Fibre content. If I'm correct with what I learnt at school fibre has very little dietary use other than to "lubricate" the intestines and allow food to pass easier without damaging the walls.. That's why too little fibre is the main cause of diverticulitis.....
Not just the liquid - drinking doesn't give you the trots I don't think... Unless maybe it's a fruit juice your drinking that has fibre in it..
Maybe I'm wrong..