Nutrients are organic and inorganic complexes that are found in our food. There are more than 50 different nutrients that are normally supplied through the foods we eat.
Basically, the nutrients which are found in our food are divided into two categories: Macronutrients and micronutrients.
These are proteins, fat, and carbohydrates that form a large bulk of the food.
These are vitamins and minerals. They are called micronutrients because they are required in small amounts which may vary from a fraction of a milligram to several grams.
Contribution of Macronutrients in total energy intake in balance diet food:
1. Protein = 7 to 15%
2. Fat = 10 to 30%
3. Carbohydrate = 65 – 80%
Classification of foods
A. On the basis of origin
1. Foods of animal origin, e.g., Milk, meat, fish, eggs etc.
2. Foods of plant origin, e.g., rice, maize, wheat, sugarcane etc.
B. On the basis of biochemical composition
C. On the basis of functions.
1. Body building foods, e.g., milk, meat, poultry, fish, eggs, pulses, groundnuts etc.
2. Energy giving foods, e.g., cereals, sugars, roots, fats and oils.
3. Protective foods, e.g., vegetables, fruits and milk.
D. On the basis of nutritive value.
1. Cereals and millets
2. Pulses (legumes)
4. Nuts and oilseeds
6. Animal foods
7. Fats and oil
8. Sugar and jaggery
9. Condiments and spices
10. Miscellaneous foods.
- Carbohydrates are energy-giving components of food.
- It is the major constituent of energy intake.
- Carbohydrate is a macronutrient and the simplest unit if carbohydrate is monosaccharides.
- The carbohydrate reserved (glycogen) in the adult body is 500 gm.
Sources of carbohydrates are:
A. Starch: cereals, roots, rice, potatoes, tubers etc.
B. Sugar: sugarcane, monosaccharides, disaccharides
C. Cellulose: indigestible, no nutritive value.
Functions of carbohydrate
1. It provides energy for various daily activities of our body.
2. Essential for oxidation of fats.
3. It helps on the synthesis of certain non-essential amino acids.
4. Form structural components of our cell.
5. Dextrose (glucose in solution in dextrorotatory form) is frequently used in medical practice.
Daily recommendations for carbohydrates.
Adult man: 2900 kcal/day
Adult woman: 2200 kcal/day
Pregnant women: 2500 kcal/day
Children: 1700 kcal/day
Carbohydrate and diseases
1. The disease associated with carbohydrates are: Diabetes mellitus, Glycogen storage diseases, galactosemia, lactose intolerance…etc.
2. The reduction in the carbohydrate diet reduces stamina.
4. Body weakness due to its deficiency.
5. Muscle fatigue, muscle cramps also occur due to its deficiency.
- Proteins are complex organic nitrogenous compounds composed of carbon, hydrogen, oxygen, nitrogen, and Sulphur in varying amounts.
- Proteins contain 16% of nitrogen.
- Proteins constitute 20% of body weight.
- Proteins are composed of smaller units or building blocks of protein is called Amino acids linked together by peptide bonds.
- Amino Acids are of two types: essential and non-essential amino acids.
- Humans require 20 amino acids among which 10 are essential amino acids (can’t be synthesized in the body and thus required in diet). While the other 10 are non-essential amino acids.
Sources of protein
A. Animal sources: milk, meat, eggs, fish…etc.
Egg protein is considered as best among the food protein having high biological value and digestibility.
B. Plant sources: pulses, cereals, beans, nuts, soybeans etc.
Soybean has the highest protein content.
Daily requirements of proteins
- Adult males and females: 1gm/kg/day
- Pregnancy: Additional 10 – 15 gm/day
- Infant: 1.15 – 1.7 gm/kg/day
- Children (1 -9 years): 1.1 – 1.3 gm/kg/day.
Functions of protein.
1. Protein is the body building food.
2. Protein helps in the repair and maintenance of body tissues.
3. Protein helps in the maintenance of osmotic pressure.
4. Protein helps in the synthesis of certain substances in our body like antibodies, plasma cells, haemoglobin, enzymes, hormones, and coagulation factors.
5. Proteins are the main structural components of the cytoskeleton
Protein and diseases
Protein Energy Malnutrition: It is the condition caused due to lack of protein and calories in the diet. It is of two types i.e., Marasmus and kwashiorkor. It is associated with:
2. Fatty liver
3. Skin hair and nail problems.
4. Loss of muscle mass
5. Stunted growth in children
6. Greater risk of bone fractures
7. Increased severity of infections.
8. Greater appetite…..etc.
- Fats are the Chief storage form of energy in our body.
