Vitamins are very tiny molecules, says Bodanis, "so the portions don't really have to be as big as what's handed out now. Yet who would believe in the power of tiny pills?" he asks.
So "they're bulked up" with fillers that include sand, chalk and talc, bound by steamed extracts from pigs' feet and other animal bones, Bodanis says in his book The Secret Family.
And, he adds, "About half of the most popular vitamin pills stay in such large granules that they can't be digested at all."