The aim of the study was to determine how feeding rats a high‑fat diet (F) supplemented with various forms of chromium affects the responses of the immune and redox systems, as well as epigenetic changes in the ileal tissue and the course of fermentation processes in the caecum. The rats received a pharmacologically relevant dose 0.3 mg Cr/kg body weight in form of chromium(III) picolinate (Cr‑Pic), chromium (III)‑methionine (Cr‑Met), or chromium nanoparticles (Cr‑NPs). The F increased DNA oxidation and raised the level of interleukin IL‑6. The F was shown to reduce the intensity of fermentation processes in the caecum while increasing the activity of potentially harmful enzymes in the faeces. The addition of Cr in the form of Cr‑NPs and Cr‑Met in rats fed F beneficially increased mobilization of enzymes of the DNA repair pathway. All forms of Cr, but especially Cr‑NPs, beneficially decreased the activity of caecal bacterial β‑glucuronidase, faecal β‑glucosidase and β‑glucuronidase. However, due to the increase in level of cytokine IL‑2 in small intestinal wall, induced by all tested forms of chromium, it is difficult to state conclusively that this element can mitigate unfavourable proinflammatory and oxidative changes induced by a F in the small intestinal wall.