Oils & fats. Assortment of dietary oils and fats. In the front row are butter, lard and soya margarine. The back row has oil made from (from left to right): corn (maize), sunflowers, groundnuts (peanuts) and olives. Oils and fats are a good source of energy and are an essential part of the diet, and they often have important vitamins dissolved in them. Unsaturated oils extracted from plants are healthy because they lower the level of cholesterol in the blood. Saturated fats from animals, such as in lard and butter, raise blood cholesterol levels. High levels of blood cholesterol can lead to high blood pressure, heart attacks and strokes.