I completely forgot about sugar alcohols!

Sugar alcohols were generally only available in ready-made products like chewing gum and sugar-free candies and cookies back in the 70's, although back then they had some sugar alcohols in some brand of sugar substitute packets that I used in baking. (I keep thinking it was sweet'n'low, but can't find confirmation that brand ever included sugar alcohols)

It took me quite a while to figure out that the sugar alcohols were what was causing my random bouts of diarrhea. (if it had only been gas, it would have still been a problem, just not quite as bad of a problem)