Nutrition and Diet plan health tips facts know more about essential vitamins minerals protein fat carbohydrate water to be taken in Diet
By Live Dr - Sun Jun 20, 8:53 pm
All living organisms need matter to build up the body
and energy to operate the metabolic reactions that sustain
life. The materials which provide these two primary
requirements of life are called nutrients or food. The sum
of the processes by which the living organisms obtain
matter and energy is termed nutrition. All the processes
involved in the taking in and utilization of food substances
by which growth, repair and maintenance of activities in
the body as a whole or in any of its parts are accomplished,
are included in nutrition.
Evolution of Nutrition
Nutrients in the food an animal consumes provide the
necessary chemicals for growth, maintenance and energy
production. Overall, the nutritional requirements of an
animal are inversely related to its ability to synthesize
molecules essential for life : the fewer such biosynthetic
abilities an animal has, the more kinds of nutrients it must
obtain from its environment. Green plants and photosynthetic
protists have the fewest such nutritional
requirements because they can synthesize all their own
complex molecules from simpler inorganic substances;
they are called Autotrophs. Animals, fungi and bacteria
that are called heterotrophs, cannot synthesize many of
their own organic molecules and must obtain them by
consuming other organisms or their products. Animals,
such as rabbits, that subsist entirely on plant material are
called hervivores. Carnivores, such as hawks, are
animals that eat only meat. Omnivores, such as humans,
eat both plant and animal matter.
Modes of Nutrition
Autotrophic or Holophytic Nutrition
All green plants and certain protists (Euglena Viridis)
have evolved a mechanism to directly use the energy of
sunlight for preparing organic food in their own body from
simple inorganic materials. This process of making food is
called photosynthesis and the organisms capable of it are
Some bacteria have developed a technique to
capture energy released during oxidation of inorganic
chemical substances and prepare organic food with its
help. They are known as chemotrophs and the process
as Chemosynthesis. Nitrifying bacteria, Nitrosomonas
and Nitrobacter are chemotrophs.
Since, both phototrophs and chemotrophs do not take
organic molecules produced by other organisms, they are
called autotrophs. Their modes of feeding are together
referred to as autotrophic nutrition. Since, it is characteristic
of plants, it is also called holophytic nutrition.
Animals, fungi, some protists (Amoeba) and many
bacteria cannot utilize sun energy. They use chemical
bond-energy of organic molecules synthesized by other
organisms in building their own organic molecules. Such a
mode of feeding is termed heterotrophic nutrition and the
organisms having it are called heterotrophs.
Heterotrophic Nutrition of three following types :
1. Saprotrophic Nutrition—Many organisms absorb
fluid food through the body surface. This is called
saprotrophic nutrition. Bacteria and fungi flourish on dead,
decaying organic matter of both plant and animal origin.
They secrete digestive enzymes onto this matter. The
enzymes hydrolyze the organic matter into simple soluble
products that are then absorbed. This method of taking up
organic food is known as saprophytic nutrition. Some
parasitic protists, such as Trypanosoma and a few invertebrates,
such as tapeworms, live in a medium that contains
simple organic compounds ready for absorption and
straightway absorb them. This mode of taking up organic
compounds is termed saprozoic nutrition.
2. Holotrophic Nutrition—Majority of invertebrates
and all vertebrates take plant, animals or their products
through the mouth and break up the large organic
molecules into smaller ones in their own body with the
help of digestive enzymes. The simple molecules are then
absorbed into the cells and utilized. This mode of taking
organic food is called holotrophic nutrition. Since, it is
characteristic of animals, it is also called holozoic nutrition.
The animals may take plants, or other animals, or
both as food and are respectively called herbivores
(rabbit, cow), carnivores (lion, tiger) and omnivores
3. Mixotrophic Nutrition—Euglena carries an autotrophic
and saprotrophic nutrition at the same time. This is
called mixotrophic nutrition.
The Metabolic fates of nutrients in Heterotrophs :
The nutrients ingested by a heterotroph can be
divided into macronutrients and micronutrients. Macronutrients
are needed in large quantities and include the
carbohydrates, lipids and proteins. The micronutrients
are needed in small quantities and include organic
vitamins and inorganic minerals. Together, these nutrients
make up the animal’s dietary requirements. Besides these
nutrients, animals require water.
