Studies have also shown that people in Mediterranean countries who consume a lot of olive oil have less risk of heart disease (although this may be due also to other dietary factors, such as eating more vegetables). Olive oil is a mono-unsaturated fat, which means that when used for cooking, it is less susceptible to being damaged by heat and turn- ing into a harmful ' trans fat' , which is what happens to some other oils such as sunflower oil. Trans, or altered, fats can' t be used properly by the body and are more likely to accumulate.