Effects of Japanese kelp (kombu) on life span of benzo[a]pyrene-fed mice.

The prolonging effect of Japanese kelp (kombu) on life span was investigated in mice fed a diet containing the carcinogen benzo[a]pyrene (BaP). Three groups of six mice each were fed a normal diet with 0, 2 and 5%, kombu powder, while another three groups were fed those diets with 4 ppm BaP loading. The 2 and 5% kombu diets did not affect life span compared to the control group given 0%, kombu. BaP significantly reduced the life span. Addition of 2 or 5%, kombu to the BaP diet remarkably recovered the life span to a level similar to that of the control. The feces of the 2 and 5% kombu groups contained 6.9+/-1.2 and 16.8+/-1.8% of the ingested BaP, respectively, mainly in forms adsorbed on kombu fibers. The BaP-alone group given cellulose as dietary fiber instead of kombu, did not show any such effects. Humans are exposed to various environmental carcinogens such as BaP, and kombu fibers probably contribute to longevity by removing them.