Chemoprevention by the Oxygenated Carotenoid β‐Cryptoxanthin of N‐Methylnitrosourea‐induced Colon Carcinogenesis in F344 Rats

β‐Cryptoxanthin (βCx), one of 4 major carotenoids in the blood, was investigated for anticarcinogenic activity in F344 rats. Four groups of 25 rats each received an intrarectal dose of 2 mg of N‐methylnitrosourea 3 times a week for 5 weeks, and were fed the diet supplemented with 0 ppm (control), 25 ppm, 5 ppm or 1 ppm βCx throughout the experiment. The colon cancer incidence at week 30 was significantly lower in the βCx (25 ppm) diet group, but not in the βCx (5 ppm) and βCx (1 ppm) diet groups, than in the control diet group: 68%, 84%, 80% vs. 96%. The results suggested that dietary βCx may affect colon carcinogenesis after accumulation in the colonic mucosa, perhaps due to absorption from the colon as well as the small intestine.