Lipids at desired level are essential as:
- A source of essential fatty acids
- Most concentrated source of energy
- Reserve energy supply in body
- Carrier for fat soluble vitamins like A, D, E & K
- Synthesizer of important compounds like phospholipids, cholesterol etc.
- Cushion and insulation for body
- satiety factor (sense of satisfaction from meals)
Classification of Fat
Fat is classified as saturated, monounsaturated or polyunsaturated according to the type of fatty acids it contains. Most of animal origin and hydrogenated fat is saturated and is generally in a solid form and at room temperature. Other fat from plant sources is mostly mono or polyunsaturated and thus is in the form of liquid and at a room temperature. Sunflower, corn, cottonseed, soybean and sesame oil are sources of polyunsaturated fat. Fatty fish like mackerel, salmon & herring also contain polyunsaturated fat. Olive oil and most of the nuts contain monounsaturated fat. Recent studies indicate that the optimum ratio of saturated, monounsaturated & polyunsaturated fat should be 1:1:1. Thus inclusion of equal proportion of all three types fat is advisable.
Foods of animal origin provide cholesterol. Organ meat & egg yolk is very a rich source, whereas, shrimp, meat, poultry, whole milk, are moderately rich in cholesterol. It is important to note that, foods from vegetable origin do not contain cholesterol. Besides dietary source (exogenous source), liver synthesizes (endogenous source) around two grams of cholesterol daily.
Dietary factors restricting endogenous synthesis are:
- Restricting intake of saturated fat.
- Restriction of total energy intake.
- Higher meal frequency (6–7 meals daily)
- Restriction on intake of cholesterol rich food.
- Higher intake of soluble fiber (pectin, lignin etc).
- Plant sterols provided by vegetable oils which inhibit cholesterol absorption.
- Intake of rice bran oil, vegetables & fruits, garlic, ginger, fenugreek seeds (hypocholesterolaemic agent).