Food and nutrition.pdf

56 Nutrientsingested food or by supplying it to the blood when it is needed by thebody cells for energy.Cellulose is the main structural material of plant life, being the chiefingredient of cell walls of cotton, wood pulp, straw, com cobs, and manyother materials. Fibre includes a variety of carbohydrates and othercomponents.The chemical linkages in starch and glycogen can be split by the humanintestinal enzymes, but those of polysaccharides found in fibre are indigestible,although some fibre components can be broken down by enzymes released byintestinal bacteria to short-chain fatty acids that can be reabsorbed.ProteinsProteins are the structural components of the body forming the basisof cells, tissues and organs. They are a large group of organic compoundsconsisting of carbon, hydrogen, nitrogen and oxygen atoms. Some containsulphur and phosphorus also. When the proteins are digested they breakdown into smaller units called amino acids. Of the 20 basic amino acids12 can be manufactured by the body and the rest, called the I essentialamino acids' must be obtained from food.Proteins help to repair worn out or diseased tissues and to build newones. It is used in the formulation of hormone, enzymes, red blood cellsand antibodies. It also provides amino acids necessary for growth of fetusin pregnancy and for the production of milk proteins during lactation.Proteins are widely found in foods derived both from plant and animalsources. Plant sources include beans, peas, pulses, whole grains, nuts andoil seeds; while red meat, poultry, fish, milk, cheese, yogurt and eggs areobtained from animals. Red meat is a good source of essential amino acidsand iron and is traditionally regarded as 'first class' protein. But too muchconsumption of red meat may be harmful as it is a major source ofundesirable saturated fat. One can eat more fish or chicken without thefatty skin instead of excess red meat. Vegetarians can obtain plenty ofboth from plant sources, whole grain cereals and from low fat diaryproducts. A protein deficiency especially in infants and growing childrencan cause growth retardation, severe wasting of muscle etc.The dietary requirements of protein depend on age and physiologicalstate. A part of the dietary protein is utilised or wasted to meet the energyrequirements. So calorie intake should be adequate enough to meet theprotein need or its maximum utilisation, taking into account the abovefactor.FatsFats, oils, and waxes belong to the group of naturally occuring organic