OBJECTIVES: Preclinical and clinical data suggest, that the microporous mineral with large inner surface and ion exchanger capability PMA-(Panaceo-micro-activation)-zeolite can bind irritating and inflammation associated chime-constituents. We hypothesised whether or not it can ameliorate subclinical inflammation, and investigated the potential in the management of patients with Irritable Bowel syndrome (IBS). METHODS: The trial design was prospective, randomized, controlled, double-blinded, pilot study with 41 patients. They received orally 3 g of the medicinal product PMA-zeolite or microcrystalline cellulose (control) twice a day. At baseline and after three months the symptom load, blood and stool parameters, like high sensitivity C-reactive protein (hsCRP), zonulin, α1-antitrypsin, interleukin IL-10, and changes in the gut microbiome were determined by means of ANOVA, ANCOVA and non parametric statistical analyses. RESULTS: The IBS-associated symptom scores decreased significantly in both groups (p=0,001) indicating a strong placebo effect. In the verum but not in the placebo group various inflammation related laboratory parameters decreased. The gross statistical comparison revealed a reduction of α1-antitrypsin significant (p=0,037), a lowered inflammation marker hsCRP, paralleled specific microbiome changes (Lactobacillus, Bifidobacteria, and Firmicutes). CONCLUSIONS: The decrease of blood hsCRP and decreased stool α1-antitrypsin suggest that PMA-zeolite possibly can lower inflammation in the gut of IBS patients. The corresponding increase of the immune modulating species Bifidobacteria and Lactobacillus and the reduction of Firmicutes also point at an inflammation ameliorating effect and a possible mucous layer strengthening effect. The protocol of this explorative pilot study is feasible for a sufficiently powered trial on inflammation amelioration in IBS patients.