Anecdote: I have reactive arthritis comorbid with ulcerative colitis. I was getting debilitating arthritis flares once a month until I stopped eating gluten, peanuts, and added sugar. I haven't had an arthritis flare since eliminating these foods.

My rheumatologist wanted to put me on methotrexate but I declined out of fear if the side effects. He never mentioned anything about diet, but clearly a dietary intervention worked for me.