- Fats are solid at room temperature of 20°C while oils are liquid.
- Fats are made up of fatty acids and glycerol.
Lipids are of 4 types.
1. Simple lipids. E.g., oils and waxes…etc.
2. Complex or compound lipids. E.g., lipoproteins (HDL, LDL, VLDL), lecithin, cephalin….etc.
3. Derived lipids. E.g., fatty acids and glycerol are derived forms of lipids. Fatty acids are of two types i.e., essential fatty acids (Linoleic acid, linolenic acid and Arachidonic acid) and non-essential fatty acids (palmitic acid)
4. Miscellaneous lipids. E.g., vitamin E, carotene, shark liver oil, vitamin K ..etc.
A. Animal fats: Ghee, butter, milk, egg., Fish oil, soya bean oil etc. Animal fats mostly contains saturated fatty acids except fish oil which contains mono and polyunsaturated fatty acids.
B. Vegetable fats: Groundnuts, mustard, coconut, palm oil…. etc. Vegetable fats contain polyunsaturated fatty acids except for coconut and palm oil which contain a high percentage of saturated fatty acids
C. Others: invisible fat in cereals, pulses, nuts, vegetables.
1. Fats are high energy giving foods.
2. Acts as vehicles for fat-soluble vitamins i.e., Vitamin A, Vitamin D, vitamin E and Vitamin K.
3. Fats are the precursors for different steroid hormones.
4. Fats supports viscera like the heart, kidney and intestine.
5. Fats beneath the skin provides insulation.
6. Cholesterol is the major component of cell membranes that acts as protection.
Daily recommendations for fat
- Total fat intake, 20-30% of total energy intake (at least 20%energy is consistent with good health).
- Saturated fatty acids, less than 10% of total energy intake.
- PUFAs, 6-10% of total energy intake (minimum of 6%)
- Trans fatty acids should be less than 1% of total energy intake.
- Cholesterol should be less than 300 mg a day.
Fat and diseases
A. Obesity due to excess fat intake.
B. Phrynoderma: due to deficiency of essential fatty acids and characterized by rough and dry skin.
C. Coronary heart disease due to increased cholesterol level.
- Vitamins are a class of organic compounds categorized as essential nutrients.
- Vitamin may be regarded as the non-energy producing organic compounds required in the diet in a small amount to perform specific biological functions for normal maintenance of growth and health of the organisms.
Vitamins are divided into 2 groups:
A. Fat-soluble Vitamins – It is 4 types:
1. Vitamin A(Retinol)
2. Vitamin D(Cholecalciferol)
3. Vitamin E(Tocopherols)
4. Vitamin K(Phylloquinone)
B. Water soluble Vitamins – It is of 2 types:
1. Vitamin C (Ascorbic acid)
2. Vitamin B complex
a. Vit B1 (Thiamine)
b. Vit B2 (Riboflavin)
c. Vit B3 (Niacin)
d. Vit B4 (Pantothenic acid)
e. Vit B6 (pyridoxine)
f. Vit B7 (Biotin)
g. Vit B9(Folic acid)
h. Vit B12(Cyanocobalamin)
1. Vitamin A.
Sources: Liver oil, carrot, butter, cheese, spinach, green leaves, ripe mango, egg, papaya, tomato, fish, cow milk, orange…etc
Man: 600 mcg / day
Women: 600 mcg / day
Pregnant women: 800 mcg / day
Lactating women: 950 mcg / day
Infants: 350 mcg / day
Children: 400 – 600 mcg / day
Functions of vitamin A
1. Vitamin A is the component of rod and cons cells of the eye so help in vision
2. Helps in spermatogenesis in males and menstrual cycle in females.
3. Helps in cholesterol synthesis.
4. Important in protein synthesis.
5. Maintenance of Germinal epithelium.
6. Acts as an antioxidant to prevent coronary artery disease, cataracts etc.
1. Night blindness
3. Bitot’s spot
4. Conjunctival xerosis
5. Corneal xerosis
7. Growth impairment…. etc.
2. Vitamin D (Sunshine Vitamin/Kidney Hormone)
- Vitamin D also called an anti-rachitic factor, is a group of sterol compounds that are required as accessory food factors in individuals not exposed to sunlight.
