An article on Forbes.com, titled POM Wonderful's Deception Is The Tip Of The Iceberg, outlines the ways in which deceptive health claims by corporations erode consumer trust in any kind of health benefit claim, and points to a source of the problem, the Dietary Supplement Health and Education Act of 1994 (DSHEA). From QuackWatch.org, an explanation of the DSHEA:
[The] DSHEA [...] defined "dietary supplements" as a separate regulatory category and liberalized what information could be distributed by their sellers. DSHEA also created an NIH Office of Dietary Supplements and directed the President to appoint a Commission on Dietary Supplement Labels to recommend ways to implement the act . The Commission's final recommendations were released on November 24, 1997 [5,6].
The Food, Drug, and Cosmetic Act defines "drug" as any article (except devices) "intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease" and "articles (other than food) intended to affect the structure or function of the body." These words permit the FDA to stop the marketing of products with unsubstantiated "drug" claims on their labels.
To evade the law's intent, the supplement industry is organized to ensure that the public learns of "medicinal" uses that are not stated on product labels. This is done mainly by promoting the ingredients of the products through books, magazines, newsletters, booklets, lectures, radio and television broadcasts, oral claims made by retailers, and the Internet.
Read the whole article. It's worth it.
The Forbes article explains why the problems that the DSHEA causes extend even beyond allowing questionable or dangerous materials onto the market:
All of this harms both consumers and brands. Consumers are not in a position to critically evaluate drug trials. For instance, many consumers do not consider the difference in credibility between small-scale manufacturer-sponsored studies and large double-blinded, placebo-controlled studies that are the medical community’s gold standard.
Faced with a barrage of sensational claims relating to everything from weight loss to impotence, we lose a measure of trust in all brands.
The marketing climate that the DSHEA creates puts us all in a position where we're less able to take care of ourselves or monitor our own health. Trying to get informed about medicine in the US is a constant struggle against illegitimate and misleading claims, designed to look as though they come from legitimate sources.
It's disturbing to know that there's a specific law in place designed to give companies a way into lying about what their products do. On the other hand, it's good to know that there's a specific target for change.