Dr. Mehmet Oz is as famous as a TV doctor can be, but he’s not always well-known for getting his facts right—especially about sweeteners. The Great Oz recently hosted Dr. Robert Lustig on his show (we wrote about him Tuesday), and his bottom line was a flat-out rejection of the idea that “a calorie is a calorie” no matter what food it’s in. No, says Oz, certain foods and everyday things are full of so-called “obesogens”—chemicals that are secretly making us fat. Specifically, Oz warns his audience about farmed salmon, high fructose corn syrup (corn sugar), and canned veggies.

This theory was equally silly the first time it because famous. Back then, it used the buzz-word “endocrine disruption.” The basic (crackpot) idea is that chemicals in foods (and from food packaging) mimic hormones that the human body produces, messing with our organ systems’ ability to function normally. Clever theory, but woefully lacking in facts. As The Wall Street Journal’s Allysia Finley reported a few months ago:

Chemist Joe Schwarcz at McGill University's Office for Science and Society notes that the doses of these chemicals found in food are likely too low—we're talking in millionths of grams—to have a material effect. "Every day people are exposed to hundreds of thousands of natural and artificial chemicals which would show very similar effects if run through these sensitive tests," he says. Even the sugar fructose, which naturally occurs in fruit, and genistein in soy show obesogenic effects when tested in rodents.

All of this helps explain why the National Toxicology Program reported in 2008 that "there is currently insufficient evidence to conclude that bisphenol A exposure during development predisposes laboratory animals to develop obesity or metabolic diseases such as diabetes, later in life."

So much for Dr. Oz’s claims about food cans and fructose.  And let’s not forget that the European Food Safety Authority determined (just last week) that there’s no need to lower the acceptable limit on one particular chemical whipping boy.

So what about farmed salmon? A guest-contributing doctor on Oz’s own website writes elsewhere: “Several studies have also shown that farmed salmon accumulate more cancer-causing pesticide residues than wild salmon. However, these studies fail to make a strong case that eating farm-raised fish poses a significant safety concern.” [Emphasis added.]

Technology has progressed to the point that you can find chemicals in microscopic levels (think: parts per billion or trillion) in just about everything. But it’s the dose that makes the poison. Detecting something doesn’t make it harmful. After all, even Vitamin C can kill you in high enough amounts.

Dr. Oz’s advice is for people to buy wild salmon. That’s fine if, like the good doctor, you can afford it. (Fish is heart-healthy, after all.) But as TIME writer Josh Ozersky recently noted, there are other “sustainability” issues in play—human ones:

[T]he fact is that, whether through DNA modification, artificial insemination, antibiotics or any other technique, high-tech aquaculture is the only way to save the planet's marine life…. If fish can be bred in hatcheries on a commercially viable scale, it will help stave off a food-scarcity crisis larger than any the world has ever known. So it might be in our interest not to scoff and sneer quite so reflexively.

Got that, Oz?