I go out of my way to eat all sorts of green leafed veggies that will be high in iron and calcium, (including but not restricted to spinach, I actually try to avoid oxalic acid which is in that ) specifically because I expect that diarrhoea will play havoc with those nutrients, and I eat sunflower and pumpkin seeds till they come out of my ears, because of the nutrients they contain. Does that count ? I've never actually heard of the sunflower and spinach thing.
For what it is worth, my problems with diarrhoea are much less than most folks on this board - my problems tend to be fatigue oriented.
But I don't know if that is just luck.