Human Nutrition 3(3+0)

Lesson 1 : Historical Development and the Relation of Nutrition to Health, Growth and Human Welfare

Discovery of Nutrients

Foods contain several chemical constituents which are known as nutrients. These include proteins, carbohydrates, fats, minerals and vitamins. The importance of these nutrients is briefly discussed below.

1. 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 percent of the body weight. Body proteins are derived from the dietary proteins. The body loses 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 content of proteins has been found to differ from one protein to another. The nutritional value of a protein depends on its amino acid contents.


2. Carbohydrates: Carbohydrates are the main sources of energy for doing work. The carbohydrates commonly occurring in foods are starch, cane sugar(sucrose), glucose, fruit sugar (fructose) and milk sugar (lactose). About 50-70 percent of energy value (Calorie value) in the average diet is provided by carbohydrates. They are the cheapest source of energy. Hence, the diet should contain adequate amounts of carbohydrates to meet a greater part of the energy needs.


3. Fats: Oils and fats mainly serve as sources of energy. They contain some essential nutrients like essential fatty acids. Fat is essential for maintaining good health. Absence of fat leads to a deficiency disease affecting the skin known as phrynoderma.


4. 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. Minerals are essential for various body functions, Such as:
1. Calcium and phosphorus for formation of bones and teeth.
2. Sodium, potassium and chloride for maintaining water balance in the body.
3. Iron and copper for formation of hemoglobin,
4. Iodine for the normal functioning of thyroid gland.


5. Vitamins: Foods contain certain essential chemical substances in very small amounts were called as vitamins. About 14 different vitamins discovered. All of them are essential for normal functioning of the human body. Inadequate intake of vitamins leads to the development of deficiency diseases. Vitamins have been grouped under two heads
1. fat-soluble vitamins such as vitamins A, D,E, and K
2. water-soluble vitamins, e.g. thiamine (vitamin B1), riboflavin(vitamin B2), niacin, pyridoxine (vitamin B6), vitamin B12 pantothenic acid, folic acid, biotin, vitamin C.