Nutrients-Foods-Balanced Diet

Nutrients, food and balanced diet

For the proper functioning of human body, correct proportion and quantity of nutrients or diet is required which is termed as Balanced diet. Nutrients are the chemicals present in the food such as carbohydrate, protein, lipid, vitamin, inorganic minerals salts and water.

Composition of food

1. Carbohydrates

Carbohydrates are the primary source of energy for the body. Major proportion of food contains carbohydrates. Carbohydrates includes sugar and starch.

Sources: plant sources; cereals (wheat, maize, rice), potatoes, sugarcane, fruits,

Animal sources; meat and liver (stored glycogen), milk, Honey

Daily requirement: 500gm per day for a health adult.

Functions of carbohydrate:

  1. Energy source: glucose is the immediate source of energy while glycogen is the storage source of energy in animal. Complete oxidation of 1 gram carbohydrates give 4.2 kcal of energy.
  2. Regulation of blood glucose level
  3. Cell to cell recognition: glycoprotein and glycolipid are the cell surface receptor, which helps in cell to cell recognition
  4. Antiketogenic role: carbohydrate prevent incomplete oxidation of fats and formation of ketonic bodies
  5. Shock absorber: Hyaluronic acid present in vitrous humor of eye and synovial fluids in joints helps in shock absorption
  6. Dietary fibre: cellulose present in cell wall of plant cell is important for fibre in diet.
  7. Carbohydrates prevent the use of proteins for energy


2. Proteins

Proteins are complex organic compounds. They are mainly used for growth and repair. They can also be used as source of energy if diet is deficient in carbohydrates and fats. They are the polymer of aminoacids.

Essential aminoacids: they cannot be synthesized in the body, so they should be essentially present in diet. Examples: leucine, isoleucine, lysine, phenylalanine, tryptophan, valine, methionine and threonine. Arginine and histidine are semi essential aminoacids. Infants lacks while adult can partly synthesize.

Non-essential amonoacids: those aminoacids which are synthesize by the body, so are not essential to be included in diet. Examples:  alanine, serine, glycine, glutamine, tyrosine, aspartic acids, cysteine, proline, glutamic acid and asparagine.

 Sources: plant sources; soyabean, pulses, cashew, fruits etc

Animal sources; meat, egg, milk, fish, cheese etc

Daily requirement: adult: 0.8 gram per Kg weight

Functions of protein:

  1. Cell to cell recognition: glycoprotein and lipoprotein are the component of cell membrane.
  2. Movement: actin and myosin protein helps in muscle contraction during movement.
  3. Blood clotting: thrombin and fibrinogen helps in blood clotting
  4. Defense: Antibodies and Immunoglobin are proteins which provide immunity.
  5. Transport: some protein acts as carrier molecules and helps in active transport.
  6. Hormones and enzymes: Hormones and enzymes are proteins, which catalyse the biological activities of the body.
  7. Energy source: in deficiency of carbohydrates and fats, proteins serve as fuel for the body. 1 gm of protein produces 5.6Kcal energy.
  8. Repairing: they are essential for repairing of dead and wounded tissue
  9. Growth : proteins made the structural component and take part in growth and development of the body


3. Lipids

Lipids includes fats and oil. Fats are solid at room temperature whereas oils are liquid at room temperature.  The lipid found in food are mainly triglycerides (TGA) which is composed of glycerol and fatty acids.

Sources: animal source; animal fats, meat, milk, butter, cheese, egge, fish etc

Plant source; oil, mustard seed, ground nut, coconut, sunflower seed etc

Daily requirement: adult; 50 gm fat daily

Functions of lipid:

  • Energy source: lipids are important source of energy. 1 gm fat give 9.6 Kcal of energy.
  • Storage source of energy: triglyceride are stored as body fat (adipose tissue) and protect the internal organs from shocks.
  • Insulation: sub-cutaneous layer of fat serves as thermal insulator
  • Solvent: it serves as solvent for fat soluble vitamins (Vit. A,D E and K).
  • They made the components of cell membrane.
  • Steroids: they are the complex lipids and are the precursor of steroid hormones (testosterone, progesterone, adrenocorticotropic hormone,etc). they are also essential for synthesis of vitamin D.


4. Vitamins

Vitamins are the organic compounds required in small amount for biological functions rather than for energy. They are not synthesized by human body. They should be essentially present in diet for metabolism.  Vitamins are of two types on the basis of solubility.