Calories and Energy—The energy value of food is
measured in terms of calories. A calorie is the amount of
energy required to raise the temperature of 1 g of water
1°C. A calorie, with small ‘c’, is also called a gram calorie.
A kilocalorie, also known as a calorie or kilogram calorie
(k cal), is equal to 1000 calories [kilojules (kJ = 4·1855 ×
A food’s calorie content is determined by burning it in
a bomb caloriemeter, a chamber surrounded by water.
When burning food is placed in the chamber, the energy
released raises the water temperature and the energy is
measured in kilocalories. Bomb calorimetry studies have
shown that 1 gram of carbohydrate yields 4·1 kilocalories,
1 gram of protein yields 4·3 kilocalories, 1 gram of fat
yields 9·3 kilocalories. These value explain why a fatty
diet may cause weight gain; fats supply more energy than
most people can use.
The Average Caloric Values of Macronutrients
Macronutrient Calories per gram
Macronutrients—With a few notable exceptions,
heterotrophs require organic molecules, such as carbohydrates,
lipids and proteins, in their diets. When these
molecules are broken down by enzymes into their
components, they can be used for energy production or
as sources for the ‘building blocks’ of life.
The major dietary source of energy for heterotrophs
is complex carbohydrates. Most carbohydrates originally
come from plant sources. This dietary need can be met by
various polysaccharides, disaccharides or any variety of
simple sugars (monosaccharides). Carbohydrates also
serve as a major carbon source for incorporation into
important organic compounds. Many plants also supply
cellulose, an indigestible polysaccharide, for humans and
other animals (with the exception of herbivores). Cellulose
is sometimes called dietary fibre.
Neutral lipids (fats) or triacylglycerols are contained in
fats and oils, meat and dairy products, nuts and avocados.
Lipids are the most concentrated source of food energy.
They produce twice the energy available from an equal
mass of carbohydrate or protein. Most heterotrophs have
an absolute dietary requirement for lipids, sometimes for
specific types. For example, unsaturated fatty acids (e.g.,
linoleic acid, linolenic acid and arachidonic acid) are
required by a variety of animals. Their most obvious
function is to act as precursor molecules for the synthesis
of sterols, the most common of which is cholesterol. The
sterols are required for the synthesis of steroid hormones
and incorporated into cell membranes. Other lipids
insulate the body of some vertebrates and help maintain a
The animal sources of protein include, for example,
eggs, meat of animals and milk. The plant sources
include, for example, beans, peas, and nuts. Proteins are
needed for their amino acids, which heterotrophs use to
build their own body proteins.
Micronutrients—Micronutrients are usually small
ions, organic vitamins, inorganic minerals and molecules
that are used over and over for enzymatic reactions or as
parts of certain proteins (e.g., copper in haemocyamin
and iron in haemoglobin). Even though they are needed in
small amounts, animals cannot synthesize them rapidly,
thus they must be obtained from the diet.
Major contents of food are carbohydrates, fats,
proteins, water, mineral salts and vitamins. According to
their utility in the body, the various nutrients of food can
be placed into the following three categories—
1. Energy producers—Oxidative combustion of
these substances (mainly carbohydrates and fats) yield
bioenergy required for performance of all biological
2. Body builders—These (mainly proteins) are the
major structural components of body and, hence, required
for growth and repair.
3. Metabolic regulators—These substances (vitamins,
water and mineral salts) control and regulate the
internal environment of body and metabolism.
These are carbon ‘hydrates’ (polyhydroxy aldehydes
and polyhydroxy ketones), i.e., compounds of carbon,
hydrogen and oxygen (1 : 2 : 1 ratio) with the ratio of
hydrogen and oxygen being the same as in water (H2O).
Obviously their empirical formula is (CH2O)n . These occur
in food as soluble sugars and insoluble starches.
Chemically, these are of three main categories, viz.,
monosaccharides, oligosaccharides and polysaccharides.
