I have carefully avoided having any opinions about Jordan Peterson, the quasi-mystical self-help guru and anti-PC YouTube star, because you can’t voice any sort of take on him without immediately taking up arms in the culture war. But now he’s sort of grabbed my attention, via his daughter — and his diet.

Peterson Sr has, I learn, claimed a few times that eating nothing but beef, salt and water has rid him of depression, anxiety,  gingivitis, and, apparently, snoring. He got the idea from Mikhaila, his daughter, who had a variety of childhood health problems — rheumatoid arthritis, depression, “idiopathic hypersomnia” — which, she says, all cleared up after she started eating nothing but beef and water (and vodka and bourbon). She calls it the ‘Lion Diet’, and for just $599 a year you can sign up for live videos and meetups talking about how to do it. (Spotter’s badge to Ben Sixmith; previously I had only heard of her $120-an-hour Skype consultations.) A book about the diet, purportedly by the pair of them (Mikhaila says it isn’t), was recently the best-selling book on Amazon about “toxicology”.

My first concern, by the way, was that the Petersons would have died some time ago of scurvy, and I was going to suggest that someone go and check up on them. But apparently you can get reasonable amounts of vitamin C from raw or nearly raw meat, especially organ meat — the Inuit managed it for centuries. (Although, the Inuit apparently also have larger-than-human-average livers to assist with the breakdown of protein; it’s not clear that the Peterson family does.) So as long as the Lion Diet includes steak tartare, or beef kidneys, they’re probably still alive. (Still, if you’re in the neighbourhood, you know…)

Anyway. The elder Peterson sells himself as a purveyor of unvarnished truth, and the idea that he’d been cured of his mental and physical ailments by eating beef struck me as, shall we say, unlikely to be true. To explain why, I thought I’d start by talking about how hard it is to work out what is and isn’t good for you, diet-wise.

We read a lot of confident, specific claims about what is and isn’t good for us, but the actual evidence supporting them is usually patchy. Even apparently basic questions like “does red meat cause cancer?” are immensely vexed. There was a neat demonstration of that earlier this month when a group of scientists published a set of guidelines based on reviews of the evidence. They were looking at the same data that everyone else had looked at — including the WHO’s International Agency for Research on Cancer (IARC), which concluded that bacon was a carcinogen. The Department of Health and Cancer Research UK also say that you should eat red meat sparingly, because it raises your risk of colorectal cancer.

But the new advice came out and said, according to media reports, that this was all nonsense and you should eat as much red meat as you like.

It was, of course, more complicated than that. In fact, the new review found that there was an increased risk from eating bacon, just that in absolute terms it was small (very roughly, between 1 and 18 new lifetime cases of cancer for every 1,000 people who eat an extra 90g of red meat a day). It is entirely in line with what CRUK and everyone else said. The new guidelines said that the uncertainty was huge, and that a lot of people enjoy eating meat, so the tradeoff might not be worth it; the WHO and so on didn’t take into account those tradeoffs, but simply looked at whether or not, on the balance of evidence, eating red meat would raise your risk of cancer.

Still: that’s the level of complexity we’re dealing with. Two groups of well-intentioned, intelligent experts can assess the same evidence, even arrive at broadly the same conclusions as to what the evidence says about the risk, and come out with entirely different advice about what you should do on the basis of that risk.

So when someone such as Mikhaila Peterson comes out with a faddish diet which they confidently say will make you healthier and cure your diseases and so on, I am immediately sceptical. Especially if they’re charging punters hundreds of dollars for it.

The Petersons are far from the only people to push daft diets; on Google you can see lists of “the seven superfoods” (fish, yoghurt, chocolate, nuts, olive oil, eggs, and blueberries, apparently) or “the 25 superfoods” (acai, avocado, bee pollen, cacao — I can’t face listing them all) and so on. The claim is that these particular foodstuffs are powerfully good for you in some health-giving way, beyond simply “eating your greens”.

But there isn’t much good research into it. It’s hard to do randomised controlled trials where you give 10,000 people avocado and 10,000 people some placebo avocado for 30 years and see who dies first. So the main kind of research is asking people what foods they eat, and seeing whether people who tend to eat more avocado tend to be healthier or live longer.

But first, that relies on people accurately remembering what they ate, which is not always the case; and second, it relies on the people who eat avocado being otherwise the same as the people who don’t. Obviously, in real life, that’s not the case: people who eat lots of avocado are likely to be very different — notably, richer — than the ones who don’t. And since richer people are more likely to be healthy, it’s very hard to be sure that avocado is causing the improvement. You can try to control for socioeconomic status and other factors, but in the end it’s very messy.

You could, perhaps, detect some enormous effect. The impact of smoking on cancer risk was discovered, essentially, like this — because loads of smokers got lung cancer and almost no non-smokers did. But no foodstuff has been found to do any such thing. Even the purported negative effects of specific elements (such as fat, or sugar, or red or processed meat) have, as in the case of bacon and cancer, been largely small, ambiguous, and contested. If eating meat-only diets had a huge effect, it would probably have been noticed in the same way that the smoking-cancer link was noticed; it hasn’t been.

Peterson Jr’s absurd assertions about her regime — “This Lion Diet that healed me works for everyone” — strongly remind me of claims made about other pseudoscientific fads that have sprung up. Disciples all think that whatever it is they’re campaigning against, be it red meat, WiFi radiation, insufficient water, or vaccines, is the cause of every disease, and that simply following some simple step (avoiding red meat, or not vaccinating, or turning off your router) will lead instantly to a healthy population.

Her Lion Diet is obviously nonsense. It is, though, at least symbolically interesting nonsense, since the leftist position is to eat more plants and less meat, for health, environmental and animal-concern reasons, and Jordan Peterson’s whole thing is constantly telling the Left (not always incorrectly, I should admit) that they’re wrong. So the Peterson family brand of pseudoscientific food nonsense is to go 180° in the other direction and eat only the most carbon-intensive form of sentient being they can think of.

There’s an irony here, really. In general, with diet, it’s essentially impossible to be much more specific than “eat everything in moderation, and eat your greens”, just like your parents told you. You’d think that Jordan Peterson of all people, king of the “tidy your room” brand of homespun wisdom, would be in favour of that old-school advice. And yet somehow, perhaps sincerely, perhaps to own the libs, he and his daughter have ended up pushing an all-meat diet that is every bit as stupid (and significantly more likely to make you sick) than any number of hippyish gluten-free vegan fads. I’d keep my $599, myself.