Protein Found In Meat Linked To Increased Risk Of Arthritis

A new study reveals how the common protein tryptophan – primarily found in meat and dairy – can increase the chance of developing arthritis.

The study, published in the Journal of Clinical Investigation (JCI), indicates that when the gut’s bacteria breaks down tryptophan, it produces a compound that induces an inflammatory response – thereby triggering rheumatoid arthritis (which primarily affects the joints) or spondyloarthritis (which affects the spine and joints).

Rheumatoid arthritis impacts up to one percent of the population, mostly women. It causes painful swelling of the hands, feet, and joints, or even deformities if left untreated.

“The microbiome – the bacteria in our gut – can break down tryptophan into byproducts,” explained Kristine Kuhn, study co-author and head of the University of Colorado’s Division of Rheumatology, in a release by UC’s Department of Medicine.

“Some of those byproducts are anti-inflammatory, but we’ve also associated some inflammatory causes of those products,” continued Kuhn. “We’re the first to highlight which products are contributing to inflammation, and how they are doing that.”

A diet rich in ‘plant-based fibers’ might help

Photo shows a spread of animal-derived foods, including raw meat, cheese, milk, and eggs — Adobe Stock Tryptophan mostly comes from animal products like meat, dairy, and eggs

Tryptophan is an amino acid that naturally occurs in a variety of protein-dense, mostly animal-based products such as beef, lamb, pork, poultry, and dairy, along with certain plant-based foods like nuts, seeds, and legumes.

The body does not produce tryptophan but does require it in order to make melatonin (which supports healthy sleep) and serotonin (which affects pain, well-being, and sexual desire). The new study indicates that tryptophan is broken down into anti-inflammatory products by our bodies’ cells, but into inflammatory ones by bacterial cells.

Kuhn notes that the question of how to tip the balance so tryptophan goes towards the anti-inflammatory pathway rather than the one that increases arthritis risk is where research should go in the future. In the meantime, following a plant-based diet might help.

“A diet that’s rich in plant-based fibers and lean meats – this whole Mediterranean diet – seems to push the microbiome into a healthier state, so that you are getting the anti-inflammatory properties of tryptophan,” explained Kuhn. “The typical Western diet seems to go more toward the inflammatory pathway.”

While Kuhn’s study is breaking new ground, it’s not the first to link meat consumption with arthritis. Conversely, studies also indicate that eating more plant-based foods can alleviate the symptoms of rheumatoid arthritis, though the topic requires more research. Multiple studies have found that plant-based diets lower disease risk generally.