Did you read the title?  This is the exact reason I recommend eating a diet filled with REAL FOOD, and taking only a few specific supplements that are required for normal function in the human body!  Choose whole food vitamins over synthetic (click here to see the brand I use). Here is a great quote from Dr. Natasha Campell-McBride, author of Gut and Psychology Syndrome to explain more:

“There has been an interesting experiment performed in one of the food laboratories. They analyzed the nutritional value of some brands of cereals and the paper boxes in which these cereals were packaged. The analysis showed that the box, made of wood pulp, had more useful nutrients in it than the cereal inside. Indeed, breakfast cereals have got very low nutritional value. To compensate for that the manufacturers fortify them with synthetic forms of vitamins, claiming that by eating your morning bowl of cereal you will get all your daily requirements of those vitamins. Well, the human body is not that simple; it has been designed to recognize and use natural vitamins, coming in natural food form. That is why synthetic vitamins have a very LOW absorption rate, which means that most of them go through and out of your digestive tract without doing you any good. Then, whatever amount of those vitamins does get absorbed is often not recognized by the body as food and gets taken straight to the kidneys and excreted in urine. We have a new syndrome in our modern pill-popping society – a syndrome of expensive urine.”