There are a LOT of problems with multivitamins in my opinion. For example, every multivitamin is different but one wouldn't think that they were. So we go to WalMart and we stare at the 15 kinds of multivitamins because our doctor told us to take one. And we think, "Uh, what's the difference?" So we grab the cheapest one or the one we saw a commercial for on TV recently and we head on our way. Is it quality? Does it contain what it says it does?
And we start taking our multivitamin and ignore all the advice from people on this forum saying, "vitamin B12, vitamin D, etc" because we're on a multivitamin, we're covered. Or we understand that we need to take thousands of IUs of vitamin D separately from our multivitamin and we do so and don't experience any benefit and wonder why, not knowing that our multivitamin is packed full of a form of vitamin A called retinol which is shown to interfere with vitamin D. Or the multivitamin has high levels of folate which are now masking the symptoms of the person's vitamin B12 deficiency and they're well on their way to permanent damage. I could go on like this all day and I still know relatively little in the grand scheme of things. Vitamins and minerals are so incredibly complex. And there are no doubt interactions and variables that science has no clue about.
We're dealing with an inflammatory disease where malabsorption, nutritional deficiency, drug interactions and chronic diarrhea or constipation are common. It's just plain flat out not as easy as telling someone to take a multivitamin and calling it a day. We need to be monitored for specific deficiencies and then properly supplement based upon those results. Why supplement for something we're not deficient in and risk interactions? We need to stop bringing a shotgun to a battle where a sniper rifle would work best.
It's not my place to say not to take a multivitamin and I could very well be wrong and the benefits far outweigh the negatives. But monitoring of specific vitamin levels and just supplementing what is needed may be something to discuss with your doctor or dietician.