More than a quarter of posts on Facebook sites for people with diabetes are promotional in nature, many touting products unapproved by the FDA, according to an analysis of diabetes-focused social networks.

The study, published in the Archives of Internal Medicine, looked at 15 sites found through a Google search. The sites studied varied widely, with membership ranging from 3,074 to more than 300,000 and diverse policies on advertising, sponsorship and membership, though all but three – TuDiabetes.org, diabeticrockstar.com and thediabetesoc.com – featured industry advertising. Half of the sites featured advertising from drug companies, two-thirds from device manufacturers and another two-thirds ran ads for diet and exercise products, while 13% ran ads from insurers. Other sources of funding included foundation and industry sponsorship, Web host sponsors and donations.

All but two sites required commenters to register, though many required minimal information, some only asking users to provide a handle and an email address. Only one site, TuDiabetes, “required an extensive profile to be sent to the site administrator for approval.” Physicians were on hand to answer questions in a third of the sites and more than half the sites used diabetes educators to answer member questions, though those authorities systematically scanned posts on very few sites.

The study’s authors wrote ominously that “substantial efforts to gather data from Web site participants were noted,” and said “little is known about the structure of communication, the sources of funding and the presence or use of advertising on these sites.”

“Existing sites differ in their approach toward communication structure, authenticity and quality oversight, expert participation and advertising or sources of funding,” said the report. “These metrics may be important to patients when selecting a community and may be of interest to health care providers who ultimately may advise patients about their particular needs.”