Monosaccharides—These are simplest, colourless,
soluble and sweet carbohydrates. Their molecules may
have three to seven carbon atoms. Monosaccharides
having five or six (pentoses or hexoses) carbon atoms in
their glucose, fructose, galactose and mannose.
Glucose is the most common and most important hexose
sugar. Animals mainly use it for energy production (main
fuel substance). Of the pentose sugars, most important
are ribose and deoxyribose, because these participate in
the composition of DNA and RNA.
Oligosaccharides and Disaccharides—When two
molecules of the same or different monosaccharides link
by a ‘glycosidic bond’, a disaccharide molecule is
formed. Disaccharides are also sweet and soluble sugars.
These are maltose (malt sugar) and sucrose (cane
sugar) of plants and lactose (milk sugar) of animals.
Maltose is formed from glucose monomers (a, 1-4 linkage),
sucrose from combination of glucose and fructose
(a, 1-2 linkage) and lactose from combination of glucose
and galactose (ß, 1-4 linkage). Amount of lactose is
highest in the milk of human mothers. Linkages of a few
(upto 10) monosaccharides are generally called oligosaccharides.
Polysaccharides—When several (more than 10)
monosaccharide molecules link by glycosidic bonds,
insoluble carbohydrate molecules, called polysaccharides
are formed. These are the polymers (C6H10O5)n of monosaccharide
units or monomers. Starch and inulin are
common polysaccharides found in plants but cellulose of
their cell wall is the most abundant structural polysaccharide
Glycogen is the common polysaccharide found in
Chitin of arthropod exoskeleton is nitrogenous polysaccharide.
Uses of Carbohydrates—The carbohydrate of the
food eaten, after being processed in the alimentary canal and liver, are supplied to the tissues as glucose, often
called blood sugar. The carbohydrates serve a variety of
1. As fuel—Carbohydrates form the major fuel in the
cells to provide energy for life processes. One gram of
carbohydrates on complete combustion in a bomb
caloriemeter yields 4·1 kilocalories of energy. This is
called caloric value of carbohydrates. One gram of food
carbohydrate on oxidation in the cells produces 4 k cal of
energy. This is known as the physiological fuel value of
carbohydrates. Carbohydrate form a better fuel than
proteins and fats because their molecules have relatively
more oxygen and, therefore, need less molecular oxygen
for oxidation that those of proteins and fats.
2. Reserve food materials—Carbohydrates form
storage products. If in excess, glucose is converted into
glycogen and stored in the liver and muscle cells. This
conversion is called glycogenesis. It may be changed
into fat and stored in liver, adipose tissue and
mesenteries. This change is termed lipogenesis. In case
the food provides inadequate glucose, reserve glycogen is
converted into glucose for energy production work. This
conversion is known as glycogenolysis.
3. Components of cellular compounds and organelles—
Pentose sugar ribose is a component of ribonucleic
acids (RNA) energy carriers, such as adenosine
triphosphate (ATP) and certain coenzymes, such
Nicotinamide Adenine Dinucleotide (NAD). Another
pentose sugar deoxyribose is a component of deoxyribonucleic
acid (DNA). The RNA and DNA are in turn components
of ribosomes and chromosomes respectively.
4. Formation of Amino Acids—Amino acids may be
formed from intermediates of carbohydrate ketabolism.
5. Heteropolysaccharides—These consist of modified
monosaccharide units. They form the following
important substances :
Anticoagulant heparin; blood group substances, such
as A, B and Rh antigens of erythrocytes. Lubricant hyaluronic
acid present in the synovial fluid of the joints,
cerebrospinal fluid and vitreous humor.
Protective coats, such as glycocalyx, that covers the
intestinal epithelium and mucus which covers all mucous
Luteinizing hormone that causes ovulation, formation
of corpus luteum and secretion of female sex hormone.
Cells can absorb only monosaccharides from tissue
fluid. Therefore, all disaccharides and polysaccharides of
food are broken down into their monomers in the gut
before being absorbed in blood. This is their digestion.
Since their synthesis is a condensation (= dehydration)
process, their digestion is ‘hydrolysis process’.
Three categories of lipids occur in animal food, i.e.,
simple, compound and derived.
