Functions, Sources, Daily requirements, Deficiency Syndrome - Nutrients | 12th Nursing : Chapter 4 : Nutrition

Chapter: 12th Nursing : Chapter 4 : Nutrition


The substances which are present in the food and consumed in our body for its vital functions are called nutrients.


The substances which are present in the food and consumed in our body for its vital functions are called nutrients. According to the World Health Organization (WHO), these nutrients must come from food, and they are vital for disease prevention, growth, and good health. There are several constituents such as:


I. Carbohydrates

Carbohydrates are the chief sources of energy (Providing 4 Kcals/gm). Carbohydrates are cheap and readily available from food. There are three different kinds of carbohydrates. They include starch, sugar, and fibre. We do not get calories from fibre because our bodies do not break down fibre during digestion.

Classification of Carbohydrates

Monosaccharides: these are the simplest form of carbohydrates containing simple sugar molecule. Example: Glucose, Fructose and Galactose.

Disaccharides: These carbohydrates composed of two units of Monosaccharides. Example: Sucrose, Lactose and Maltose.

Polysaccharides: these are the complex sugars containing numerous units of monosaccharide molecules. Example: Glycogen, Cellulose and Pectins.

Daily requirements

Carbohydrate intake should be in the range of 300-500gm (50%- 70%) out of the total energy intake for adults and 40-60% for children.

Sources:  All sugars, jaggery, honey, pulses, whole grains, cereals, grains, rice, fruits, milk, yogurt, beans, roots and tubers such as potatoes, beet root etc.

Functions of Carbohydrates

            Supplies energy

            Protein sparing function

            Oxidation of fats

            Regulating blood glucose

            Facilitates bowel movements

Digestion and absorption of Carbohydrates

Salivary amylase aids digestion of starch in themouth.Mostofthedigestionofcarbohydrates takes place in the small intestine. Carbohydrates are absorbed into the blood stream as glucose, Galactose and fructose. By way of the capillaries of the villi, the simple sugars enter the portal circulation and transported to the liver.

Dietary Fibre

The carbohydrates (E.g, pectin, cellulose, hemicellulose) and some non carbohydrates substances (e.g. lignin) are collectively called as dietary fibre. Fibre is found in vegetables, fruits and grains. It resists digestion.

Significance of Fibre

High fibre diet plays an important role in prevention and management of constipation (Inability to pass motion/ lack of bowel movement)

Fibre also helps to reduce blood cholesterol

Helps to prevent blood glucose level after food (Post prandial blood glucose)


II. Proteins

Proteins are the indispensible constituents of the diet. Proteins are made up of amino acids. Amino acids are needed for replacement and growth of the body parts.

Amino acids are classified as essential and non essential amino acids. Essential amino acids cannot be synthesized by the body and must be taken through foods whereas non essential amino acids can be synthesized by the body.

Daily requirements

The ICMR recommends 1gm of protein/ Kg of body weight for adults.

The amount of protein should be increased for children, pregnant and lactating mothers by 1.5- 2 g/kg body weight.

Sources of Protein

Animal sources: eggs, milk and milk products, fish, meat.

Plant sources: pulses, cereals, dry fruits, beans nuts etc.

Functions of Proteins

            Protein helps in synthesis of enzymes, immunoglobulin, plasma proteins and hormones in the body

            Protein helps in growth and repair of body tissues

            Proteins are secondary sources of energy during deficiency of carbohydrates and fats. (Provides 4 Kcals/gm)

            Proteins help in forming haemoglobin

            Proteins help in antibody formation

Digestion and absorption: The hydrolysis of proteins in the gastro intestinal tract is accomplished by proteases secreted in gastric juice and pancreatic juice and also by proteases present in the intestinal mucosa.


III Fats

Fat is deposited as adipose tissue in the body and perform essential functions in the body. Fats are composed of fatty acids and contain oxygen, carbon and hydrogen.

Classification: Fats are classified in to two types:

saturated fat and unsaturated fat.

a) Saturated Fat: These have full number of hydrogen atoms. These are from animal sources. Example: butter, Ghee and vanaspati oil.

b) Unsaturated Fat: These contain one, two or more double bonds of fatty acids. These are extracted from vegetable sources. Example: Groundnut oil, soyabean oil, sunflower oil.

