Agribusiness managementAgriculture

Constituents of food and its functions

Constituents of Food and Functions

Humans are omnivorous in nature and draw nutrition from food which could be from either or both plant and animal sources. Certain edible fungi such as mushrooms also serve as food. The vital nutrients that can be obtained from food are carbohydrates, proteins, fats, vitamins and minerals.


Carbohydrates, in simplest terms, are sugars and contain carbon, hydrogen and oxygen. They are the main source of energy in the human diet. Carbohydrates can be classified as monosaccharides, the simplest form which includes include glucose, galactose and fructose; disaccharides such as lactose, maltose and sucrose which consists of two units of simple sugars and the most complex polysaccharides that consist of more than two units of monosaccharides viz. starch and cellulose. Rice, maize, wheat, barley, potato, sugarcane, beetroot, banana, grapes etc. are some of the important sources of carbohydrates. Carbohydrates are broken down by the process known as oxidation and energy thus released is utilized by the body to carry out all the functions. The released energy is measured in calories.


Amino acids are the building blocks of proteins. Proteins are complex high molecular weight compounds that play a structural and functional role in all living cells. They are essential for the growth and repair of the body tissues. In terms of human nutrition, proteins are of two types depending on their source – animal protein such as milk, cheese, meat, egg etc. and vegetable protein such as pulses, soya beans, nuts and grains. Proteins are metabolized to provide energy when the body is starved and is devoid of any carbohydrate source.


This is the most concentrated source of energy. Fats are made up of carbon, hydrogen and oxygen; the oxygen content is much lesser as compared to that of carbohydrates resulting in the production of a larger amount of energy when oxidized. Fat forms energy reserves in the body and is mainly stored under the skin. Butter, ghee, milk, fish, meat, nuts and oils are the main sources of fat. One gram of fat when burnt gives nine calories of energy.


Vitamins are vital for maintaining normal growth and health. Unlike carbohydrates, proteins and fats, vitamins do not provide energy but they are essential for proper absorption of carbohydrates, proteins, fats and minerals by the body. The various types of vitamins are A, B, C, D, E and K. There is no single food that provides all the vitamins required for our body, hence a variety of foods should be taken in balance in order to obtain all these vitamins in required amounts. Deficiency of vitamins leads to various disorders.


Minerals such as iron, calcium, copper, iodine, sodium, phosphorus, zinc etc. along with vitamins are required in small quantities by our body for normal growth and proper functioning. Iron is the main component of haemoglobin that transports oxygen to tissues. Calcium is required for the formation of bones and teeth. Likewise, each of the minerals has a role in maintaining body functions.


Water constitutes 70% of our body and is required for all the biological processes in our body. It is essential for transporting food, hormones and other nutrients throughout the body. It flushes out toxins and other wastes out of the body in the form of urine and sweat. It regulates body temperature


The fiber content of our diet that helps in easy movement of food in the alimentary canal is known as roughage. It is essential for the proper functioning of the digestive system. Fruits, vegetables, corn, salads and cereals are highly fibrous foods.

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