But Charlap noted that while some studies suggest milk thistle may be helpful for people with liver disease, the evidence is unclear on its other health benefits. So when a woman on milk thistle came into Charlap's clinic for her annual wellness visit, he asked if she had any problems with her liver, an abnormal liver-function test, or any other medically justifiable reason for using the product. The answer was no: She used milk thistle because her "other doctor" told her to do so. She was taking Oz's medicine.
Oz, Charlap noted, has also encouraged people to take two baby aspirin every night before bed to prevent heart attacks. For people at high risk for coronary heart disease, the authoritative U.S. Preventive Services Task Force would agree with him. But for healthy and older folks, aspirin can have damaging side effects — including bleeding ulcers — which are well-documented and may outweigh any potential benefits. Aspirin can also hurt patients who are on anti-coagulants or who have a history of gastric or stomach ulcers, a warning Oz does not mention on his show. An exasperated Charlap asked: "Where is the 'first, do no harm' when he does something like that?
Beyond potential damage to people's health and purses, this kind of peddling can also foster doubt and mistrust of science. As Edzard Ernst put it: "Prominent people like Oz do have considerable influence. If this influence is used to promote quackery, bogus treatments will seem credible. Using bogus treatments for serious conditions may cost lives."
So how are we supposed to tell medicine from miracles? As a general rule, said Victor Montori, an evidence-based medicine guru at the Mayo Clinic, "If studies are cited, then this cannot be, at the same time, a secret revealed just to you now. If the studies are any good, the effects are usually very small." Referring to Oz's holiday weight-loss advice, he added: "It is very unlikely that an important compound hidden in the garcinia could have a big effect."