Somebody's $25 billion dollar industry is likely to get a lot smaller once people realize that they're throwing their money away on vitamins. This could send shockwaves through the retail world as well--entire sections of stores are planned around vitamin supplements and displays, to say nothing of the health food industry.
Taking vitamins is an ingrained habit that reinforces positive self-identity. Reversing this could take decades. Of course, once people hear something sponsored by the vitamin industry to counteract this assault, well. You'll be living in a world full of confusion and plastic bottles.