Nutrition

Nutrition, Food, and Diet:

  • Nutrition means the supply of essential organic and inorganic chemical compounds (proteins, vitamins, salts, etc.) to the body.
    • All such chemical compounds are called nutrients.
  • Food is any substance that we eat or drink, and which contains nutrients.
    • Examples: Milk, bread, egg, fish, and apple.
  • Diet: The combination of food items that we eat in our meals.
    • A balanced diet is one which includes food items that supply all the necessary nutrients.
    • [Meal is the food taken at one time to satisfy the appetite.]
    • [Appetite means the desire to eat and hunger is the uneasy sensation due to lack of food.]

Need for Nutrition:

  • All living organisms require food. It is needed for six main purposes:
    • Growth: Building up new protoplasm or cells for growth.
    • Repair: Providing material for the repair of worn-out or injured cells.
    • Energy: Providing energy needed by the body to carry out various life functions.
    • Maintenance of chemical composition of cells.
    • Provision of raw materials for the manufacture of various secretions such as enzymes, hormones, sweat, milk, etc.
    • Protection from disease and infection.

Classes of Nutrients:

  • There are six classes of food substances called nutrients.
  • These are carbohydrates, fats, proteins, mineral salts, vitamins, and water.

Carbohydrates:

  • They are the compounds of carbon, hydrogen, and oxygen, with hydrogen and oxygen always in the ratio of 2:1.
    • They are oxidized in the cells to release energy.
  • Carbohydrates include sugars, starch, cellulose, etc.
Sugar:
  • Sugars are soluble in cold water and taste like sweets.
  • Broadly, the sugars in our foods are of two major categories:
  • Monosaccharides or single (simple) sugars have a general chemical formula of C6H12O6.
    • These need no digestion and are straightaway absorbed into the body.
    • Three types of such simple sugars are:
    • Glucose, popularly known as grape sugar, is the most common and simplest sugar found in organisms.
      • (When we say blood sugar, it means the glucose level in the blood).
    • Fructose is common in plants and is popularly called fruit sugar.
    • Cialactose is another simple sugar found in milk.
  • Disaccharides or double sugars have a general chemical formula of C12H22O11.
    • These are also three and require digestion.
    • Sucrose is our commercial sugar.
      • It is commonly obtained from sugarcane in our country.
      • Another source of sucrose is sugar beet.
      • Sucrose is a double—sugar made up of two simple sugars, glucose and fructose.
      • Maltose or malt sugar is made up of two glucose molecules.
      • Lactose or milk sugar is made up of glucose and galactose.
Starch:
  • Starch is an insoluble carbohydrate. It is in this form that plants commonly store carbohydrates.
  • Potatoes, grains (rice, maize, wheat, and barley), and bread are chief sources of starch.
  • Two other insoluble polysaccharide carbohydrates are:
  • Cellulose:
    • It is found in the cell walls of plants.
    • It is unused in our body but it contributes to providing roughage for the proper functioning of the gut.
  • Roughage:
    • It is the form in which carbohydrates are stored in animals (mainly in the liver and some also in muscles).

Fats:

  • They are also composed of carbon, hydrogen, and oxygen.
    • The oxygen content in these nutrients is much less.
  • One mole of fat releases 9.45 Kcal of energy.
    • Common foods rich in fats are butter,  cream, vegetable oils, fats of meat, and fish liver oils.
    • Fats and oils are made up of fatty acids and glycerol.
Functions of Fat:
  • Fat produces energy in the body like carbohydrates.
  • It is an important storage form of food.
  • It serves as a solvent for fat-soluble vitamins
  • Fat under the skin protects the body against a rapid loss of heat (insulation)

Proteins:

  • They are large chemical molecules.
  • They contain carbon, hydrogen, oxygen, and nitrogen.
  • Nitrogen is the most essential element in proteins.
  • Some proteins may also contain sulfur and phosphorus.
  • Amino acids are the simple, smaller units of

  proteins.

