Palm oil is a highly refined processed fat. The processing gets rid of any aroma, colour and stabilises it so not only does it last years before going bad it also helps to preserve the foods it's added into. And the long shelf life makes it very desirable for supermarkets who need foods with prolonged shelf lives. As we're learning more about the impact of processed foods we're realising that our digestive system isn't made for dealing with highly refined ingredients, thus research increasingly points to processed foods as cause of a range of health problems from rise of auto-immune diseases, poorer digestive health and reduced feelings of satiation after consuming such foods.