Lipids consist of a broad group of compounds that are generally soluble in organic solvents but only sparingly soluble in water. They are major components of adiposa tissue and together with proteins and carbohydrates, the constitutes the principal stuctural components of all living cells.

Dietary lipids play an important role in nutritions. They supply food calories and essential fatty acids, act as vitamin carrier, and increase the palatability of food, but for decades, lipids have been at the center of controversy with respect to toxicity and desease.

Fats and lipids serve as a concentrated sorce of energy. As compared with proteins and carbohydrates, they supply twice as many food calories per gram (9 versus 4 kilocalories/gram). The essential fatty acids (EFA) linoleic and arachidonic, as well as fat soluable vitamin A, D, E and K, are obtained from the lipid fractions of the diet. Linoleic acid is converted in the body to arachidonic, which is the precursor of a group of hormones known as prostaglandins.

During the last four decades researchers have been preoccupied with the theory that dietary fats are the important cause of coronary heart desease or cardiovascular desease. Cholesterol and saturated fats are presumed to raise the level of blood serum cholesterol, which in return leads to the deposition of the atherosclerotic plaques on the arterial walls.