Margarine. Knife scoops margarine from a plastic tub. Margarine is a butter-substitute that does not contain dairy fat, but is usually made from vegetable oils and skimmed milk. It may also contain vitamin A and D supplements. Margarine is used as an ingredient in food recipes and in cooking. Margarine that is high in polyunsaturated fat is a healthy alternative to butters containing saturated fat. Saturated fat affects blood cholesterol and contributes to heart disease.