← Questions/LIVING WITH AS
Does what I eat make a difference?
The short answer
The gut is one of the most active areas of AS research: people with AS have a different mix of gut bacteria, and HLA-B27 itself appears to shape it. The direct evidence on diet is much thinner. One study linked ultra-processed food to higher disease activity, a large UK study found no link at all between salt and AS, and the probiotic trials so far are small and mixed. Nothing here replaces treatment; eating well is reasonable and unproven.
5 papers behind this answer, best first
Clicking through to a study? How to read a paper is the ten-minute version.
Fruit and vegetable intake as a mediator in the association between ultra-processed food and disease activity in ankylosing spondylitis.
Clinical rheumatology
Among 104 people with ankylosing spondylitis in Türkiye, eating more ultra-processed food went with higher disease activity, partly because it displaced fruit and vegetables, which were independently linked to lower activity. It is a snapshot rather than a trial, so it cannot prove diet changes the disease, but it points the same way as the gut-microbiome research.
Association of dietary sodium intake with IL-17-mediated diseases in the UK biobank.
Clinical nutrition ESPEN
In the UK Biobank, higher estimated salt intake went with slightly higher odds of IL-17-driven conditions such as psoriasis, psoriatic arthritis and rheumatoid arthritis, but there was no link at all with ankylosing spondylitis. Despite plausible lab reasons to expect one, this large study does not support cutting salt as a way to influence AS.
Gut microbiota and ankylosing spondylitis: current insights and future challenges
Microbial Cell
Comprehensive review of how gut bacterial imbalance disrupts the IL-23/IL-17 inflammatory pathway and weakens the intestinal barrier in AS. Identifies the lack of standardised methodology and large cohorts as the bottleneck for translating this into treatments.
HLA-B27-associated gut microbiota and amino acid perturbations promote ankylosing spondylitis through M1 macrophage activation
Gut Microbes
Shows that HLA-B27, the gene most strongly linked to AS, reshapes which bacteria live in the gut and how the body handles certain amino acids, which in turn activates the inflammatory immune cells driving the disease. Suggests targeting the gut and these metabolic changes could become a real treatment route.
Efficacy of Probiotics in Rheumatoid Arthritis and Spondyloarthritis: A Systematic Review and Meta-Analysis of Randomized Controlled Trials
Nutrients
Meta-analysis across 13 RCTs. CRP reduced significantly (mean difference −3.04 mg/L, p<0.001) but DAS28 disease activity score showed no consistent change after excluding high-risk-of-bias trials. Biochemical signal without clinical translation; strain-dependent, L. casei and L. acidophilus show the strongest individual signals.
Plain-language guides on this from patient organisations
Reviewed sources written for patients. They cover the “what do I do” part that research papers can’t.
- NASS: Your diet and axial SpA ↗
National Axial Spondyloarthritis Society (UK)