The October 15 issue of the New England Journal of Medicine features a perspective article on contaminated dietary supplements. Dr. Pieter Cohen reports that the FDA has discovered more than 140 contaminated products, but these represent only a fraction of the contaminated supplements on the market. He further notes that "The regulatory environment for dietary supplements is poorly understood by both consumers and physicians."
http://healthcarereform.nejm.org/?p=2017&query=home