Some fascinating new research has thrown up a few issues with our choices of oils and fats for cooking.
It seems that subjecting certain fats to high temperatures can release aldehydes because you are changing the structure of the fats.
Have a look at this BBC news article to help you make an informed choice - and maybe stop you worrying about using animal fats!
Consuming or inhaling aldehydes, even in small amounts, has been linked to increased risk of heart disease and cancer.
Prof Grootveld suggests that when it comes to cooking, frying in saturate-rich animal fats or butter may be preferable to frying in sunflower or corn oil.
Lard, despite its unhealthy reputation, is actually rich in monounsaturated fats.
"Sunflower and corn oil are fine," Prof Grootveld says, "as long as you don't subject them to heat, such as frying or cooking.
He recommends olive oil for frying or cooking. "Firstly because lower levels of these toxic compounds are generated, and secondly the compounds that are formed are actually less threatening to the human body."
To try and reduce aldehyde production, choose an oil or fat high in monounsaturated or saturated lipids (preferably greater than 60% for one or the other, and more than 80% for the two combined), and low in polyunsaturates (less than 20%).
That's why olive oil is a good compromise - because it is about 76% monounsaturates, 14% saturates and only 10% polyunsaturates.
Obviously, when you are cooking, just try to minimise the amount of oil you use and eat.
Lastly, Prof Grootveld suggests you be careful with how you store your oil. Fats are susceptible to oxidation when they are exposed to light, heat and oxygen so try and keep your oils tightly sealed in a cool, dry cupboard.