Butter is for bread, oil is for cooking.
I do not use butter for cooking. Except for some desserts.
Ideally butter should not be heated and excessive butter consumption can lead to health problems – mostly cardiovascular as it is high in saturated fat. However, it is delicious when melting slowly on a warm slice of a fresh wholegrain bread (yum!) I replaced it with plant oil for cooking and kept it for our gourmet weekend breakfasts.
I am not a big fan of margarine as an alternative. It is an industrial product made of various plant oils with added emulsifiers and preservatives. Most margarines contain palm oil which is not the healthiest one because it is high in saturated fat. Furthermore, it is disastrous for the planet because its production leads to massive deforestation.
The star of my kitchen is olive oil.
A pillar of the Mediterranean diet, it is rich in monounsaturated fatty acids (Omega 9) and polyphenols which play an important role in preventing cardiovascular diseases. Extra virgin olive oil (cold-pressed ones retain most of the nutritional quality) shouldn’t be subjected to high temperatures. It should not be heated above 190°C. Virgin olive oil (without the “extra”) is slightly heated during the extraction process so even though it is less nutritious it can be cooked at up to 216°C.
The mix of extra virgin olive and rapeseed oil is nutritionally very interesting. Rapeseed brings in the highly beneficial Omega 3 (polyunsaturated fatty acids), balances well the fruity taste of olive oil and becomes more heat resistant.
I also use delicately flavoured coconut oil. Nutritionists have opposing views on it because it is rich in saturated fatty acids (like butter or palm oil). But it is perfect for high-heat cooking and adds flavour to some Asian inspired dishes and desserts.
Walnut and sesame oils have their place as well in my kitchen because of their nutritive quality and the rich flavour they add to my salad or cold-dish dressings. They are however very thermo sensitive.