Early changes in the forestomach of rats, mice and hamsters exposed to dietary propionic and butyric acid

Groups of five male and five female rats, mice and hamsters were fed diet containing 4% propionic or butyric acid for 7 days. Evidence of damage and cellular proliferation in the epithelium of the forestomach and limiting ridge was detected in all three species. Changes were particularly marked in animals fed butyric acid diet and rats appeared to be the most sensitive species. It is postulated that tumours of the forestomach reported in rats after long-term feeding of propionic acid diet may be a consequence of continued damage and repair, and that butyric acid, which occurs naturally in foods at concentrations up to 5%, would be at least as potent as propionic acid if similarly tested.