AbstractIn a study of the effects of carotenoids, canthaxanthin (CA),β‐apo‐8'‐carotenal (BA), orβ‐carotene in an extract ofSpirulina‐Dunaliellaalgae (AE) was fed at 0%, 0.1%, or 0.2% in a choline‐deficient (CD) diet. In each of eight groups, 10 adult male Fischer 344 rats were fed diets with designated carotenoid sources and levels or a choline‐sufficient diet for 12 weeks. Carotenoids altered some of the changes induced by the CD diet. Increases in enlargement of fatty livers and low plasma cholesterol levels occurred in rats fed 0.2% BA. Plasma retinal was further reduced 35% by BA or AE. BA and AE increased liver total vitamin A about 80% and 305%, respectively. Liver lipid per oxidation was enhanced and plasmaα‐tocopherol was reduced further by 1.0% AE. AE, BA, and CA (mg/g fat) depressed liverα‐tocopherol about 49%, 67%, and 78%, respectively. The decreased liverα‐tocopherol was concurrent with an increase in carotenoid stores of CA>BA>AE. Histopathological examination of sections of liver tissue by light microscopy showed fatty and cirrhotic changes in all rats fed CD diets. Histochemical evaluation based on a semiquantitative assay revealed a marked increase in peroxisome enzyme activity in the livers of all CD rats. None of the carotenoids appeared to have any effect on the development of morphological changes in the liver. Although carotenoids can function as antioxidants, they did not prevent changes observed in rats fed CD diets.