Many of us know not to flush old prescription pills and medications down the toilet, since pharmaceutical drugs can contaminate our water supply. But according to the Food and Drug Administration, you should also avoid disposing of old vitamins and herbal supplements this way. They, too, can contaminate our water supply and cause what they call "safety risks." Instead, mix old vitamins with coffee grinds and use a nonrecyclable container to dispose of them. You can also give a few multi-vitamins to household plants; they'll thrive from the nutritional boost.