Our study aimed to systematically review the evidence about the effect of diet or dietary supplements on spondyloarthritis (SpA) disease activity.

a systematic literature review (SLR) was conducted in MEDLINE, EMBASE, Cochrane and SCOPUS according to the “PEO” format (Population, Exposure, Outcome). The population was SpA (axial or peripheral, axSpA/pSpA, including Psoriatic Arthritis-PsA); the intervention any kind of diet/dietary supplement; the outcome disease activity. Inclusion criteria were: adult patients, Randomized Controlled Trials (RCTs) and longitudinal studies (so that a pre-and post-intervention assessment were available), papers in English. Risk of bias (RoB) was conducted with different tools according to the design of the study.

Literature search yielded 1390 publications, of which 15 were finally inlcuded: 12 interventional and 3 observational studies. Among those with the lower RoB: a) 2 RCTs, one at unclear and one at low RoB, failed to show benefit of probiotics in SpA b) Two RCTs at unclear RoB provided evidence that weight loss, but not hypocaloric diet, was associated to MDA achievement in PsA. The remaining interventional studies were at high RoB. Among the observational studies, one study on Mediterranean diet demonstrated an association between diet adherence and a ≥ 20% decrease of ASDAS in axSpA. The other two observational studies were judged of poor quality.

weight loss seem to be able to impact disease activity in PsA, while probiotics do not seem useful in SpA; evidence for dietary behaviors is scarce and heterogeneous.