Dear Editor, BioMed Central, Advances in Rheumatology. We read with great interest the article "Effect of food intake and ambient air pollution exposure on ankylosing spondylitis disease activity" [1] by Narjes Soleimanifar et al. The authors touch on an important aspect of managing patients with ankylosing spondylitis (AS), especially given the increasing interest in the role of genetic, environmental and dietary factors in the pathogenesis and severity of disease. However, we would like the authors to clarify certain aspects of their work, which we strongly believe will be beneficial for the readership of Advances in Rheumatology.