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Introduction to nutrition and proteins
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INTRODUCTION TO NUTRITION AND PROTEINS
Santosh KIntern
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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 and minerals.
• Dietics is the practical application of principles of nutrition: includes planning of meals for the well and the sick.
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CHANGING CONCEPTS
• Nutrition is the corner stone of socio economic development.
• 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.
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• 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.
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NUTRITIONAL EPIDEMIOLOGY :Epidemiological assessment of nutritional status of communities, nutritional and dietary surveys, nutritional surveillance, nutritional indicators and nutritional interventions-collectively called as nutritional epidemiology.
• Promotion of nutrition is one of the eight elements of primary health care.
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CLASSIFICATION OF FOODS
BY ORIGIN:a)Animal originb)Vegetable origin
BY CHEMICAL COMPOSITION:a)Proteinsb)Carbohydratesc)Minerals d)Fatse)Vitamins
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BY PREDOMINANT FUNCTIONS:a) Body building foods: eg. Milk ,meat, poultry, pulsesb) Energy giving foods: eg. Cereals, sugar, roots and tubers, oils and fatsc) Protective foods: eg. Vegetables, fruits, milk
BY NUTRITIVE VALUE:d) Cereals and milletse) Pulsesf) Vegetablesg) Nuts and oil seeds
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BY NUTRITIVE VALUE:e) Fruitsf) Animal foodsg) Fats and oilsh) Sugar and jaggeryi) Condiments and spices
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NUTRIENTS• Are organic and inorganic complexes contained in
food.
• They can be classified into 1.Macro nutrients2.Macro nutrients
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MACRONUTRIENTS: • They are also called as proximate principles. • In Indian dietary, they contribute to the total
energy intake in the following proportions: proteins: 7-15% fats: 10-30% carbohydrates 65-80%
MICRONUTRIENTS: Vitamins and minerals.
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PROTEINS
• 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 varying amounts.
• Proteins constitutes about 20 percent of the body weight in adults.
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• Polypeptides are made by polymerization of amino acids through peptide bonds
• Big polypeptide chains containing more than 50 amino acids are called proteins.
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PRIMARY STRUCTURE: determined by the sequence of amino acids
SECONDARY STRUCTURE: occurs when the amino acids are linked by hydrogen bonds.
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.
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• 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.
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• 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.
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ASSESSMENT OF PROTEIN• PROTEIN QUALITY: is assessed by comparison to a
reference protein(egg protein).
• There are two methods of assessment of protein quality:
a)Amino acid score b)Net protein utilization
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• 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
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• NET PROTEIN UTILIZATION(NPU) : It is the product of digestibility coefficient and biological value divided by 100.
NPU= Nitrogen retained in the body × 100 Nitrogen intake
• 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.
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• 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×100total energy in diet
It is recommended that protein should account for approximately 10-12 % of the total energy intake.
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SOURCES OF PROTEINS
• Animal sources: Milk , meat, eggs, cheese, fish
• 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.
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PROTEIN CONTENT OF FOODS
FOOD PROTEIN(g. per 100g.. Of food)
Milk 3.2 – 4.3Meat 18 – 26Egg 13Cereals 6 – 13 Pulses 21 – 28 Soyabean 43.2
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PROTEIN REQUIREMENTS
• 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.
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GROUP CATEGORY/AGE PROTEIN REQUIREMENT
MAN Sedentary workModerate workHeavy work
60g/d
WOMAN Non pregnant 55g/d
pregnant 78g/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
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GROUP CATEGORY/AGE PROTEIN REQUIREMENT
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
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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.
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PROTEINS CLASSIFIED BY FUNCTION
• CATALYTIC : Enzymes.
• STORAGE: Ovalbumen (in eggs), casein (in milk), zein (in maize).
• TRANSPORT: Haemoglobin.
• REGULATORY:Hormones (eg. insulin) and neurotransmitters.
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• CONTRACTILE: Actin, myosin, dynein (in microtubules)
• PROTECTIVE: Immunoglobulin, fibrinogen, blood clotting factors
• STRUCTURAL: Cell membrane proteins, keratin (hair), collagen .
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PROTEIN METABOLISM• Proteins are not stored in the human body.• They are constantly broken down into their
constituent amino acids and then reused for protein synthesis.
• The overall turnover in adult man is equivalent to replacement of 1-2% of the body protein each day.
• The amount of a specific protein in the body is kept constant.
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DEFICIENCY DISEASES
• Protein deficiency occurs along with energy deficiency, hence called PROTEIN ENERGY MALNUTRITION.
• 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 rehabilitation.
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REFERENCES
• Park K . Textbook of Preventive and Social Medicine. 22nd ed. Banarasidas Bhanot publishers;2013: 563-565,588-589,592
• Vasudevan DM . Text book of biochemistry. 5th ed. Jaypee brothers medical publishers;2009:18,21,27,31- 32
• ICMR:recommended dietary allowances available from url( www.icmr.nic.in/final/RDA-2010.pdf ) accessed on 22/8/14 at 8:00PM.
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THANK YOU