Daily Requirements

15-20% of total calorie requirements should be from fat


Animal sources:  Fish, egg, meat, milk and milk products.

Plant sources:  oil seeds (Groundnut, mustard, cotton seed and coconut oil), nuts.


            Supplies energy (9 kcals/ gm)

            Improve the palatability of food (flavor and taste)

            Supports body organs like liver and kidneys

            Provides insulation and thermoregulation against cold

            Provides essential fatty acids which helps in growth, promotion and maintenance of skin integrity

            Helps in formation of hormones in the body

            Helps in transportation of fat soluble vitamins

Digestion and absorption

There is no digestion of fats in mouth and very little in stomach. In the small intestine, presence of fat stimulates cholecystokinin and secretin which further stimulates pancreatic juice and bile. Food mixes with bile and emulsified. Pancreatic lipase hydrolyses and yields fatty acids and monoglycerides. These pass to small intestine and combined with intestinal lumen and absorbed in to blood stream.


IV. Vitamins

vitamins are complex chemical substances required by body in very small amounts. Vitamins in food are for the protection and regulation of body functions.

 Vitamins are divided in to two major groups

 Fat soluble vitamins- Vitamin-A, D, E and K

 Water soluble vitamins- Vitamins of B group and vitamin C

Fat Soluble Vitamins



The chemical name is Retinol. Found in foods of both plant and animal origin.

Daily requirements: 0.4-1 mg Sources

Green leafy vegetables and yellow orange fruits and vegetables like mango, papaya, pumpkins and carrots are good sources of β-carotene.

Butter, whole milk, egg, liver and fish are richest sources.


            Necessary for the health of the eyes.

            Maintenance of the normal epithelial tissues of the body.

            Necessary for growth and proper utilization of protein

Deficiency Syndrome

 Decreased resistance to infection Dry scaly skin

 Night blindness (Inability to see in dim light)

 Xerophthalmia- dry eye

 Bitot’s spots- Greyish, rough and raised patches on conjunctiva

 Keratomalacia- Softening of the cornea.

 Stunted Growth



Vitamin  D  is  synthesized  by  sunlight.

Vitamin D is essential for bone growth.

Daily requirements: 400 IU Sources 

Generated in the skin by action of ultra violet rays of sunlight

Food sources are milk, butter, cheese, egg, fish and fish liver oils, and foods which have been fortified by addition of vitamin D.


            Increases intestinal absorption of calcium and phosphates

            Mineralization of bones

Deficiency Syndrome

Rickets in children- Bony deformities in growing children due to defective mineralization of the growing bones. Bones become soft and bend under pressure.

Osteomalacia- Generalized bone pain in adults especially in women.


Vitamin E

Vitamin E is an antioxidant and formed up of chemical substance called tocopherols.

Daily requirements: ICMR recommends 0.8 mg/ g of essential fatty acids.


Milk, oils, eggs, leafy vegetables, papaya, grains, nuts.


            Antioxidant (Prevents the formation of oxidative free radical)

            Co factor in electron transport

            Prevents or delays the ageing

Deficiency syndrome: Sterility, muscle wasting with weakness


Vitamin K

It is otherwise called as antihemorrhagic vitamin.

Daily requirements

WHO suggested RDA of 55 μg per day for adults.


Green leafy vegetables, cereals,  fruits. Synthesized by bacteria in gut.


Important component in blood coagulation

Helps in formation of blood clotting factors

Deficiency Syndrome: Alteration in blood clotting mechanism


II. Water Soluble Vitamins

These vitamins are essential for many metabolic functions of the body. These are daily required in diet.


Vitamin B1- Thiamine

Thiamine is essential for the normal metabolism of carbohydrates and fats. It is necessary for the transmission of nerve impulses.

Daily requirements: 0.5 to 2 mg


whole grain cereals, wheat, ragi, pulses (dhal), vegetables and potatoes, green leafy vegetables. Meat, fish, liver and eggs.


Helps in carbohydrate utilization.

Maintenance of appetite and digestion.

Deficiency Disorder

Beriberi- condition in which there is a severe muscle wasting, growth retardation in children, neurological disturbances and frequent infection.


Vitamin B2

Vitamin B2, also known as riboflavin, is one of the eight B-complex vitamins. It is essential for the health of skin and for normal vision.

