Nutritional Requirements

The chemical substances that are required for the production of energy, growth, and body building are called Nutrients. The nutrients we require are Carbohydrates, Proteins, Lipids, Vitamins and Minerals. Some of them are required in large quantities and are therefore called Macro nutrients. For example, Carbohydrates and some minerals like sodium are required in large amounts. Some of the nutrients are required in small amounts often in micrograms. These are called micro nutrients. Vitamins and minerals like Iron, Molybdenum are some of the examples for micro nutrients. The procurement of nutrients is called Nutrition.
 Carbohydrates are a group of compounds that contain Carbon, Hydrogen and Oxygen. Carbohydrates are of two types Complex carbohydrates are broken down to simple sugars by hydrolysis in the digestive system and the simple sugars are absorbed. Sugars like Lactose and Sucrose are hydrolyzed by Lactase and Sucrose in the digestive system. Starch is converted into glucose in the presence of Amylase Cellulose is present in plant cells. We can’t digest cellulose. Therefore cellulose has no nutritive value for us but it adds weight to the food and helps in slow and smooth movement of food in the digestive system.

Glucose is formed from the hydrolysis of the complex carbohydrates is used by the body for the production of energy. One gram of glucose gives 4 kilo calories of energy. Excess of Glucose is converted to either glycogen or fats and stored in the body.

Proteins are made up of Carbon, Hydrogen, Oxygen and Nitrogen. Some proteins may have sulphur in Small amounts. Proteins are made up of small units called amino acids. In the digestive system the proteins breaks down into amino acids by a proteolytic enzymes and are thus absorbed from the intestine. There are 24 different amino acids in nature and of these only 20 amino acids are present in most of the proteins.

Amino acids are 2 types
1. Essential amino acids: These amino acids can not be synthesized by our body but we get only through food. These amino acids are essential for the normal growth and development.
Ex: Isoleucine, Leucine, Lysine, Methionine, Phenylamine, Threonine, Tryptophan, Valine and Histidine

2. Non- Essential amino acids: These amino acids are synthesized by our body. Proteins are of 2 types

1. Biologically Complete Proteins: In this type proteins from meat, milk and eggs are rich source for amino acids.

2. Biologically incomplete proteins: In this type, proteins from plant sources (Vegetables, Grains, Fruits etc) have lesser amounts of essential amino acids.

Fats: Fats are made up of fatty acids and glycerol. Both fatty acids and glycerol contain Carbon, Hydrogen and Oxygen. Fats are solids at 20°C. If, they are liquids at this temperature then they are called oils. Fats are digested in the digestive system by Hydrolysis to fatty acids and glycerol.

The fatty acids are of 2 types:
1) Saturated fatty acids:
These are synthesized in our body.
2) Unsaturated fatty acids: Our body can not synthesize some of the unsaturated fatty acids and it is essential that they are present in the diet we eat.
Ex: Linoleic acid

Cholesterol: It is also a type of fat present in oils and fats.
Ex: Eggs, Butter, Ghee, Meat, Oils etc.

Excess of cholesterol and saturated fatty acids are deposited in the arteries and interfere with the blood flow. This may lead to heart attacks. One gram of fat gives 9.45 kilo calories of energy; unsaturated fatty acids are required for growth and development.

These are required for growth, repair regulation of osmotic pressure and other vital processes. Minerals present in the body are classified into 2 types.

1) Major elements: Sodium, Potassium, Calcium, Magnesium, Chloride and Phosphorus

2) Trace Elements: Manganese, Molybdenum, Selenium, Zinc, Copper and Fluorine. Sodium and Potassium ions are required for maintaining the osmotic pressure in the body and for the activity of nervous system.

Calcium is required for the formation of bones, teeth, coagulation of blood, muscle contraction, activity of the nervous system and other vital activities. It is available in milk, milk products, green leafy vegetables etc. We require about 400-500 mg of calcium per day.

Iron helps to carry Oxygen from lungs to the tissues. About 60-70% of Iron in the body is present in the blood. Iron is available in green leafy vegetables, liver, meat, fish etc. Deficiency of Iron causes Anemia.

Iodine is required for the production of thyroid hormone. Iodine deficiency results in goiter. Iodine is added to common salt to prevent goiter in the population. Fluorine is required for the proper formation of bones and enamel on the teeth. Excess of Fluorine intake causes Fluorosis.

Water is the most essential constituent of life. About 90% of water is present in Protoplasm. It is a universal solvent and is a medium for a number of metabolic activities. It helps in regulation of body temperature, the transport of substances from one part of the body to the other part digested food, Hormones, excretory wastes etc.

Balanced Diet:
Food having all the nutrients in quantities required for the body is called balanced diet. A balanced diet has sufficient amounts of Carbohydrates, Proteins, Fats, Vitamins and Minerals. The amount of nutrients required for the body may be different in males and females, children and adults in disease conditions and in different states of physical and mental activities. The Indian Council of Medical Research (ICMR) has been carrying out studies on the requirements of balanced diet for the different age groups in India.

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