[datavirtue]

Soybean oil is one prominent and very prolific and profitable example. It is everywhere. It was first developed to add to feed to fatten animals (turkeys). You can still buy it in fifty gallon drums at feed mills. Nasty stuff. It breaks down and oxidizes readily under heat (and in the body). Oxidation == free radicals. Hydrogenation (hydrogen injection) makes it thick at room temperature, otherwise it is a thin oil like any other vegetable oil you might be familiar with.

Very fattening, no nutrient value. Unless a restaurant is willing to invest in peanut oil (and they will tell you on the menu if they did because it costs so much more than hydrogenated soybean oil) all fried foods are cooked in burnt up (oxidized and broken down) soybean oil. You have to c he ange the oil in a fryer every day to get a decent food product out of it. Good restaurants might filter it and reuse it for one additional shift/day. In reality it is used until it is smoking heavily and not able to cook food without rendering it deflated and dark brown.

There are massive inertia and industry lobbyists (producers and food mfg) behind it that know how to install fear in politicians. We have know for along time that putting it in your body is a bad idea.

[Delk]

Canola oil, some seeds and (true) nuts, as well as fatty fish also contain lots of polyunsaturated fats. Most of those are generally considered healthy. Would those also become unhealthy for the reasons you've listed?

I think arguing that "polyunsaturated fats will be seen as grossly unhealthy" requires more than an example of (ab)use of a particular oil.

[colordrops]

Yes, they're all heavily processed in refineries using noxious chemicals, they have low smoke points, and get rancid easily. They are not a type of oil (omega-6 [1]) that humans have eaten much of until recently. We mainly got our source of them from food rather than pure oil.

Omega-3 polyunsaturated fats are good for you in moderation if extracted cold without processing, uncooked, and stored in opaque containers in a fridge.

In general, getting oils from foods is best, rather than using them in refined form.

The reason PUFAs are pushed so much is probably due to heavy support from the farms and industry that manufacture them.

[1] https://www.mayoclinicproceedings.org/article/S0025-6196(13)...

[Delk]

I don't claim to have any expertise in this matter. I suppose it's quite possible that the common understanding of "PUFA good, SFA bad" is flawed somehow. I'm not sure I agree with your arguments, though.

> they're all heavily processed in refineries using noxious chemicals

While processing might matter, it's hard to tell just from that if it does. Admonishing processing with "noxious chemicals" sound a lot like suggesting that something is healthier because it's natural.

> they have low smoke points, and get rancid easily

I can see these as detriments or even show-stoppers for some uses, but I fail to see how these are important if you don't overheat the oil or let it go rancid. I see these more as issues of incorrect use. In some sense they are of course downsides of the product since some other fats might have better properties in terms of ease of use (harder to overheat), but I don't think it follows that they're unhealthy by themselves. They could be, but that doesn't follow from a low smoke point.

As for omega-6 fatty acids, I've understood there to be some evidence that they're not healthy in large amounts, so there might be some truth to (at least some) polyunsaturated fats not being as healthy as they're made out to be. I still don't really see enough here to get behind the statement that polyunsaturated fats will be seen as grossly unhealthy in the future.

I might be wrong -- again, I have no expertise here -- but I just don't see it in the arguments.