He has warned parents that apple juice contained unsafe levels of arsenic, advice that the Food and Drug Administration called “irresponsible and misleading.” In 2013, he warned women that carrying cellphones in their bras could cause breast cancer, a claim without scientific merit. In 2014, the British Medical Journal analyzed 80 recommendations on Dr. Oz’s show, and concluded that fewer than half were supported by evidence.

Two researchers who worked on “The Dr. Oz Show” for a year during a break from medical school in the 2010s said in interviews that the show’s producers had originated most of its topics, often getting their ideas from the internet. But the researchers, whose job was to vet medical claims on the show, said that they had little power to push back, and that they regularly questioned the show’s ethics to one another and discussed quitting in protest.

“Our jobs seemed to be endless fighting with producers and being overruled,” said one of the former researchers, both of whom are now physicians and insisted on anonymity because they said they feared that publicly criticizing him could jeopardize their careers.