Simple lipids—These are neutral or true fats and
compounds of carbon, hydrogen and oxygen but the ratio
of H2 and O2 is never 2 : 1 unlike water. A molecule of fat
is formed by linking a molecule of glycerol with three
molecules of fatty acids (aliphatic carboxylic acids) by an
ester-bond. These fats are, therefore, also called triglycerides.
This linkage is also a dehydration-condensation
reaction, yielding three molecules of water. Ghee, oils,
lard, butter etc. are common neutral fats. Waxes (such as
beewax) are also simple lipids. Most animal fats are
saturated and hence, solidify at low temperatures. Most
vegetable oils are unsaturated and, hence remain fluid.
Oxidative breakdown of fats yields more than double the
amount of energy yielded by glucose, because of their
poor oxygen contents. These can be stored in an almost
pure unhydrated form in large amounts in lesser space.
Hence, fats serve as the best storage of spare energy in
the form of ‘reserve stored food’. These are stored in
adipose tissues, which also serve for heat insulation.
Compound or Conjugated lipids—These lipids contain
traces of nitrogen, phosphoric acid, or carbohydrates.
Phosphoric acid containing phospholipids are components
of membrane system of cells. Of these lecithin and
cephalin are commonly found in liver, nervous tissue,
yolk and muscles. Carbohydrate containing lipids called
glycolipids, occur in cell-membranes of brain cells.
Derived fats—These are formed when neutral and
conjugated fats are hydrolysed. Hence, these are fat-like
alcohols, usually called lipoids or steroids. The most
common steroids are sterols. Cholesterol is the main
sterol found in blood plasma and cell membranes. Bile
acids, sex hormones, vitamin D, ergosterol, hormones of
adrenal cortex are examples of sterols.
Uses of fats—Fats serve a variety of functions :
1. Like carbohydrates, fats are also used as ‘fuel
substances’. Their caloric value is 9·4 k cal and
physiological fuel value is 9 k cal.
2. There are important food—reserves and produce
more energy on oxidation than glycogen.
3. Fat deposited in layers provides thermo-insulation
and protection against pressure.
4. Conjugated lipids are components of membrane
systems of cells, connective tissues and myelin of
Man can synthesize most of the fatty acids in his body
from the food taken. A few fatty acids are not synthesized
in body and must be present in the diet. These are called
essential fatty acids. They include linoleic, linolenic
and arachidonic acids. They are present in unsaturated
vegetable oils, such as groundnut oil, sunflower oil etc.
Proteins account for about 14% part of living and
75% part of dead and dried animal body. These are the
major components of the body and are more important for
anabolism (architecture, growth and repair of body), than
for ketabolism (energy production).
There are compounds of C, H2 and O2 but in addition,
these essentially contain about 16% nitrogen and may
also contain traces of sulphur, phosphorus, iodine, iron
Protein is polymer of very large or enormous molecular
mass, composed of one or more polypeptide chains
and whose monomers are amino acids, joined together (in
condensation reactions) by peptide bonds. In addition,
some have covalent ‘sulphur bonds’ formed by oxidation
between two cysteine radicals in the polypeptide. Biological
polypeptides are often several hundred amino acids
long, so few of the possible polypeptides actually occur in
organisms. Linking by peptide (= amide), amino acid
molecules form dipeptide, tripeptide, oligopeptide and
polypeptides. The latter then link with each other, forming
first the peptones, then proteoses. Various proteins of biological
system can be classified into three categories.
1. Simple proteins—These contain only amino acid
Globular proteins—In the molecules of these
proteins, the polypeptide chains are folded into compact
globular or spherical shapes. Hence, the length to breadth
ratio of molecules is usually 1 : 3 or 4 (never more than
1 : 10). That is why, these proteins are noncontractile and
soluble in aqueous systems, forming colloidal solutions
and easily diffusible. All enzymes, many hormones
(insulin, thyroxin, ACTH), the antibodies, albumins and
globulins of blood plasma, globin of haemoglobin,
myoglobin of muscles, histones of nucleoproteins,
glutelins of cereals, prolamines of pulses are examples of
Fibrous proteins—In the molecules of these proteins
the length to breadth ratio is always more than 1 : 10.
