There was an interesting study published recently that I discussed in this posting. They found that fructose malabsorption occured with about equal amounts (48-55%) in IBS-C & IBS-D and about twice as often compared to IBS-A (24%).
IBSers with fructose malabsorption probably didn't hang around the board long because the EFI diet wasn't working for them. Image how many more might have stayed if fructose malabsorption in IBSers had be accomodated in the EFI diet