Just a quickie,
It has come up off blog on a number of occasions that inulin, a fructose polymer completely indigestible to humans but edible by bacteria, is a potential carcinogen. Couple of refs here and here. I was a bit dubious of this model as it showed beef to be carcinogenic too. That upsets my biases!!!! And slightly odd as this different model showed bacon, yes you read that correctly as bacon, to be protective. Beef and chicken were neutral in this chemical carcinogen based model. I decided that playing with mice, especially bowel cancer prone mice like ApcMin/+ engineered mice, might say relatively little about humans. Still not sure.
Now this dropped out of Pubcrawler today. If you are a ApcMin/+ mouse you can choose you carcinogen from wheat bran or apple pulp (that's the healthy fiber from healthy fruit, apples):
"In conclusion, both types of resistant carbohydrates increased polyp number and tumour burden and this was associated with elevated epithelial cell proliferation and crypt fission."
Because my access account doesn't allow me the full text I can't see what the fiber did to the wild type control mice. Always the most interesting bit and not in the abstract.
Crypt fission is bad, it's what wheat germ agglutinin and insulin do. Looks like all sorts of fiber do too. Just an extreme mouse model, but next time someone extolls their belief in the benefits of resistant starches or fiber, maybe they should read and think!