University of Colorado, published in the Journal of Clinical Investigation, shows that gut bacteria process tryptophan — an amino acid found in food — into inflammatory byproducts, such as indole, which can fuel joint inflammation. The research suggests that an imbalanced gut microbiome, known as dysbiosis, plays a significant role in the development of arthritis.
In RA, immune issues may begin in the gut years before joint symptoms appear, a period known as the “preclinical phase.” Specific bacteria, like Subdoligranulum, may contribute to this process.
Similarly, about half of SpA patients exhibit microscopic gut inflammation, supporting the “gut-joint axis” theory, which posits that gut issues can trigger joint problems.
In mouse experiments, antibiotics that cleared gut bacteria or a low-tryptophan diet prevented arthritis and reduced indole levels. Indole was found to boost inflammatory immune cells while suppressing those that maintain immune balance, worsening joint damage.
These findings point to new treatment possibilities. Dietary changes, such as adopting a fiber-rich Mediterranean diet, can promote the growth of anti-inflammatory gut bacteria.
Researchers are also exploring ways to block indole production or identify individuals at risk through blood markers to prevent arthritis before joint damage occurs.
Symptoms of Rheumatoid Arthritis (per the Mayo Clinic):
- Tender, warm, swollen joints, often starting in smaller joints like fingers and toes
- Morning stiffness and stiffness after inactivity
- Fatigue, fever, and loss of appetite
- Symptoms may spread to wrists, knees, ankles, elbows, hips, and shoulders
- About 40% of patients experience non-joint issues affecting skin, eyes, lungs, heart, kidneys, and more
- Symptoms vary, with flares of increased activity and periods of remission
This research highlights the gut’s role in arthritis and offers hope for preventive treatments targeting the microbiome.