Americans are still hooked on taking supplements.
A new survey shows fewer people are taking multi-vitamins.
But about half of Americans are taking at least a single supplement.
Many of these products have little evidence to prove they help, but researchers say fancy ads promote their use.
"This creates a market for products that appear on store shelves, well-lit store shelves with friendly sales people, in which the products would appear to be checked out by the government, safe and effective, but in fact, might not have much evidence to back them up," said Dr. Pieter Cohen, Cambridge Health Alliance.