The vitamin D status in ankylosing spondylitis in relation to intestinal inflammation, disease activity, and bone health: a cross-sectional study

Summary We assessed the vitamin D status in ankylosing spondylitis (AS) patients and healthy controls in the late winter when no vitamin D is produced by the sunlight. The vitamin D status was often poor, but not lower in AS and not associated with disease activity or signs of gut inflammation. Introduction The aims of the study were to investigate the vitamin D levels attained mainly by dietary intake in ankylosing spondylitis (AS) in comparison with healthy controls and in relation to gut inflammation, measured indirectly by fecal calprotectin, disease activity, osteoproliferation, bone mineral density (BMD), and vertebral fractures. Methods Serum 25-hydroxy vitamin D (25(OH)D) was measured in 203 AS patients and 120 healthy controls at the end of “the vitamin D winter,” when the out-door UVB irradiation is too low to allow synthesis of vitamin D 3 in the skin at the latitude of Gothenburg, Sweden. Fecal calprotectin was measured in stool samples. Disease activity was assessed with CRP, ESR, ASDAS CRP, BASDAI, BAS-G, BASFI, and BASMI. Lateral spine radiographs were scored for osteoproliferation and vertebral fractures using the mSASSS and Genant scores. BMD was measured in the lumbar spine and femoral neck. Results Vitamin D insufficiency (a serum 25(OH)D