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Less than one-third of the advice dispensed on TV’s popular “The Dr. Oz Show” can be backed up by even modest medical evidence, researchers found.

If that sounds alarming, consider this: Nearly 4 in 10 of the assertions made on the show appear to be made on the basis of no evidence at all.

The researchers who fact-checked Dr. Mehmet Oz and his on-air guests were able to find legitimate studies related to 11 percent of the recommendations made on the show. However, in these cases, the recommendations ran counter to the medical literature.

“Consumers should be skeptical about any recommendations provided on television medical talk shows,” the researchers wrote in a study published last week in The BMJ, formerly The British Medical Journal. “Viewers need to realize that the recommendations may not be supported by higher evidence or presented with enough balanced information to adequately inform decision making.”

Critics of Oz, an accomplished cardiac surgeon with degrees from two Ivy League universities, complain that his show is little more than an hourlong infomercial for weight-loss fads such as green-coffee-bean extract. (The Federal Trade Commission has sued the company that hawks this product.) A spokesman for the Center for Inquiry accused him of selling “snake oil.”

In June, a Senate subcommittee took him to task for telling viewers (who number 2.9 million on any given day) things such as: “I’ve got the No. 1 miracle in a bottle to burn your fat. It’s raspberry ketones.”

“I don’t get why you need to say this stuff because you know it’s not true,” Sen. Claire McCaskill, D-Mo., said during the hearing.

A group of physicians, pharmacists and other researchers from Canada had its own questions about programs such as “The Dr. Oz Show.” So group members set out to see whether the “skepticism and criticism from medical professionals” were warranted.

The Canadians focused on “The Dr. Oz Show” and “The Doctors,” another daily talk show that averages 2.3 million viewers a day. After watching two episodes of each program, they hypothesized that only half of the claims made on the shows could be supported with evidence. They also calculated they would need to review 158 specific recommendations to see whether their hypothesis was correct.

Lucky for them, the shows are rife with recommendations — 12 in a typical episode of “The Dr. Oz Show” and 11 in an episode of “The Doctors.” So members of the research team watched 40 episodes of each show that were randomly selected among all the episodes that aired in the first five months of 2013.

They found that 32 percent of the 479 recommendations made on “The Dr. Oz Show,” either by the host or his guests, fell under the heading of “general medical advice.” An additional 25 percent of the claims were about dietary topics (i.e., foods that boost the immune system) and 18 percent were about weight loss.

On “The Doctors,” 66 percent of the 445 recommendations were about “general medical advice,” 9 percent were about dietary topics and 8 percent were about weight loss. (Other categories included exercise, alternative therapies and cosmetics.)

Among all of these recommendations, the researchers randomly selected 80 from each show and looked to see what evidence, if any, could back them up. Two team members conducted independent searches. “In an attempt to be as fair as possible” to the shows, they wrote, they “used a relatively broad definition of support.”

And yet only 21 percent of the recommendations on “The Dr. Oz Show” could be supported by what the researchers considered “believable” evidence. An additional 11 percent were supported by “somewhat believable” evidence.

The recommendations made on “The Doctors” were more credible: 32.5 percent were supported by “believable” evidence and 20 percent were backed by “somewhat believable” evidence, the researchers found.

Good or so-so evidence contradicted, on average, 11 percent of the claims made on “Dr. Oz” and 13 percent of the claims made on “The Doctors.”

Researchers also found there was no relevant medical research for 39 percent of Oz show recommendations and none for 24 percent of “The Doctors” recommendations.

Neither Oz nor the team behind “The Doctors” could be reached for comment.