I recently went for my yearly checkup with my gastroenterologist...had several surgeries years ago for divertic.
Anyway, had dropped off a stool sample a few weeks earlier as part of the routine tests he does. In his office after reviewing the usual stuff he asked me how many vitamins do I take daily. And I told him and asked why? He smiled and said the stool sample had several intact, that had never dissolved at all. He said he sees this over and over with patients. Tablets are very hard for the tract to break down fully and of course are then not absorbed and doing you no good at all. Not to mention the serious waste of money, vitamins are pricey.
I asked him what is the best alternative and he suggested buying your vitamins in capsule, not tablet. Capsules are the clear plastic with power inside which are easier for the system to deal with. Since I take individual vitamins, (C,D,E,etc.) these are easy to find. But you can't find a multi in this form, at least not that I could find.
So if you are taking vitamins tablets, especially those big horse pill type, chances are you are not digesting these.
Please consider the capsule form and take them individually.