Setting aside Trump, I have no idea why people who can apparently be mostly reasonable about, say, cars subscribe to utterly batshit insane views about diet and health and buy into all kinds of snake oil.

I'm not saying that there's no magical thinking with cars

"my magical fuel additive" or whatever

but I have seen more utterly insane stuff regarding what someone should eat or how to treat medical conditions than in most other areas.

It's also not new. You can go back, and find people promoting all kinds of snake oil when it comes to health. Some of my favorites are the utterly crazy stuff that came out when public awareness of radiation was new, and it was being billed as a magic cure for everything.

I get that not everyone is a doctor or a dietician. But you'd think that any time you see someone promoting something as a fix for a wide, unrelated range of conditions, that it should be enough to raise red flags for someone, layman or no.