Researchers at Colorado State University have identified a dietary component, tryptophan, that can be transformed in the gut into an inflammatory chemical. This byproduct, indole, may play a role in the development of arthritis. The findings were reported in the Journal of Clinical Investigation (JCI).
Tryptophan is a vital amino acid present in many protein-rich foods, including meats, fish, dairy products, and a variety of seeds and nuts. Beyond its role in protein synthesis, tryptophan contributes to the production of important enzymes and neurotransmitters. It is widely understood that humans do not synthesize this amino acid endogenously, so it must be obtained through diet.
In a controlled study using laboratory mice, researchers demonstrated that intestinal bacteria metabolize tryptophan and produce indole. As indole levels rose within the animals, autoreactive immune T cells began to emerge. Unlike normal T cells that recognize and attack foreign invaders, autoreactive T cells can mistakenly target the body’s own tissues, potentially increasing susceptibility to arthritis.
The researchers also observed that a diet rich in plant fiber might lower the likelihood of tryptophan being converted into indole. Dietary fiber supports gut function and promotes a more diverse microbial ecosystem, which appears to steer tryptophan processing toward less inflammatory pathways.
Looking at overall dietary patterns, incorporating a variety of plant-based foods in the spring meals may align with this protective effect. A balanced approach that emphasizes vegetables, fruits, whole grains, and legumes can contribute to healthier gut microbes and a more regulated immune response. These findings add to a growing body of evidence linking gut metabolism, microbial composition, and inflammatory disease risk, highlighting the potential for diet to influence immune-related arthritis outcomes (JCI).