  1. Fat soluble vitamins: A, D, E and K
  2. Water soluble vitamins: B and C

4.1. Vitamin A (Retinol):

  • sources; fish, egge, liver, milk, carrot (carotenoids), green leafy vegetables. Papaya, tomatoes etc

Functions :

  • Growth: it is essential for normal epithelial structure and growth.
  • Rhodopsin synthesis: Retinol is converted into retinal which form visual pigment (rhodopsin) in the rod cells of retinal. It help in dim light vision.

Deficiencies; Night blindness, Xerophthalmia, Keratomalacia, retarded growth.


4.2 Vitamin D (Calciferol):

sources; fish, meat, liver, eggs, green vegetables. Sunlight is essential for conversion of ergocalciferol into vitamin D. skin liver and kidney play role in synthesis of active Vit.D.


  • Promote calcium and phosphorous absorption from gut and regulate calcium metabolism.
  • Help in normal growth of bone and teeth.

Deficiencies: Rickettsia, osteomalacia,


4.3 Vitamin E (tocopherol):

sources; vegetable oil, sunflower oil, peanut oil, milk, butter, eggs


  • Beauty vitamin; maintain growth of germinal epithelium of gonads.
  • Helps in normal reproductive functioning. Also known as anti-sterility vitamin.

Deficiencies: muscular dystrophy, sterility, macrocytic anaemia


 4.4 Vitamin K (Phylloquinone):

sources; spinach, cabbage, sprouts, tomatoes, sunflower, liver, meat


  • Prothrombin synthesis: it is necessary for synthesis of blood clotting factors VII, IX and X. It helps in blood clotting. Also known as anti haemorrhagic vitamin.

Deficiencies: hypoprothrombinemia, haemorrhage, haemolytic anaemia


 4.5 Vitamin B:

sources; wheat, yeast extract, meat, liver, kidney, egg, cheese, milk, green vegetable

B1 (thiamin):

  • it is essential for normal growth.
  • It acts as coenzyme (Thiamine pyrophosphate (TPP)): for carbohydrate metabolism during Kreb’s cycle.
  • Deficeienies: Beriberi, heart failure, paralysis, Oedema, ketosis


B2 (Riboflavin):

  • act as coenzyme for cellular oxidation and reduction reaction
  • Deficiencies: tongue sore, cheilosis, keratitis, dermatitis.


B3 (Niacin):

  • Coenzyme NAD+ and NADP+ are involved in various metabolic reactions
  • Deficiencies: Pellagra


B5 (Pantothenic acid):

  • It form coenzyme A, which is involved in carbohydrate, protein and lipid metabolism
  • Deficiencies: dermatitis, burning feet syndrome, accromotrichia


B6 (Pyridoxine):

  • act as coenzyme for aminoacids and fatty acid metabolism. It is also involved in erythropiosis
  • Defeciencies: Dermatitis, muscle cramp, paralysis


B7 (Biotin):

  • act as coenzyme for carboxylation reaction.
  • Deficiencies: Acne, muscle pain, dermatitis.


B9 (Folic acid):

  • act as coenzyme for aminoacid synthesis, which inturn help in RBC maturation.
  • Deficiencies: slow maturation of RBC, anaemia,


B12 (Cynocobalamin):

  • help in nucleoprotein synthesis and maturation of RBCs
  • Deficiencies: pernicious anaemia,


4.6 Vitamin C:

sources; citrus, grapes, pineapple, chilly, green vegetables

Functions: essential for collagen fibre synthesis, and protein metabolism

Deficiencies: Scurvy, bleeding of gum, poor wound healing


5. Minerals:

minerals are essential inorganic compounds which are needed in small amount. They regulate metabolic activities. On the basis of amount required, they are classified into two groups

Macro-elements (more than 1gram): Ca, Mg, K, Na, Cl, S and P

Micro-elements (less than 1 gram): Cu, Zn, Co, Cr, Se, Fe, Mn, I, F, etc

 Sources: milk, cereals, egg, vegetables. Seafoods, cheese, water, meat, salt

Functions of mineral:

  • They maintain the homeostasis and osmoregulation.
  • They help in nerve impulse conduction
  • They maintain proper PH and osmotic pressure of the body.
  • They are necessary for blood clotting
  • They are necessary for erythropoiesis

Deficiencies: Metabolic disorders


6. Water:

It is the important inorganic compound. Human body comprises of 60-70% water by weight. Most of the metabolic activities in the body took place in the presence of water.