Daily requirements: 0.6 mg/ 1000 Kcal


Riboflavin is found in eggs, nuts, dairy products, meats, broccoli, sprouts, wheat germ, wild rice, mushrooms, soyabeans, green leafy vegetables and whole grain and enriched cereals and bread. Riboflavin also synthesized by bacteria in intestine.


It helps the body break down carbohydrates, proteins and fats to produce energy.

It allows oxygen to be used by the body.

Deficiency Syndrome

 Glossitis- Ulceration of the tongue.

 Angular stomatitis- Cracks at the corner of the lips.

 Corneal ulceration


Vitamin B3

Niacin is one of the B-complex nutrients; it can be synthesized in body.

Daily requirements: 10-15 mg


Found in appreciable amounts in liver, yeast, meat, legumes, peanuts and whole cereals.

Foods that are good sources of tryptophan are animal protein and vegetable protein.


Helps in normal functioning of skin, intestinal tract and nervous system

Deficiency Syndrome

1. Pellagra- Three conditions are

            Dermatitis -dark, dry and scaly skin

            Diarrhea- due to atrophy of intestinal wall

            Dementia-Memory Loss

2. Glossitis, mental disorders


Vitamin B5- Pantothenic acid

Anti dermatitis factor

Daily requirements: 10mg


Eggs, liver, yeast, many fish and vegetables.


            Necessary for metabolic functions

Deficiency Syndrome

Dermatitis, hair loss


Vitamin B6

This vitamin B6is otherwise known as pyridoxine. It is stored in muscle but found in tissues throughout the body.

Daily requirements: 1.5-2 mg for normal adults.


Whole grains, legumes, bananas, potato, liver, kidney and other meats, fortified breads and cereals. Sunflower seeds, soya beans, walnuts and yeast are the richest sources of pyridoxine among plant foods.


            Production of red blood cells

            It is readily absorbed from intestines

            Improves immunity

            Improves nervous system function

            Reduce muscle spasms, cramps and numbness

            Maintains proper balance of sodium and phosphorous in the body

Deficiency Syndrome

Anaemia, nervousness, insomnia, oedema (Water retention), mental depression. Muscle weakness, tooth decay.

Arm and leg cramps, Skin lesions and skin disorder.


Vitamin B7

Otherwise known as Biotin. It is associated with carbohydrates metabolism.

Daily requirements: Traces


Egg yolk, liver, kidney, tomatoes, vegetables, legumes and cereals.


It is needed for protein and fatty acid synthesis

Deficiency syndrome: Dermatitis, hair fall.

Folic acid

Vitamin B9 includes both folate and folic acid and is important for several functions in the body.

Daily requirements: 0.4mg


Fish, mutton, liver, egg, chicken, green leafy vegetables, pulses, lentils, beans, sunflower seeds, beets, broccoli, spinach, orange juice, tofu, fish, meat, fortified cereals, milk, cheese, eggs, oysters, crab etc.,


·           Folic acid helps the body to convert carbohydrates into glucose, which is used to provide energy.

·           Folic acid helps in building of antibodies which prevent and heal infections.

·           Regulates blood cells formation.

Deficiency Syndrome

 A recent study connected folic acid deficiency with autism

 Megaloblastic anemia


 Low birth weight babies

 Congenital defects in the child- cleft lip and cleft palate


Vitamin B12-Cyanocobalamine

This vitamin is destroyed by heat.

Daily requirements: 1-3 μg


Foods of animal origin, also synthesized by bacteria.


·           DNA Synthesis

·           Stimulates and promotes maturation of RBC’s

Deficiency Syndrome

 Pernicious anemia


 Neurological and mental disturbances


Vitamin C

Vitamin C is also known as ascorbic acid.

It is an antioxidant and water soluble vitamin.

Daily requirements: up to 40 mg

Sources: Citrus fruits (amla, guava, lemon, orange, tomato), green leafy vegetables.


·           Helps in wound healing

·           Prevents bleeding

·           Antioxidant

Deficiency Syndrome

Scurvy- Painful swelling of gums and joints. Multiple hemorrhages specially in gums, skin and mucus membrane Delayed wound healing.


V. Minerals

These are the inorganic compounds in micro quantities which are essential for many vital functions of the body. The minerals constituent of the body amounts to 4.3 to 4.4 %, largely in the skeleton.

