A new study from the British Journal of Medicine has found that about two-thirds of world-famous snake-oil salesman Dr. Oz’s medical recommendations can’t be backed up with scientific evidence.

The study, which used episodes of both The Dr. Oz Show and The Doctors, involved researchers watching 80 episodes (40 of each) and examining the medical recommendations within them.

They identified 479 recommendations from Oz and 445 recommendations from The Doctors. Those were then narrowed down to 80 randomized recommendations, which were then compared to existing medical literature and practices.

Researchers found that just 33 percent of Dr. Oz’s medical recommendations were supported by believable or somewhat believable evidence; those coming from The Doctors were supported 53 percent of the time. They also “found believable or somewhat believable evidence against 11 [percent] and 13 [percent] of the recommendations on The Dr. Oz Show and The Doctors, respectively.”

Dr. Oz also never explained what the benefits were to the advice he was giving about 58 percent of the time. Apparently he thinks that people should just listen to him because he has a title in front of his name and is on television.

The study also said that for “slightly over 1 in 3 and 1 in 4 of the recommendations for The Dr. Oz Show and The Doctors respectively, no evidence could be found,” despite the researchers “being quite liberal in the type and amount of evidence” they required.

“Consumers should be skeptical about any recommendations provided on television medical talk shows,” researchers concluded, “as details are limited and only a third to one half of recommendations are based on believable or somewhat believable evidence.”

Noting that health care decisions are “often challenging,” the scientists said that viewers need to realize that not everything the TV quacks recommend is backed up by medical fact, and that “patients would do well to ask healthcare providers specific questions about the benefits and harms, along with the magnitude of the effect … and costs and inconveniences of any recommendations.”

Listen to the researchers discuss this study on their Best Science Medicine podcast.