Olives are fruits, not seeds, and their oil is fine in non-pathological quantities.  "Light" olive oil is suitable for cooking, but not frying or sauteeing (I use coconut oil or clarified butter).  Extra-virgin olive oil should not be cooked with.  As Paul said, it's a matter of stability at heat.

MCT oil is made of Medium-Chain Triglycerides, and they're extracted from coconut oil.  I use it occasionally when I need a fat that's liquid but completely tasteless: the problem with butter, tallow, and coconut oil is that they're solid at room temperature, and are therefore unsuitable for salad dressing or other cold dishes.  And some things just don't taste right when made with olive oil...

JS

It comes down to the stability of oil at heat and it should be noted that some animal fats also become unstable at high heats such as roasting in the oven. "Smoke point" is a useful ballpark figure but for a more thorough look at oxidative stability of fats, check out "Rancimat analysis".

That's a good question!  High-oleic sunflower oil will contain less hidden trans-fat than regular sunflower oil, because it's got less linoleic acid to begin with (less than 20%, versus 50-75%).

I still don't like using processed seed oils for other reasons, including high linoleic acid content.  Personally, I tend to use light olive oil for my own mayonnaise, hollandaise, etc. -- and I've started mixing it with MCT oil to make it even lighter on linoleic acid and heavier on MCTs (which have their own health benefits). 

Careful with the MCTs, however...too much tends to flush out the system, if you know what I mean.

JS

I'm curious about high oleic sunflower oil. I have been using it to make mayo.

I wrote that article, too!  (About rumenic acid and the various isomers of CLA.)  Link: "Trans Fat Is Good For You, But Only If It's From Meat And Butter."

JS

"What Should I Use Instead?... Butter, beef tallow..."

🙂

Yes, now that the dangers of trans fats are more well-known and labeling is legally required, many places don't deep-fry in hydrogenated oils anymore.  Of course this means the oil oxidizes and goes rancid much more quickly, which isn't healthy either!

Unfortunately, most Americans get a lot more than 5% of their calories from "vegetable oils", most of which are much higher in linoleic acid than canola.  LA provides close to 10% of energy in the American diet, if I recall correctly, due to the prevalence of corn, soybean, sunflower, and safflower oils.  And since that's an average, trans fats become a meaningful percentage for many.

JS

First, the 2% doubling your risk for heart disease was based on your total caloric intake. That means that if you ate nothing but canola oil, which is 1-3% trans fats, your chance for heart disease would double.

The percentage of trans fats you get from canola oil is actually the percentage of trans fats in canola oil multiplied by the percentage of calories in your diet you get from canola oil.

So if Canola oil makes up 5% of the calories you get for the day, your level of trans fats would be (.05*.02)=.001=0.1%, which is considerably lower than the 2% that doubles your risk of heart disease. It's still a factor, but it's an order of magnitude smaller one than what you indicated.

Second, I've worked at two different fast-food restaurants, and the oil for the fryers in both places were carried in plastic jugs in liquid form. That means the oil is not partially-hydrogenated, because if it was it would probably be transported in solid form due to the longer shelf life of partially hydrogenated oils.

Linoleic acid is indeed "essential" -- but in such minute quantities (milligrams) that it's basically impossible to not get enough by eating food.  Even the lowest of low-fat diets (e.g. McDougall, Ornish) get you to about 10% fat just from the intrinsic fat content of grains, beans, fruits, and veggies.

It was only discovered that it was possible to become deficient in linoleic acid once hospital patients started being fed intravenously with zero-fat diets of purified "nutrients".

I'm not sure if you're properly representing Michael Pollan, but if so, he's wrong in this case.  There is extensive research on omega-6 intake, and eicosanoid biochemistry is relatively well understood: the idea of consuming less omega-6 and more omega-3 in order to decrease systemic inflammation is a fact, not a "fad".

JS