  • Proteins provide chemical material for the growth and repair of body cells and tissues.
  • In the time of emergency, they may also be oxidized to release energy.
  • Foods rich in proteins include lean meat, fat-free muscles, fish, eggs, milk, cheese, nuts, beans, and peas. etc.
  • A deficiency of proteins leads to weakness but its severe deficiency causes the two diseases.
Kwashiorkor:
  • It is a severe protein deficiency disease usually affecting young children.
  • This disease is caused when mothers stop breastfeeding their babies at an early age,  and the child is given a diet rich in proteins.
  • Mother’s milk is rich in protein, and after weaning,  the child is given a diet mainly consisting of carbohydrates and poor in proteins.
  • The suffering child may die before the age of five years.
  • Symptoms:
    • Underweight.
    • Belly protruding out.
    • Skin getting dark and scaly.
    • Stunted growth.
    • Loss of appetite.
    • Repeated diarrhea.
    • Enlarged liver and anemia.
    • Oedema (swelling) of the feet and the face (accumulation of water in the tissues of the feet and the face).
  • Prevention:
    • The child suffering from kwashiorkor should be given a protein-rich diet like pulses, milk, egg, fish, and meat.
    • A mixed diet of wheat, gram, peanuts, soybean, and jaggery is also useful.
Marasmus:
  • Marasmus usually affects infants below the age of one year and is due to the deficiency of carbohydrates, fats, and proteins in the diet.
  • This disease is caused due to the sudden stoppage of breastfeeding, followed by a diet poor in energy-giving foods like carbohydrates, fats, and proteins.
  • Symptoms:
    • Less body weight.
    • Degenerations result in a very weak body as if formed of muscles, skin, and bones only.
    • Skin becomes loosely folded.
    • Thin face, thinning of limbs.
    • Retarded physical and mental growth.
    • Ribs appear prominent.
  • Treatment:
    • The child suffering from marasmus should be given a diet rich in proteins and carbohydrates.

Mineral Salts:

  • They are needed in the diet in small quantities.
  • Table salt contains mainly sodium chloride.
  • Many other mineral elements are obtained from various foodstuffs such as green vegetables and fruit.
  • Some important mineral elements and their nutritional values are as follows:
    • Calcium and phosphorus for strengthening bones and teeth.
    • Calcium is also required in process of clotting blood.
    • Phosphorus is required in various chemical processes, such as in the production of chemical energy (ATP) during cell respiration.
    • Rich sources: milk, meat, eggs, fish, pulses, vegetables, etc.
    • Iron for forming hemoglobin; its deficiency leads to anemia.
    • Source: green leafy vegetables. liver, etc.
    • Iodine is for the proper working of the thyroid; its deficiency leads to goiter.
    • Sources: vegetables, mineral water, etc.
    • Potassium and sodium for cell permeability, especially in nerve cells.
    • Sources: most foods and table salt.

Vitamins:

  • They are chemical substances needed in minute amounts, which help maintain a healthy body.
  • Most vitamins act as catalysts or enzymes in essential chemical changes in the body but each vitamin has also some special function in our body.
  • Vitamins are contained in foods naturally but a couple of them are also synthesized in our bodies.
  • Some vitamins (A, D, E, and K) are fat-soluble and can be stored in the body, for a longer period of time but some others (B complex containing several vitamins named B1, B2, etc. and C) are water-soluble and cannot be stored for a longer period of time.
  • The absence or shortage of vitamins in diet over a continued period causes deficiency diseases. In a low concentration, vitamins have a catalytic and regulatory function in cell metabolism.
  • Excess of vitamins may also be harmful. 
  • Excess water-soluble vitamins are easily excreted out.

Water:

  • It is indispensable.
  • About 2/3 of our body weight is water.
  • It serves several functions:
    • It acts as a solvent in the body for thousands of substances both organic and inorganic.
    • It is used to produce digestive juices.
    • It helps in the transportation of digested foods and oxygen throughout the body
    • It is used in the excretion of soluble wastes.
    • It is involved in the maintenance of body temperature.
  • Loss and replacement:
    • Water is regularly lost from the body through sweat, urine, and water vapor in the breath.
    • Therefore,  it must be constantly replaced.
    • The liquids we drink and our foods, such as fruit and vegetables, which we eat supply water to the body still we should drink sufficient water every day.