Discovery of Nutrients

Studies carried out by many scientists have shown that foods contain several chemical constituents, which are known as nutrients. These include 

(i) proteins

(ii) carbohydrates 

(iii) fats

(iv) minerals and 

(v) vitamins

The importance of these nutrients is briefly discussed below:

i) Proteins

Proteins are required for growth in children and maintenance of body weight in adults. Proteins also provide energy to a small extent. Proteins constitute about 20 per cent of the body weight. Body proteins are derived from the dietary proteins.

The body losses continuously some quantity of proteins and this loss has to be made up by dietary proteins. Proteins are made up of simpler chemical substances known as amino acids. The amino acid contents of proteins have been found to differ from one protein to another. The nutritional value of proteins depends on their amino acid contents. As a result of studies carried out by several scientists, a large amount of information is available on the nutritive value of dietary proteins and the protein requirements of human beings.

Nutrients present in foods

ii) Carbohydrates

Carbohydrates are the main sources of energy for doing work. The carbohydrates commonlv occurring in foods are starch. cane sugar. glucose. fructose and milk sugar (lactose). About 50-70 per cent of energy value (calorie value) in the average diet is provided by carbohydrates. They are the cheapest source of energy in the body. Glucose derived from the digestion of carbohydrates is used as a main source of energy in the body. Hence, the diets should contain adequate amounts of carbohydrates to meet a greater part of the energy needs.

iii) Fats

Oils and fats serve mainly as the source of energy and they contain some essential nutrients like essential fatty acids and fat-soluble vitamins. Fat is essential for maintaining good health, as absence of fat leads to the development of a deficiency diseases affecting the skin known as phrenoderma.

iv) Minerals

The body contains about 24 minerals, all of which are derived from the diet. The important minerals are calcium, phosphorus, potassium, sodium, chloride, magnesium, iron, copper, iodine, cobalt, fluorine and zinc.

v) Vitamins

Studies carried out by several pioneers have shown that foods contain certain essential chemical substances in small amounts which are now called vitamins. About 14 different vitamins have so far been discovered. All of them are essential for normal functioning of the human body. Inadequate intake of vitamins will lead to the development of deficiency diseases. Vitamins have been grouped under two heads (i) fat-soluble vitamins such as vitamins A, D, E and K and (ii) water-soluble vitamins, e.g., vitamin B,, riboflavin, vitamin B,, niacin, pantothenic acid, folic acid, biotin, vitamin C and vitamin P. A large amount of information is available on the functions of vitarnins, vitamin content of foods

and vitamin requirements.