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INTRODUCTION TO NUTRITION
• Nutrition may be defined as a science of food
and its relationship with health.
• Nutrients are specific dietary constituents
such as proteins, carbohydrates, fats, vitamins
• Dietics is the practical application of principles
of nutrition: includes planning of meals for the
well and the sick.
• Nutrition is the corner stone of socio
• The concept that health sector alone is
responsible for tackling the nutritional ills of
the society has faded away.
• Broad inter- sectoral and integrated approach
of sectors of development is needed to tackle
today’s nutritional problems.
• Specific nutritional deficiency diseases have
been indentified and technologies developed
to control them.
• Importance of nutrition for immunity, fertility,
maternal and child health and family health
have gained importance.
• Role of dietary factors in the pathogenesis of
non communicable diseases like CHD, diabetes
and cancer have gained importance.
NUTRITIONAL EPIDEMIOLOGY :Epidemiological
assessment of nutritional status of communities,
nutritional and dietary surveys, nutritional
surveillance, nutritional indicators and
nutritional interventions-collectively called as
• Promotion of nutrition is one of the eight
elements of primary health care.
CLASSIFICATION OF FOODS
BY CHEMICAL COMPOSITION:
BY PREDOMINANT FUNCTIONS:
a) Body building foods: eg. Milk ,meat, poultry, pulses
b) Energy giving foods: eg. Cereals, sugar, roots and
tubers, oils and fats
a) Protective foods: eg. Vegetables, fruits, milk
BY NUTRITIVE VALUE:
a) Cereals and millets
d) Nuts and oil seeds
BY NUTRITIVE VALUE:
f) Animal foods
g) Fats and oils
h) Sugar and jaggery
i) Condiments and spices
• Are organic and inorganic complexes contained
• They can be classified into
• They are also called as proximate principles.
• In Indian dietary, they contribute to the total
energy intake in the following proportions:
MICRONUTRIENTS: Vitamins and minerals.
• The word protein by derivation means that it
is of first importance.
• Proteins are complex organic nitrogenous
compounds and composed of carbon,
hydrogen , oxygen , nitrogen and sulphur in
• Proteins constitutes about 20 percent of the
body weight in adults.
• Polypeptides are made by polymerization of
amino acids through peptide bonds
• Big polypeptide chains containing more than
50 amino acids are called proteins.
PRIMARY STRUCTURE: determined by
the sequence of amino acids
SECONDARY STRUCTURE: occurs when
the amino acids are linked by hydrogen
TERTIARY STRUCTURE: formed when alpha
helices and beta pleated sheets are held
together by week interactions
QUARTERNARY STRUCTURE: consists of
more than one polypeptide chains. 13
• Out of the 20 amino acids needed by the
human body, 8 are essential because the body
cannot synthesize them in amounts
corresponding to the needs and hence must
be obtained from dietary sources.
• Essential amino acids are- leucine, isoleucine,
lysine, methionine, phenylalanine, threonine,
valine, tryptophan and Histidine.
• A protein is said to be biologically complete if
it contains all the amino acids in amounts
corresponding to human needs.
• Animal proteins are superior to vegetable
proteins as they are biologically complete.
ASSESSMENT OF PROTEIN
• PROTEIN QUALITY: is assessed by comparison to a
reference protein(egg protein).
• There are two methods of assessment of protein
a)Amino acid score
b)Net protein utilization
• AMINO ACID SCORE:
Amino acid score=mg of amino acid per g of test protein ×100
mg of the same amino acid per gram
of reference protein
Starches - 50-60
Animal foods – 70-80
• NET PROTEIN UTILIZATION(NPU) : It is the product
of digestibility coefficient and biological value divided
NPU= Nitrogen retained in the body × 100
• In calculating protein quality, 1 g of protein is
assumed to be equivalent to 6.25g of nitrogen.
• Total protein requirements varies with the NPU of
dietary proteins.NPU of Indian diet varies between
50 and 80.
• PROTEIN QUANTITY: one way of evaluating food
as a source of protein is to determine what percent
of their energy value is supplied by their protein .
protein energy ratio= energy from protein×100
total energy in diet
It is recommended that protein should account for
approximately 10-12 % of the total energy intake.
SOURCES OF PROTEINS
• Animal sources: Milk , meat, eggs, cheese,
• Vegetable sources: Pulses, cereals, beans, nuts,
oils and seeds.
• In India cereals and pulses are the main
sources of proteins as they are cheap, easily
available and consumed in bulk.
PROTEIN CONTENT OF FOODS
(g. per 100g.. Of food)
Milk 3.2 – 4.3
Meat 18 – 26
Cereals 6 – 13
Pulses 21 – 28
• ICMR expert group suggested an intake of
1gram of protein per kg of body weight for
adult males and females , assuming NPU of 65
for dietary proteins.
GROUP CATEGORY/AGE PROTEIN
MAN Sedentary work
WOMAN Non pregnant 55g/d
Lactating 0-6 m 74g/d
Lactating 6-12 m 68g/d
INFANTS 0-6 months 1.1g/kg/d
6-12 months 1.69g/kg/d
CHILDREN 1-3 years 16.7g/d
4-6 years 20.1g/d
7-9 years 29.6g/d 23
GROUP CATEGORY/AGE PROTEIN
BOYS 10 – 12 Years 39.9 g/d
GIRLS 10 – 12 Years 40.4 g/d
BOYS 13 – 15 Years 54.3 g/d
GIRLS 13 – 15 Years 51.9 g/d
BOYS 16 – 17 Years 61.5 g/d
GIRLS 16 – 17 Years 55.5 g/d
FUNCTIONS OF PROTEINS
A) Body building.
B) Repair and maintenance of body tissues.
C) Maintenance of osmotic pressure.
D) Synthesis of substances like antibodies,
plasma proteins, hemoglobin, enzymes,
hormones and coagulation factors.
PROTEINS CLASSIFIED BY FUNCTION
• CATALYTIC : Enzymes.
• STORAGE: Ovalbumen (in eggs), casein (in
milk), zein (in maize).
• TRANSPORT: Haemoglobin.
• REGULATORY:Hormones (eg. insulin) and
• Proteins are not stored in the human body.
• They are constantly broken down into their
constituent amino acids and then reused for
• The overall turnover in adult man is equivalent
to replacement of 1-2% of the body protein
• The amount of a specific protein in the body is
• Protein deficiency occurs along with energy
deficiency, hence called PROTEIN ENERGY
• The current concept of PEM has two clinical
forms- KWASHIORKOR and MARASMAS.
• They can be prevented by health promotion,
good diet, immunisation, food fortification,
early diagnosis and treatment and
• Park K . Textbook of Preventive and Social
Medicine. 22nd ed. Banarasidas Bhanot
• Vasudevan DM . Text book of biochemistry. 5th
ed. Jaypee brothers medical
• ICMR:recommended dietary allowances
available from url( www.icmr.nic.in/final/RDA-
2010.pdf ) accessed on 22/8/14 at 8:00PM.