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Fat

Fat has many important functions in food. It enhances flavour and adds to the enjoyment of eating. As a nutrient it provides a concentrated source of energy, it acts as a medium for fat-soluble vitamins A, D, E and K and contains the essential fatty acids (EFAs) alpha linoleic acid (n?6) and linolenic acid (n?3). These are the only two fatty acids that the body cannot make for itself. They are important in the formation of cell membranes, particularly in nerve tissue.

The building blocks of fat are fatty acids and glycerol. A fatty acid is made up of a chain of carbon atoms with an ethyl group at one end and an acid group at the other. A saturated fatty acid has a full complement of hydrogen atoms bonded to the carbon chain, whereas if hydrogen atoms are replaced by a double bond then the fatty acid is unsaturated. A monounsaturated fatty acid has one double bond whereas polyunsaturated fatty acids have more than one.

The nature of the fat depends on the types of fatty acids which make up the molecule. All fats contain both saturated and unsaturated fatty acids and it is the proportion of each of these that determines the characteristics of the fat.

Butter is often described as a saturated fat because it contains more saturated fats than unsaturated. Vegetable oils are described as unsaturated fats because they contain more mono- or polyunsaturated fatty acids. Saturated fats are solid at room temperature whereas unsaturated fats are usually liquid at room temperature.

A high fat intake, has been associated with a raised blood cholesterol level. This is one of the risk factors for coronary heart disease. High total fat intake is also associated with overweight and obesity, which are also risk factors in heart disease, some cancers, non?insulin dependent diabetes and hypertension. It also exacerbates respiratory conditions, arthritis etc.

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