Many new supplement ingredients are introduced without any regulatory oversight.
Americans spend more than $28 billion annually on vitamins, minerals, herbals and other "natural" products in the form of dietary supplements. They do this assuming they are safe and effective. The FDA regulation of these products has been rather weak, even though the Dietary Supplement Health and Education Act requires manufacturers to present "reseasonable expectation of safety." The food industry is held to much more stringent safety standards than the supplement industry. The New England Journal of Medicine has an informative article on this by Pieter Cohen, MD of the Cambridge Health Alliance.
PositiveTip: Remember--not all things "natural" are safe or effective!