Modulation of N-nitrosomethylurea-induced mammary tumor promotion by dietary fiber and fat.
A test of the anticancer effects of dietary fiber was conducted using the N-nitrosomethylurea (NMU)-induced rat mammary tumor model. Starting 3 days after NMU treatment, four different groups of F344 rats (30 rats in each group) were fed as follows: Group 1 received a high-fat diet; group 2, a high-fat plus fiber diet (soft white wheat bran, 10% wt/wt); group 3, a low-fat diet; and group 4, a low-fat plus fiber diet. The rats remained on these diets for 15 weeks. Tumor incidence in group 1 was 90% compared with 66% in group 2 (P less than .001). Tumor incidence in group 3 was 63% compared with 47% in group 4 (P greater than .4). These results show that supplemental dietary fiber exerts an inhibitory effect on the promotional phase of NMU-induced mammary carcinogenesis in rats when fed a high-fat but not a low-fat diet. To test whether fiber may exert its antipromoting effect by reducing circulating estrogens, serum 17 beta-estradiol was assayed. No changes were observed in serum 17 beta-estradiol levels among the four groups, suggesting that the protective effect of fiber in this animal model is not mediated by a fiber-induced reduction of circulating 17 beta-estradiol.
Cohen
L A
LA
Division of Nutrition and Endocrinology, American Health Foundation, Valhalla, NY 10595.
Kendall
M E
ME
Zang
E
E
Meschter
C
C
Rose
D P
DP
D000818:Animals; D001835:Body Weight; D002606:Charcoal; D003911:Dextrans; D004041:Dietary Fats / Q000008:administration & dosage* / Q000009:adverse effects / Q000494:pharmacology; D004043:Dietary Fiber / Q000008:administration & dosage* / Q000009:adverse effects / Q000494:pharmacology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000097:blood; D004967:Estrogens / Q000097:blood; D004971:Estrus / Q000097:blood; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000097:blood / Q000139:chemically induced / Q000517:prevention & control*; D008770:Methylnitrosourea; D011374:Progesterone / Q000097:blood; D011863:Radioimmunoassay / Q000379:methods; D051381:Rats; D011916:Rats, Inbred F344; D014316:Tritium
D003911:Dextrans; D004041:Dietary Fats; D004043:Dietary Fiber; D004967:Estrogens; D014316:Tritium; D002606:Charcoal; D011374:Progesterone; D004958:Estradiol; D008770:Methylnitrosourea