My comment is that it is not ONLY low fiber diets. There are a lot of other risk factors involved. Will high fiber help - absolutely. Is it the be all end all - no I doubt it.

Western diet collapsed its fiber intake well over 80 years ago - it would have shown up already.

> My comment is that it is not ONLY low fiber diets.

Well, you said "can't" and I asked "why", which feels very reasonable to me. Your argument seems to be that it wouldn't account properly for the data - specifically, you're saying we would have seen colon cancer rates rise earlier.

> Western diet collapsed its fiber intake well over 80 years ago - it would have shown up already.

I don't really buy this for a lot of reasons. Probably the two most important are (a) ability to screen historically and (b) the timing isn't particularly "off" for the fiber argument. We did see it already, we've been seeing increases in color cancer risks for decades.

Now, I'm not married to it "just" being fiber whatsoever, but if I were to "bet" on the major contributing factor, naively, that's where my money would go. I think it's very reasonable to not place your bet there.