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| Classification of Food - Continued |
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| Fats are also known as lipids. They are long molecules of fatty acids and an alcohol called glycerol. Fats contain the same elements as carbohydrates i.e., carbon, hydrogen and oxygen, but the oxygen content is lower. |
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| The main function of fats is to provide energy. In fact they provide twice the amount of energy as that provided by the same amount of carbohydrate. One gm of fat gives about 37 kilojoules of energy which is more than double that of carbohydrates. Fats are involved in the formation of the structural materials of cells and tissues such as cell membrane and cell organelles. They are solvents for certain vitamins like vitamin A, D, E and K. Fats deposited around the internal organs like kidneys, livers, ovaries etc. act as a protective shock absorbing cushion. Fats can also be stored in the body for subsequent use when we eat food which has more energy than we can utilize while doing work, then this excess energy gets stored under our skin as subcutaneous fat. This fat insulates the body against cold and also acts as reserve source of energy. |
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| The fats present in our food cannot be absorbed by our body as such because they are complex organic molecules which are insoluble in water. During the process of digestion, by the action of an enzyme called lipase, secreted by the pancreas, fats are broken down into simpler substances called fatty acids which get synthesized further so that they can finally be assimilated into the blood, in the intestine. On oxidation, they produce energy. One gram of fat gives 9.3k cal of energy. |
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| Food substances that are rich in fats are butter, Ghee, Cheese, Milk, Egg yolk, Meat, Nuts. Groundnuts and oil. (Oil extracted from coconut, sunflower, mustard seed, sesame seed) |
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| If fats do not solidify at 20oC they are called oils. There are two types of fatty acids. |
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| Classification of fatty acids |
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| A healthy diet should contain less of saturated fats like butter and ghee because these fats easily change to cholestrol. Cholestrol is known to cause diseases like arteriosclerosis (thickening of artery walls), high blood pressure and heart disorders. |
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| Test for the presence of fats |
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| Take some groundnut seeds and crush them with a heavy object on a clean white sheet of paper. Keep the crushed ground nut on the paper for a few minutes. Now remove the ground nut pieces and hold the paper against light. Appearance of translucent greasy spots on the sheet of paper show the presence of fat (oil) in ground nut. |
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| Vitamins are nutrients which are essential to life. They are organic compounds needed in small quantities, necessary for the healthy growth and maintenance of the body. Vitamins are found in all kinds of foods but, vegetables and fruits are particularly rich in vitamins. |
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| Based on solubility, vitamins are grouped into two classes |
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| Classification of vitamins based on their solubility |
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| The B-complex group of vitamins consists of vitamin B1, B2, B4, B6, B12 and folic acid. Table5 gives the daily requirement of vitamins for children between 13-15 years, their sources and their functions. |
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| Table 5. Daily requirement of vitamins for 13-15 year-old boys and girls, their sources, and their functions |
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IU=International Units, mg=miligram (1/1000 gm),  |
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| Since vitamins are easily destroyed on storage or prolonged boiling, for best vitamin value, food should be eaten in its freshest possible state. Water used for cooking vegetables should not be discarded as they contain water soluble vitamins. The stock should be used in soups or for preparing the gravy. Patients under the treatment of antibiotics should be simultaneously replenished with B-complex capsules as these drugs have a tendency to destroy the natural intestinal flora (bacteria) that synthesize these vitamins. |
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| Carbohydrates, fats and proteins are all carbon compounds or organic compounds. Minerals are inorganic substances, several of which are metals and their salts. Minerals do not supply us with energy but they are required to build bones and teeth, formation of red blood cells, clotting of blood, functioning of muscles, nerves and thyroid gland etc. Some of the important minerals required by our body are iron, iodine, calcium, copper, chlorine, phosphorus, potassium, sodium, sulphur, flourine, magnesium and zinc. |
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| Table 6. Daily requirement of important minerals and their functions |
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