Hence, these are insoluble structural proteins that make
the body architecture. The collagen, elastin and reticulin
of connective tissues, tendons, ligaments, cartilage and
bones; the keratin of skin, horns, nails, feathers, hairs; the
fibroin of silk; the actin and myosin of muscles, fibrinogen
of blood plasma, tubulin of microtubules are examples of
fibrous proteins. Collagen is the most abundant protein of
2. Conjugated proteins—These are compounds of
simple proteins conjugated with prosthetic groups.
Phosphoproteins—Compounds of simple proteins
and phosphoric acid. Casein of milk and vitellin of egg-yolk
Nucleoproteins—These form chromatin of chromosomes
in nuclei of cells.
Glycoproteins or Mucoproteins and Proteoglycans—
Their example is the mucin found in connective
tissues, cartilage, saliva etc.
Chromoproteins—Common examples are haemoglobin
and haemocyanin of blood and cytochromes of
3. Derived proteins—Common examples are proteoses
and peptones. These are smaller polypeptide
chains formed as temporary by-products during protein
Proteins cannot, as such diffuse through cell membrane,
only amino acids can diffuse. Of the twenty amino
acids used by humans, only ten are obtained from food.
The other ten are synthesized in the body cells
themselves. Those obtained from food are called
‘essential amino acids’. Food whose proteins yield all
essential amino acids on digestion is called complete
food. Food proteins having all amino acids required for
synthesis of all structural proteins are referred to as
adequate proteins. Contrary to this, food proteins whose
amino acid monomers can be used only for deamination
and energy production are called inadequate proteins.
Human body contains about 65% water. About 70%
of this water is in the protoplasm and rest in the plasma of
blood and lymph, tissue fluid of the intercellular spaces
etc. Water does not yield energy but it is highly vital for
the body. Water is universal solvent.
Minerals (Inorganic salts)
Minerals form about 4% of our body weight. Over a
dozen elements are known to be essential as mineral
salts in the diet. These include sodium (Na), potassium
(K), calcium (Ca), magnesium (Mg), phosphorus (P),
chlorine (Cl), copper (Cu), fluorine (F), manganese (Mn),
cobalt (Co), zinc (Zn), iron (Fe), iodine (I), molybdenum
(Mo) and selenium (Se). Of these, the first six are needed
in relatively large amounts and are called macrominerals;
others are required in very small amounts and are
termed microminerals. The minerals have small molecules
and do not require digestion. They are absorbed
from the alimentary canal into the blood which supplies
them to the tissues. Minerals must be taken as compounds,
if taken as elements, they prove fatal.
Physiological Roles of the Essential Minerals
(Macrominerals) Required in Large Amounts by
Mineral Major Physiological Roles
Calcium (Ca) Component of bone and teeth, essential
for normal blood clotting; needed for
normal muscle, neuron and cell function.
Chlorine (Cl) Principal negative ion in extracellular
fluid; important in acid-base and fluid
balance; needed to produce stomach
Magnesium (Mg) Component of many coenzymes;
needed for normal neuron and muscle
function, as well as carbohydrate and
Potassium (K) Major constituent of bones, blood
plasma; needed for energy metabolism.
Phosphorus (P) Major positive ion in cells; influences
muscle contraction and neuron excitability;
part of DNA, RNA, ATP, energy
Sodium (Na) Principal positive ion in extracellular
fluid; important in fluid balance; essential
for conduction of action potentials,
Sulphur (S) Protein structure; detoxification reactions
and other metabolic activity.
Some Physiological Roles of Trace Minerals
(Microminerals) in Animals
Mineral Major Physiological Roles
Cobalt (Co) Component of vitamin B12; essential for
red blood cell production.
Copper (Cu) Component of many enzymes, essential
for melanin and hemoglobin synthesis;
part of cytochromes.
Fluorine (F) Component of bone and teeth; prevents
Iodine (I) Component of thyroid hormones.
Iron (Fe) Component of hemoglobin, myoglobin,
enzymes and cytochromes.
