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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:
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.
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.
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.
• Supplies energy
• Protein sparing function
• Oxidation of fats
• Regulating blood glucose
• Facilitates bowel movements
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.
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.
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)
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.
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.
Animal sources: eggs, milk and milk products, fish, meat.
Plant sources: pulses, cereals, dry fruits, beans nuts etc.
• 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.
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.
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
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.
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
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
• 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
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 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
It is otherwise called as antihemorrhagic vitamin.
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
These vitamins are
essential for many metabolic functions of the body. These are daily required in
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.
Beriberi- condition in which there is a severe muscle wasting, growth retardation in children, neurological disturbances and frequent infection.
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.
• Glossitis- Ulceration of the tongue.
• Angular stomatitis- Cracks at the corner of the lips.
• Corneal ulceration
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
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
Anti dermatitis factor
Daily requirements: 10mg
Eggs, liver, yeast, many fish and vegetables.
• Necessary for metabolic functions
Dermatitis, hair loss
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
Anaemia, nervousness, insomnia, oedema (Water retention), mental depression. Muscle weakness, tooth decay.
Arm and leg cramps, Skin lesions and skin disorder.
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.
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.
• 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
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
• Pernicious anemia
• Neurological and mental disturbances
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
Scurvy- Painful swelling of gums and joints. Multiple hemorrhages specially in gums, skin and mucus membrane Delayed wound healing.
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.
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.
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.
· 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.
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.
· 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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