- The nutritionally important form of Vitamin D is Calciferol (vitamin D2) which may be derived by irradiation of the plant sterol and cholecalciferol (vitamin D3) is preformed vitamin D which is found in animal fats and fish liver oils.
- It is synthesized in the skin and is then metabolized to active metabolite calcitriol (1, 25 dihydroxy cholecalciferol) in the liver and kidney.
- It is found only in food of animal origin.
- Fish liver oils are the richest source.
Halibut liver oil (richest)>Cod liver oil (2nd richest)> Shark liver oil>fish fat> Egg Butter>Milk
Recommended daily allowance (RDA):
Normal infants: 200 IU (5 mcg/day)
Children: 400 IU (10 mcg/day)
Functions of vitamin D
- In intestine: promotes intestinal absorption of calcium and phosphorus.
- In bone: Stimulates normal mineralization, enhances bone resorption, affects collagen maturation.
- Kidney: Increases tubular reabsorption of calcium.
- Others: Permits normal growth.
Rickets (in children)
Osteomalacia (In Adults)
3. Vitamin E (Tocopherol/Beauty Vitamin)
- Vitamin E is widely distributed in foods. The richest sources are vegetable oils, cottonseed, sunflower seed, egg yolk and butter.
- Plays roles as anti-oxidants
- Role infertility is also called an anti-sterility vitamin.
- A high dose of vitamin E appears to be toxic.
- RDA: 8 to 10 mg tocopherol per day (o.8 m8/gm or essential fatty acids).
4. Vitamin K
- Vitamin K occurs in at least two major forms: vitamin K1 and vitamin K2.
- Vitamin K1 is found in fresh green vegetables (dark green), fruits.
- Vitamin K2 is synthesized by intestinal bacteria, which usually provide an adequate supply in man.
- It plays role in the production and release of certain coagulation factors (Factors VI, VII, IX, X).
- Daily requirement: 0.03 mg/Kg for adults.
5. Vitamin C(Ascorbic acid)
- It is the most sensitive of all vitamins to heat.
- Important Source: Amla (richest source)> Guava> Cabbage> Orange> Spinach>Tomato> Potato
- RDA: 40mg/day for adults
- Deficiency: Scurvy, Bleeding gums, swollen gums, subcutaneous bruising, or bleeding into the skin or joints, delayed wound healing, anaemia and weakness.
6. Vitamin B complex
A. Vitamin B1: (Thiamine)
- Thiamine is a water-soluble vitamin.
- Thiamine pyrophosphate (TPP) acts as a coenzyme inactivation of enzymes involved in the oxidative pathway for glucose.
- Source: Whole grain cereals, wheat, gram, pulses, milk, meat fish. vegetables and fruits.
- Loss of thiamine occurs in rice during the process of milling, also during the washing and cooling of rice.
- Thiamine is lost from fruits and vegetables in storage.
- The body content of thiamine is placed at 30 mg
- Recommended daily allowances: 1 to 1.5 mg/day for adults and 0.2mg/day for infants and 0.5 mg/day for children.
i. Dry beriberi: Nerve involvement (Peripheral neuritis)
ii. Wet beriberi: Heart involvement (Cardiac beriberi)
iii. Infantile beriberi: In infants between 2 and 4 months of age
b. Wernicke’s encephalopathy:
Seen often in alcoholics characterized by ophthalmoplegia, polyneuritis, ataxia and mental deterioration.
B. Vitamin B2 (Riboflavin)
- It has a fundamental role in cellular oxidation.
- It plays an important role in maintaining the integrity of the mucocutaneous structure
- Sources: milk, eggs, liver, kidney and green leafy vegetables.
- Germination increases the riboflavin content of pulses and cereals.
- Deficiency: angular stomatitis, cheilosis, glossitis, impaired neuromotor functions.
- Requirements: 0.6 mg per 1000 kcal of energy intake.
C. Niacin/Nicotinic Acid (vitamin B3)
- Niacin is essential for the metabolism of carbohydrates, fat and protein.
- Also essential for normal functioning of the skin, intestinal and nervous systems.
- Sources: Liver, kidney, meat, poultry, fish, legumes and groundnuts.
- Requirements: 6 mg/1000 kcal of energy intake.