General Functions of Minerals

As constituents of hard tissue. (eg.) calcium and phosphorus in bone and teeth.

As constituents of soft tissue. (eg.) Sulphur and phosphorus.

As constituents of substances assisting in the regulatory function of the body (eg.) salts in solutions influence nerve and muscle action.

Some of the essential mineral salts are sodium, potassium, calcium, phosphorus, magnesium, iron and iodine.



Calcium is most important for children and pregnant women.

Calcium is important component in bones and enamel of teeth. 99% of body calcium is found the bones.

Sources: milk and its products, green leafy vegetables, bones of meat, fish, pumpkin, coconut, dry fruits, cereals.

Daily requirements: 400- 500mgm


·           Formation and maintenance of bones and teeth

·           Coagulation (Thickening) of blood

·           Muscle contraction



Sodium is essential for many body activities. It is taken in the diet as salt.

Sources: Common salt, sodium chloride is also found in certain foods like fish, meat, eggs and seasoned foods.

Daily requirements: 8-10 gms


·           It helps in transmission of nerve impulses

·           Maintenance of body fluids and electrolytes balance

·            Smooth functioning of nerves, muscles and body cells



Most of the potassium present inside the cells.

Sources: Fresh vegetables, citrus fruits, milk, guava and amla.


·           Involved in various biochemical activities of the cells.

·           Transmission of nerve impulses.

·           Maintenance of electrolyte balance and contraction of muscles.

Daily requirements: 2-5 gms



Most of the phosphorus present in the bones as inorganic form. Few amount resent inside the cells.


Whole grain cereals and flours, legumes, oatmeal, cheese, nuts, fish


·           Gives rigidity to bones and teeth

·           Regulates pH of the blood and urine

·           Important in energy metabolism

·           Phosphorus compounds are necessary for carbohydrate metabolism and for the calcification of bones and teeth

·           Needed for transport of fatty acids



The amount of iron present in the adult human body is very small, but it is very important substance and essential for the maintenance of life. 75% of total body iron present in the blood.

Sources: Liver, meat, fish, eggs, cereals, pulses, green leafy vegetables, dry fruits, jaggery, certain beans.

Daily requirements: 25-40 mg


·           Component of hemoglobin and myoglobin

·            Helps in oxygen transport and cellular respiration



Iodine is considered as an important for maintaining metabolic rate.

Sources: Iodized salt, salt water fish, milk, meat cereals and green leafy vegetables.

Fortification of common salt with potassium iodate is a recommended method of making iodine easily available.

Daily requirements: 01.05 mg


·           Iodine is an important constituent of thyroxine, the hormone secreted by the thyroid gland

·            Iodine is responsible for the regulation of physical growth



Human body contains about 25gms of magnesium. Half of it is present in bones and in combination with phosphate and carbonate and about 1/5th in soft tissues.


Constituent of bones and teeth, coenzymes in general metabolism, smooth muscleaction.

Sources of Magnesium: Dairy products (excluding butter) fresh green vegetables, meat, nuts, sea food and legumes are good sources of magnesium.


Other Inorganic Elements

Copper: Functions with iron in the formation of haemoglobin.

Manganese: Has a similar effect though less marked than copper.

Cobalt: It is present in vitamin B12 which is also necessary for the formation of haemoglobin.

Zinc: Is found mainly in pancreatic tissue and may have an important part to play in the storage of insulin in the gland.

Clinical Significance of Minerals

·           Calcium: Deficiency of calcium in the body precipitates rickets in the children and osteomalacia in adults.

·           Iron: Reduced level or lack of iron causes anemia, certain hormonal changes in women.

·            Iodine: Lack of iodine in the body leads to enlargement of thyroid gland called as goiter.


VI. Water

Water is an important component with diet as it performs many vital functions in the body and hence is a part of balanced diet. Water makes up to 70% of total body weight inhuman beings. Water should be taken in enough quantities to prevent dehydration.

Distribution of Body Water

Functions of Water

·            Water is a major constituent of blood and tissue fluid

·            It helps in transport of many substances from one compartment to another

·            Provision of the moist internal environment required by all living cells

·            Participation in all the chemical reactions occurring extracellularly and intracellularly

·            Regulation of the body temperature


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