Dietary fats and nutrition

Abstract

Dietary fats of animal or vegetable origin are classified as Visible’ (adipose tissue, milk fat, seed oils) or ‘invisible’ (derived from animal or vegetable membranes). They are mainly triacylglycerols along with minor amounts of phospholipids, glycolipids, sterol esters, and vitamins. Fats are the richest source of energy on a weight basis and excess of fat beyond daily energy requirement is laid down as reserve depot fat, usually after some structural modification. Storage fat is to be found in adipose tissue, in milk fat, in the flesh of fatty fish, and in seed lipids. Fats in the adipose tissue are mainly triacylglycerols of saturated and unsaturated acids. The composition of this fat is not very critical and tends to reflect dietary intake (exogenous fat). Fat made in vivo from protein or carbohydrate is described as endogenous fat. The lipid composition of milk fat is more critical and is generally rich in essential fatty acids required by the neonate. It is, however, influenced by maternal diet. When storage fat is mobilized and metabolized it is oxidized to carbon dioxide and water with liberation of energy (section 7.4.2).