- Deficiency of niacin causes Pellagra which is characterized by 4D’s: Diarrhea, dermatitis, dementia and death.
D. Pantothenic Acid (B5)
- Plays role in the biosynthesis of corticosteroids.
- The daily requirement is 10 mg.
E. Pyridoxine (B6.)
- Sources: Milk, liver, meat, egg yolk, fish, legumes and vegetables.
- Deficiency: Peripheral Neuritis.
- Requirements: 2 mg/day for adults and 2.5 mg/day for pregnant and lactating mothers.
F. Folate (B9)
- It is needed for the normal development of blood cells in the marrow.
- Sources: Liver, meat, dairy product, eggs, milk, fruits, cereals, leafy vegetables etc.
- Deficiency: Megaloblastic Anemia, gastrointestinal disturbances like diarrhoea, distension, flatulence.
- Requirements: 200 meg/day for healthy adults, 500 mcg/day for pregnant, 300 mcg/day for lactating, 80- 120 mcg/day for children.
G. Vitamin B12 (Cyanocobalamin)
- It cooperates with folate in the synthesis of DNA.
- Sources: Liver, kidney, meat, fish, eggs, milk and cheese.
- It is absent in foods of vegetable origin.
- Deficiency: Megaloblastic Anemia, pernicious anemia.
- Requirement: 1 mcg/day for adults, 1.2 mcg for pregnancy, 1.5 mcg/day for lactating, 0.2 mcg/day for infants and children.
- Minerals are required for the growth, repair and regulation of vital body functions.
- Major minerals: Calcium, Phosphorus, sodium, potassium, magnesium.
- Trace elements: Iron, iodine, Fluorine, Zinc, copper, cobalt, etc. they required in small quantities of less than a few milligrams per day.
- Plays many vital functions including the formation of bones, teeth, coagulation of blood, contraction of muscles, milk production etc.
- Sources: Milk, eggs, fish, cereals etc.
- Requirements: 600 mg/day for adults, 1200 mg/day for pregnant and lactating mothers, 500 mg/day for infants and 600 mg/day for children.
1. Osteomalacia, osteoporosis
2. Improper growth of body
3. Tetany, muscle twitches.
- The adult human body contains between 3-4 g of iron of which about 60-70% is present in the blood (Hb iron) and the rest (1 to 1.5 g) is storage iron.
- Each gram of haemoglobin contains about 3.34 mg of iron.
- Iron is mostly absorbed from the duodenum and upper small intestine in a ferrous state.
- Iron absorption is enhanced by Ascorbic acid and citrous foods and inhibited by phosphates.
1. Formation of haemoglobin, brain development and function.
2. Regulation of body temperature, muscle activity and catecholamine metabolism.
3. Iron is also the component of myoglobin, cytochromes, catalase and certain enzymes.
4. Major function of iron is “oxygen transport and cell respiration.
A. Haem iron: Liver, meat, poultry, fish.
B. Non-haem iron: Cereals, green leafy vegetables,
legumes, nuts, oil/seeds, dried fruits.
- It is required for synthesis or thyroid hormones T4 and T3 lodine is essential in minute amount for normal growth and development and well-being or al humans.
- Sources: Seafood (sea fish, sea salts), cod liver oil etc.
- Requirements: Adults: 150 mcg/day and pregnancy: 250 mcg/day.
- Deficiency: iodine deficiency disorders (IDD) refer to all the effects of iodine deficiency on human growth and development which can be prevented by correcting iodine deficiency.
a. Hypothyroidism: Hypofunction of the thyroid gland causing decreased basal metabolic rate.
b. Retarded physical and mental growth & development.
c. Goiter: Goiter is the enlargement of the thyroid gland causing swelling in the front of the neck.
d. Myxedema: Results from hypofunction of the thyroid gland more commonly in females.
e. Cretinism: Caused by decreased thyroid secretion.
- Sources: meat, milk, fish, vegetables.
- Deficiency: growth failure, sexual infantilism, alopecia, immune disorder, low birth weight, 1UFD and preterm delivery.
- Requirements: 12 mg/day for adult men, 10 mg/day for adult female, 10 mg/day for children and 5 mg/day for infants.
- Zinc supplementation in combination with ORS is significant in reducing the severity of acute and persistent diarrhoea and increasing the survival rate. (Recommended dose is 20 mg for more than 6 months age and 10 mg for less than 6 months for 14 days).