>  and I thought that they had a lower cancer
> rate than the "civilized world".
>
I don't think this is true. Cancer seemed pretty common at least in
Guatemala where I worked. The basic diet, three times a day was beans
and corn tortillas. People tended to die young from all kinds of
causes, there were few really old people. This might make it seem as if
cancer is low there, since most cancers occur in very old age. There
were lots and lots of parasites!

Every one has "parasites" of some kind or other, but the big nasty ones
are pretty rare in places with purified water.