No data. Period.
are marketed by manufacturers w/o any requirement by fda
or other 3rd party to prove safety and/or effectiveness prior to marketing.
In other words, companies are allowed to say whatever they want to convince you to buy their products. Check out 2 recent news articles: http://goo.Gl/bbmdcw (usa today) & http://goo.Gl/uilodl (fda via nbc) re lack of oversight & contamination.