Olive oil is a healthy substitute for butter. One tbsp. of olive oil has 120 calories and 14 g of total fat, including 12 g of unsaturated fat. Olive oil contains no trans fats or cholesterol. Salted butter has 102 calories per tbsp. and 11.5 g of total fat, of which 7 g are saturated. Butter also contains 31 mg of cholesterol. Excess monounsaturated fats, a low saturated-fat content and an absence of cholesterol make olive oil a better alternative than butter for the heart.