Manganese (Mn) Activates many enzymes; an enzyme
essential for urea formation and parts of
the Krebs cycle.
Molybdenum (Mo) Constituent of some enzymes.
Selenium (Se) Needed in fat metabolism.
Zinc (Zn) Component of atleast 70 enzymes;
needed for wound healing and fertilization.
The vitamins are organic compounds regularly
required in minute quantities in diet for normal metabolism,
health and growth. Many enzymes of metabolic
reactions are effective only when linked with nonprotein
cofactors and the cofactors are mostly derived from
vitamins. That is why, vitamins are commonly called
‘growth factors’. Diseases caused by their deficiency are
called ‘deficiency diseases’.
The term ‘Vitamin’ was first used by Funk. Knowledge
about vitamins was tremendously accelerated by the work
of Hopkins and Funk.
Vitamins may be water soluble or fat soluble. Most
water soluble vitamins, such as the B vitamins and vitamin
C, are coenzymes needed in metabolism. The fat soluble
vitamins have various functions.
The dietary need for vitamin C and fat soluble
vitamins (A, D, E and K) tends to be limited to the
vertebrates. Even in closely related groups, vitamin
requirements vary. For example, among vertebrates,
humans and guinea pigs require vitamin C but rabbits do
not. Some birds require vitamin A; others do not.
Vitamin Characteristics Functions Sources
Destroyed by heat and oxygen,
especially in alkaline environment
Part of coenzyme needed for
oxidation of carbohydrates and
coenzyme needed in synthesis of
Lean meats, liver, eggs,
whole grain cereals, leafy
green vegetables, legumes
Stable to heat, acids and oxidation;
destroyed by alkalis and light
Part of enzymes and co-enzymes
needed for oxidation of glucose and
fatty acids and for cellular growth
Meats, dairy products, leafy
green vegetables, wholegrain
Stable to heat, acids and alkalis;
converted to niacinamide by cells;
synthesized from tryptophan
Part of coenzymes needed for oxidation
of glucose and synthesis of
proteins, fats and nucleic acids
Liver, lean meats, poultry,
Vitamin B6 Group of three compounds; stable to
heat and acids; destroyed by oxidation,
alkalis and ultraviolet light
Coenzyme needed for synthesis of
proteins and various amino acids, for
conversion of tryptophan to niacin, for
production of antibodies and for
synthesis of nucleic acids
Liver, meat, fish, poultry,
bananas, avocados, beans,
cereals, egg yolk
Pantothenic acid Destroyed by heat, acids and alkalis Part of coenzyme needed for oxidation
of carbohydrates and fats
Meats, fish, whole-grain
cereals, legumes, milk,
Complex, cobalt-containing compound;
stable to heat; inactivated by
light, strong acids and strong alkalis;
absorption regulated by intrinsic factor
from gastric glands; stored in liver
Part of coenzyme needed for synthesis
of nucleic acids and for metabolism
of carbohydrates; plays role in
synthesis of myelin
Liver, meats, poultry, fish,
milk, cheese, eggs
Occurs in several forms; destroyed by
oxidation in acid environment or by
heat in alkaline environment; stored in
liver where it is converted into folinic
Coenzyme needed for metabolism of
certain amino acids and for synthesis
of DNA; promotes production of
normal red blood cells
Liver, leafy green vegetables,
Biotin Stable to heat, acids, and light destroyed
by oxidation and alkalis
Coenzyme needed for metabolism of
amino acids and fatty acids and for
synthesis of nucleic acids
Liver, egg yolk, nuts,
Closely related to monosaccharides;
stable in acids but destroyed by
oxidation, heat, light and alkalis
Needed for production of collagen,
conversion of folacin to folinic acid
and metabolism of certain amino
acids; promotes absorption of iron and
synthesis of hormones from cholesterol
Citrus fruits, citrus juices,
tomatoes, cabbage, potatoes,
leafy green vegetables,
Vitamin Characteristics Functions Sources
Vitamin A Occurs in several forms; synthesized
from carotenes; stored in liver, stable
in heat, acids and alkalis; unstable in
Necessary for synthesis of visual pigments,
mucoproteins, and mucopolysaccharides;
for normal development of bones and teeth;
and for maintenance of epithelial cells
Liver, fish, whole milk, butter,
eggs, leafy green vegetables
