Cooking is complicated enough these days without throwing in instructions on which oils you should be using, but what you may not know is that many health factors could depend on it and some of the things you don’t know might surprise you.
The cooking fats and oils that you choose could determine things like longevity, susceptibility to certain diseases and overall health and wellness, and it can certainly be confusing with all of the contradicting information that is out there about fats and oils now. So, which fats and oils are a really bad idea and which ones actually are healthy?

The World of Oils is Wide Open to Us
Part of the reason that choosing the right oils is so difficult is that there are too many choices out there, like many things in our modern, world-at-your-fingertips society.
The aisles of the grocery stores are filled with just about every type of oil that you can imagine, but which ones should you be cooking with and why? More importantly, how do you know which ones to avoid and what negative impact can using those oils to cook actually have?
The answer to those questions begins with getting rid of preconceived notions that you might already have about which oils are healthiest. You may think that vegetable oils are the healthy option when you are up against lard or butter, but is that truly the case? What about other types of oil like corn oil, olive oil, goose fat, sunflower oil and rapeseed oil?
A Study in Leicester Trims the Fat
De Montfort University in Leicester experimented with many of these different types of oils, heating them up to cooking temperatures in order to find out what changed about the molecular structure of the fats and how oxidation affects the nutritional information.
What they found is that two oils that are normally thought to be healthy oils, could not be used for cooking. Sunflower oil and corn oil both have a lot of polyunsaturates and when they are heated, they give off a chemical called an aldehyde, which is dangerous even minute amounts and has been shown to increase risk of both heart disease and cancer.
Rapeseed oil (cold-pressed), olive oil, butter and goose fat all were much healthier than sunflower and corn oil. They produced a great deal fewer aldehydes and threaten health less.
What Kinds of Oils You Should be using
While most people avoid lard because it has a reputation as an unhealthy substance it is actually a great source of monounsaturated fats, or the good kind.
Researchers say that if you have a choice between lard and the oils that have a large amount of polyunsaturates, choose the lard, because it is much healthier.  Scientists participating in the research at De Montfort also recommend that you try to avoid frying anything, and when you do use the lowest amount of oil that you can.
You should also try to remove as much oil from the finished foods as you can before eating. The ideal oil for cooking is probably olive oil, because 90 percent of it is made of monounsaturated fats and saturates.
Sources:
http://www.eatingwell.com/nutrition_health/nutrition_news_information/what_is_the_healthiest_oil_to_cook_with
http://www.webmd.com/food-recipes/healthy-cooking-oils-buyers-guide
http://health.clevelandclinic.org/2014/10/heart-healthy-cooking-oils-101