The link between dietary fat and health was established in comparative studies that were made of the effects of different national and regional diets on disease incidence: those societies that consume a lot of cholesterol and saturated fats, (such as Britain, parts of Scandinavia and the USA) show a high incidence of heart disease, while those with low levels of saturated fats in the diet and high levels of mono and polyunsaturated fats (Southern Italy, Greece and other countries that produce and consume olive oil) have some of the lowest incidence in the world, as do certain regions with a diet rich in fish oils.