and yellow and orange vegetables
Vitamin D A group of sterols; resistant to heat,
oxidation, acids and alkalis; stored in
liver, skin, brain, spleen and bones
Promotes absorption of calcium and phosphorus;
promotes development of teeth and
Produced in skin exposed to
ultraviolet light; in milk, egg yolk,
fish-liver oils, fortified foods
Vitamin E A group of compounds; resistant to
heat and visible light; unstable in
presence of oxygen and ultraviolet
light; stored in muscles and adipose
An antioxidant; prevents oxidation of vitamin
A and polyunsaturated fatty acids; may help
maintain stability of cell membranes
Oils from cereal seeds, salad
oils, margarine, shortenings,
fruits, nuts and vegetables
Vitamin K Occurs in several forms; resistant to
heat but destroyed by acids, alkalis
and light; stored in liver
Needed for synthesis of prothrombin;
needed for blood clotting
Leafy green vegetables, egg
yolk, pork liver, soy oil, tomatoes,
Body requires carbohydrates, proteins and fats in the
approximate proportions of 4 : 1 : 1. Adequate amount of
water, mineral salts and vitamins are also necessary. No
single food can supply all these substances. Hence, a
mixed diet is needed. A diet which can provide materials
for all the metabolic requirements of the body—energy,
growth, replacement and physiological regulation is called
a Balanced diet. Thus the proper quality and quantity of
food is most significant basis of good health, proper
growth, normal activity and vigour and longevity. It has
been scientifically determined that a child of four to six
years approximately requires 1500 k cal, thirteen to
fifteen years child requires 2500 k cal and a youth of
sixteen to eighteen years requires 3000 k cal of energy per
Average Indians have to obtain about 50% of their
requirements of energy from carbohydrates, 35% from
fats and 15% from proteins.
Nutritional Difference between Man and Rabbit
1. Man is omnivorous, while rabbit is herbivorous.
2. Gastric lipase is found in man but its presence in rabbit
3. In man caecum is very small having negligible function,
while caecum helps in digestion of cellulose in rabbits.
4. In rabbit, the intestinal mucous membrane secretes only
secretin hormone to stimulate liver and pancreas. In
man both secretin and CCK are secreted by intestinal
mucous membrane for stimulation of liver and pancreas.
In India many people suffer from faulty or malnutrition
due to unbalanced diet. Hence, these people suffer from
Kwasiorkor—This disease is caused by continued
deficiency of proteins in diet although energy intake may
be adequate. Poor physical and mental growth of children,
reduced vigour and increased sensitivity to infection are
usual symptoms of this disease.
Marasmus—Liver of body stores glycogen to fulfil
body’s requirement of glucose for energy in between
meals. This storage is recouped after every meal. If not
recouped, it may last for perhaps half a day. If meal is
delayed further, the body starts consuming its fat reserve
and proteins. This condition is starvation. Prolonged
starvation causes Marasmus. Marasmus is also a protein
and energy deficiency disease.
Malnutrition also deprives persons of adequate supply
of various vitamins. This leads to various deficiency diseases.
Flatus and foul odour of faeces—Flatus is accumulation
of gases in gastrointestinal tract. Most gases in
stomach are nitrogen and oxygen of air that we swallow
with food. These are generally expelled by belching. In
small intestine, only a small amount of gas is present.
This includes the air passed from stomach or CO2 formed
in duodenum due to reactions between HCl of gastric
juice and bicarbonates of pancreatic juice. In large intestine
the colon bacteria generally ferment and putrefy the
faeces. If faeces contain half digested nutrients, or even if
intestinal absorption is in efficient, a large amount of CO2,
H2, ammonia, methane, hydrogen sulphide and nitrogen
gases are formed due to bacterial action, causing acute
Decarboxylation of certain unabsorbed amino acids,
like tryptophan, by colon bacteria results in the formation
of toxic amines like indole, skatole, mercaptans etc. The
foul odour of flatus and faeces is due to the various gases
of these amines.