09/23/2017

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

termed phototrophs.

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.

Heterotrophic 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

(sparrow, man).

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 ×

k cal)].

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

Carbohydrates 4·1

Lipids 9·3

Proteins 4·4

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

constant temperature.

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.

The Food

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

activities.

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.

Carbohydrates

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

of nature.

Glycogen is the common polysaccharide found in

animals.

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

functions.

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

membranes.

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’.

Lipids

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

nerve fibres.

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

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

etc.

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

monomers.

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

globular proteins.

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

the body.

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

are examples.

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

mitochondria.

3. Derived proteins—Common examples are proteoses

and peptones. These are smaller polypeptide

chains formed as temporary by-products during protein

digestion.

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.

Water

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

Animals

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

HCl.

Magnesium (Mg) Component of many coenzymes;

needed for normal neuron and muscle

function, as well as carbohydrate and

protein metabolism.

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

metabolism.

Sodium (Na) Principal positive ion in extracellular

fluid; important in fluid balance; essential

for conduction of action potentials,

active transport.

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

tooth decay.

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.

Vitamins

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.

Water-Soluble Vitamins

Vitamin Characteristics Functions Sources

Thiamine

(Vitamin B1)

Destroyed by heat and oxygen,

especially in alkaline environment

Part of coenzyme needed for

oxidation of carbohydrates and

coenzyme needed in synthesis of

ribose

Lean meats, liver, eggs,

whole grain cereals, leafy

green vegetables, legumes

Riboflavin

(Vitamin B2)

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

cereals

Niacin

(Nicotinic acid)

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,

peanuts, legumes

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,

peanuts, whole-grain

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,

fruits, vegetables

Cyanocobalamin

(Vitamin B12)

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

Folacin

(Folic acid)

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

acid

Coenzyme needed for metabolism of

certain amino acids and for synthesis

of DNA; promotes production of

normal red blood cells

Liver, leafy green vegetables,

whole-grain cereals,

legumes

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,

legumes, mushrooms

Ascorbic acid

(Vitamin C)

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,

fresh fruits

Fat-Soluble Vitamins

Vitamin Characteristics Functions Sources

Vitamin A Occurs in several forms; synthesized

from carotenes; stored in liver, stable

in heat, acids and alkalis; unstable in

light

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

and fruits

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

bones

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

tissue

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,

cauliflower

Balanced Diet

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

day.

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

is doubtful.

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.

Malnutrition

In India many people suffer from faulty or malnutrition

due to unbalanced diet. Hence, these people suffer from

malnutrition diseases.

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

flatus.

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.

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