Effects of excess vitamin A and canthaxanthin on salivary gland tumors

Abstract

The effects of feeding semipurified diets supplemented with excess retinyl palmitate (20,000 and 100,000 IU/kg), β‐carotene (250 mg/kg), and canthaxanthin (250 mg/kg) on 7,12‐dimethylbenz[a]anthracene (DMBA)‐induced salivary gland tumors were studied in rats. None of the dietary supplements had a significant effect on tumor incidence. Tumor weights, however, tended to be lower in rats fed the dietary supplements compared with the controls. The incidence of tumor‐bearing rats with large tumors was significantly lower in rats fed canthaxanthin than in the control rats. At termination of the experiment, the levels of vitamin A were higher in plasma, liver, normal salivary glands, and the tumor of rats fed diets supplemented with the higher level of retinyl palmitate. Feeding the canthaxanthin‐supplemented diet had the opposite effect on tissue and plasma vitamin A levels. β‐Carotene supplementation was associated with higher vitamin A concentrations in the liver but not in plasma, salivary glands, or the tumor. The levels of β‐carotene were increased in tissues and plasma of rats fed the β‐carotene‐supplemented diet. The results suggest that in this experimental model, the diet‐induced modification of tissue or plasma vitamin A levels did not have an effect on tumor incidence.