Avoid “vegetable” oils (seed oils)
common cooking oil in UK
soybean and corn oils
these oils are added to many processed/packaged foods, especially in USA
They are high in omega-6 polyunsaturated fatty acids, which when consumed in excess (especially relative to omega-3 from fish oils) are reported to promote inflammation.
In Western countries like UK and USA, we consume far more omega-6 than omega-3 fats, due to a diet high in added vegetable oils and low in oily fish.
The “ideal ratio” of omega-6-to-3 in the diet is thought to be between 4:1 and 1:4. (These ratios are based on the diets of the longest lived populations at the time of the studies that investigated omega-3s and -6s)
In the UK our diet averages around 14:1 (on the pro-inflammatory side).
Excessive inflammation is associated with insulin resistance, which in turn is a major contributor to the chronic diseases that kill most people today.
Omega-6 is pro-inflammatory and omega-3 (specifically the EPA sub-type) is anti-inflammatory.
See my blog post Understanding Fats for a more comprehensive look at fats in general.
Prefer: extra virgin olive oil, olive oil, coconut oil
Maybe use: rapeseed (“canola” or “vegetable”) oil
Details: Rapeseed oil (“canola” in US; in UK usually just “vegetable oil”) may be acceptable for frying with due to its reported relatively high heat resistance, as compared to other seed oils. It usually still has an unfavourable omega-6-to-3 ratio though, and the polyunsaturated fatty acid component of it will be susceptible to heat damage when frying, which makes me question the resources that show rapeseed oil to have higher heat resistance than, say, coconut oil. I’ll be looking into this more.