Among the Winfrey guests who have offered questionable medical advice:
* Suzanne Somers: She told Winfrey she swallows 60 supplements every day and takes a variety of bioidentical hormones to fight aging.
* Jenny McCarthy: Declaring that vaccinations caused her child's autism, the actress supported a Winfrey guest who said she wouldn't get her own kid vaccinated.
* Physician/author Christiane Northrup: She told Winfrey viewers that "in many women, thyroid dysfunction develops because of an energy blockage in the throat region, the result of a lifetime of 'swallowing' words one is aching to say."
Winfrey insists she is only trying to open dialogue between her viewers and their doctors.
"For 23 years, my show has presented thousands of topics that reflect the human experience, including doctors' medical advice and personal health stories that have prompted conversations between our audience members and their health care providers," Winfrey says in a statement. "I trust the viewers, and I know that they are smart and discerning enough to seek out medical opinions to determine what may be best for them."
But some Winfrey viewers say they have a hard time not taking the daytime diva's information to heart.
Living Oprah, a blogger who spent an entire year following "the advice of Oprah Winfrey," said she "had mixed results from the health guidance I learned on Oprah's show and there were a couple items that conflicted with my own doctor's guidance. My doc always shrugged at how many supplements I knocked back in 2008, for instance."
Biologist PZ Myers, an associate professor at the University of Minnesota, also blogged: "It's about time one of the big media players pointed out that she is promoting dangerous fake therapies ... all with a happy smile, of course, and a message of positive self-esteem for women. It's still credulous glop, though."