Explain the basic Concept of Energy?
Energy in simple terms may be defined as the ability, or power, to do work. As a student of dietetics and nutrition, you already know that he physiological sources of energy are carbohydrates, protein, fats - the macronutrients present in food. Energy is released by the metabolism of food and the potential energy value of foods is expressed in terms of the kilocalorie (Kcal). A kilocalorie is defined as the amount of heat required to raise the temperature of 1 kg of water through I' Celsius (centigrade). Internationally, you may notice that the unit of energy measurement commonly used is the Joule (J). It expresses the amount of energy expended when 1 kg of a substance is moved 1 meter by a force of 1 Newton. The conversion factor for changing kilocalories to 1ciIojoules is 1 kilocalorie = 4.184 kilojoules. The amount of heat energy (kilocalorie) per grim1 that can be made available to the body by each of the energy-yielding macronutrients - carbohydrate, protein, fat - must be known to you. Yes, 1 g of carbohydrates yields 4 Kcal, 1g of fat yields 9 Kcal, and 1 g protein yields 4 Kcal. These values are known as the physiological fuel factors; Do you know how the energy in various foods is generally measured? The amount of energy available in a food is precisely determined by a laboratory technique known as calorimetry. In this process, a weighed amount of food is placed inside a metal container called a bonzb calorimeter, which is immersed in water. The food is then ignited in the presence of oxygen and burned. The increase in temperature of the surrounding water is measured and used in calculating the number of kilocalories given off by the oxidation of the food, an alternate method of measuring food energy is to use the macronutrient composition of foods in the food composition tables and by using the physiological fuel factors referred to earlier. The Indian Council of Medical Research (ICMR), India has published food value tables in a book titled 'Nutritive Value of Indian Foods'. Certainly, as a student of nutrition or dietetics, you may have referred la this book some time or other.