Researchers from the University of Colorado (CU) Department of Medicine are shedding light on a complex process where common dietary components – such as tryptophan – can inadvertently fuel inflammatory diseases.
Tryptophan, an essential amino acid found in foods such as meat, fish, dairy and chocolate is widely known for its vital role in human healthaiding in protein production, muscle building and neurotransmitter synthesis.
In the present study, published in the Journal of Clinical Investigation, the researchers focused on a paradox: how tryptophan, generally beneficial to our health, can be converted by gut bacteria into compounds that escalate the risk of inflammatory diseases, including rheumatoid arthritis.
“It is now widely known that the intestinal microbiome, the bacteria in the gut, can break down tryptophan into by-products. Some of these byproducts are anti-inflammatory, but we have also associated some inflammatory causes with these products. We are the first to show which products contribute to inflammation and in what way,” explains Dr. Kristine Kuhn, co-author of the study and head of the Department of Rheumatology at the University of Colorado.
Using experiments with mice, the team demonstrated a direct link between tryptophan consumption, bacterial metabolism and the development of arthritis. By modifying the gut microbiome through antibiotics or dietary adjustments, they observed a significant impact on disease progression, identifying indole – a by-product of tryptophan breakdown – as a key inflammatory factor.
Further experiments revealed that the presence of indole was associated with an increase in certain immune cells and antibodies, signaling an increased inflammatory response. As a result, this finding opens up new possibilities for innovative therapies aimed at blocking indole production, offering a new therapeutic avenue for the management of rheumatoid arthritis and related diseases.
The study’s findings also suggest dietary strategies for mitigating arthritis risk: “A diet high in fiber and lean meat—the Mediterranean diet—seems to nudge the microbiome into a healthier state, so you get the anti-inflammatory properties of tryptophan, whereas the typical Western diet seems to drive more towards the inflammatory pathway,” explains Dr. Kristine Kuhn.
The research not only highlights the complex relationship between our diet, gut bacteria and our immune system, but offers hope for millions of people suffering from or at risk of inflammatory diseases. By unraveling the mysteries of this complex interplay, scientists are moving closer to developing targeted therapies and nutritional recommendations that could significantly reduce the burden of these debilitating diseases.