>>Have not checked new stuff, but my take on things was that refined sunflower oil was best for steaks, as it allows high temperature without adding too much of another taste.

Yep, that's the smoke point: https://en.wikipedia.org/wiki/Smoke_point Some oils have a smoke point not far above 100C (around 230F) meaning they're denaturing and producing toxins during most cooking while others such as avocado oil have smoke points 270C-300C (530F) as well as other redeeming features such as Vitamin E. Various refined oils have smoke points over 200C but refinement has a question mark in nutrition circles as it usually involves chemicals and bleaches.

Interestingly, other oils that can be pressed rather than chemically extracted can have very high smoke points. E.g. good quality pressed olive oil has a smoke point well over 200C without chemicals or refinement processes. There's lots of "extra virgin" olive oil (meaning extracted by pressing only with no chemicals) out there, but it's worth finding and paying more for a boutique version if you can find it since some of those can have smoke points that match avocado.

Anyway, the new evidence is that most vegetable oils including the various refined varieties are releasing these aldehydes during cooking. Animal fats and pressed olive oil appears not to release as many aldehydes. In the tests, cooking with some vegetable oils released over 100 times as much aldehyde as the recommended upper limit. Butter, despite a relatively low smoke point, appears to have far lower levels.

Another issue is Omega 6 vs Omega 3 fatty acids, with mutterings that the high Omega 6 level boasted by some oils is displacing Omega 3 to the detriment of health. Omega 3 tends to be higher in animal fats and Omega 6 higher in the likes of corn oil.

The other one to watch is the acrylamides that always seem to be released whenever starchy foods are fried or cooked at high temperature.

Sometimes it seems that everything you eat is a health risk! However, IMHO a rational response in this case is to use pressed avocado oil for frying or cooking at 200C or over and to keep using the good pressed olive oils for salads and dressings. If cost is an issue, butter also works for cooking and usually is cheaper though it pays to inspect the label to ensure it's not processed or mixed with water, oil or anything else. Lard is not the sort of thing you find in supermarkets these days. ;-) Oh, and don't forget the red wine. ;-)