The effect of different levels of dietary beta-carotene on DMBA-induced salivary gland tumors.

Different levels of beta-carotene (0, 5, 25, 125, and 250 mg/kg diet) were tested for their chemoprevention effects using 9,10-dimethyl-1,2-benzanthracene-induced salivary gland tumor model in rats. Tumor incidence and tumor weights were slightly lower in rats fed diets supplemented with 25 mg or more beta-carotene/kg diet. Hepatic vitamin A and beta-carotene levels were increased in a dose-dependent fashion, reaching a plateau at 125 mg beta-carotene/kg diet. In plasma, beta-carotene concentrations were also increased with an increase in dietary beta-carotene. Vitamin A levels in plasma were not affected. The normal salivary glands had higher concentrations of beta-carotene than did the tumors. The results suggest that the decreases in tumor incidence and tumor weight may be related to the increase in plasma and tissue levels of beta-carotene as a result of feeding high levels of beta-carotene.