A balanced diet is an optimal combination of all the basis classes of foods – carbohydrates, proteins, fats, vitamins, minerals, fibers and water – taken in sufficient quantities and in the correct proportion.
It has the following functions: a) provide sufficient energy to maintain the basic metabolic rate (BMR) – heart beat, circulation of blood, maintenance of body temperature, breathing, etc., and to sustain additional activities of the person b) enables to growth processes and assimilation to take place by providing the necessary basic materials c) sustains the health, by providing protection against diseases and raw materials for the production of secretions such as hormones and enzymes.
The amount of energy to be provided by a balanced diet for any person will depend on several factors: age, sex, body size, lifestyle, occupation, and the climate of the area he is in.
Energy Value of Food
The energy value of food and the energy requirements in human can be calculated in terms of heat energy. In the past, heat energy has been measured in calories which are defined as:
1 calorie is the heat required to raise the temperature of 1 g of water by 1° C.
With the introduction of the S.I units, the unit of heat used now is the joule, which is defined in terms of the work done. Mechanical work can be converted into an equivalent amount of heat, and therefore both can be measured in the same units. The relationships between these two units are as follows:
1 calorie (cal) = 4.2 joules (J)
1 kilocalorie (kcal) = 4200 joules
= 4.2 kilojoules (kJ)
The energy value of food is defined as the total amount of heat released when one gram of food is oxidized completely. It is measured in the units’ joules per gram (Jg-1). The following diagram shows the apparatus that can be used to measure to heat produced by the burning of food.
VitaminsVitamins are complex organic compounds. They are required in very small quantities to maintain our health. They play an important role as co-enzymes in various enzymatic reactions and for building and maintaining body tissues in healthy conditions. Various organisms do not need similar enzymes, e.g. humans need vitamin C but other do not. Plants are able to synthesis the vitamins required. Animals are unable to do so and have to obtain them from plants