Download NUTRIENTS

NUTRIENTS
OBJECTIVES
1.
2.
3.
Define nutrients
Classify nutrients
Comprehend structure and functions of nutrients
NUTRIENTS

Nutrients have been defined as “chemical substances found in
food that cannot be synthesized at all or in sufficient
amounts in the body, and are necessary for life, growth and
tissue repair”.
or

“Nutrient “or “food factor” are organic and inorganic
complexes contained in food, which are responsible for the
functions of foods and protect the body from disorders”.
NUTRIENTS

1.
2.
3.
4.
5.
6.
Nutrients include;
Proteins
Carbohydrates
Lipids
Vitamins
Minerals
Water
CLASSIFICATION OF NUTRIENTS

Classification on Basis of Requirement:
1.
Macronutrients:
•
•
•
•
Carbohydrates (65 – 80%)
Fats and oils (10-30%)
Proteins (7-15%)
These ore often called “proximate principles” because they
form the main bulk of food.
CLASSIFICATION OF NUTRIENTS
2. Micronutrients:
•
Minerals
Vitamins
•
Require in small amounts i.e milligram to micrgram
•
NUTRIENTS
CARBOHYDRATES (CARBS)

Carbohydrates (from 'hydrates of carbon') or saccharides
(Greek σάκχαρον, sákcharon, meaning "sugar") are the most
abundant of the four major classes of biomolecules.

Carbohydrates provide the largest single source of energy in
the diet; providing 4 kcal per gram and satisfy our instinctual
desire for sweetness.

Carbohydrates are substances having the empirical formula
Cx(H2O)y , e.g C6(H2O)6 = glucose (Fig. 2.1).
Fig. 2.1 :The structure of glucose, fructose & sucrose
CLASSIFICATION OF CARBOHYDRATES

The basic building block of carbohydrates
monosaccharide, often glucose itself.
is
a

Carbohydrates are classified depending on the number of
monomer (sugar) units they contain.
CLASSIFICATION OF CARBOHYDERATES
CARBOHYDERATES
SIMPLE
CARBOHYDERATES
COMPLEX
CARBOHYDERATES
• MONOSACCHARIDE
(Glucose, Fructose, Galactose)
• OLIGOSACCHARIDE
• DISACCHARIDE
(Sucrose, Lactose, Maltose)
• POLYSACCHARIDE
(Starch, glycogen, dietary fibers)
(Human milk oligosaccharide)
SIMPLE CARBOHYDRATES:
MONOSACCHARIDES

The simplest carbohydrates are the monosaccharides, or
simple sugars.

The three most common monosaccharides are;
i.
ii.
iii.
Glucose
Fructose
Galactose
SIMPLE CARBOHYDRATES:
DISACCHARIDES

Disaccharides are double sugars
monosaccharide units linked together.

Examples of disaccharides are:
1.
2.
3.
Sucrose (Glucose + Fructose)
Lactose (Glucose + Galactose)
Maltose (Glucose+ Glucose)
which
contain
two
SOURCES OF CARBOHYDRATES
COMPLEX CARBOHYDERATES:
POLYSACCHARIDES

Oligosaccharides contain between 3 and 11 monosaccharide
residues.

Polysaccharides are
monosaccharides.

The polysaccharides tend to be insoluble in water, and only
some can be used by human beings to produce energy.
those
with
longer
chains
of
COMPLEX CARBOHYDERATES:
POLYSACCHARIDES

1.
2.
Polysaccharides are classified as:
Starch Polysaccharide
Non-starch Polysaccharide
STARCH POLYSACCHARIDES

Glycogen is made in the human body and is
sometimes known as “animal starch”.

Surplus monosaccharides that are not used to produce
energy are converted to glycogen which is stored in
liver and skeletal muscles for later use as an energy
source.

The body’s glycogen stores are relatively small (250–
500 g in a 50–70 kg adult human); Most of the stored
glycogen is released and oxidized within 12 hrs.
STARCH POLYSACCHARIDES

Starch is an important source of energy for humans.

Starch molecules in plants occur as granules in the form of
amylose and amylopectin.

Starch is liberated during cooking when the starch granules
rupture because of heating.

As much as 10–20% of dietary starch in individual foods and
mixed meals is not digested to glucose; It is referred to as
‘Resistant Starch’.
STARCH

1.
2.
3.

Foods containing large amounts of starch include;
Cereals (e.g. wheat, rice, maize),
Root vegetables (e.g. potato) and
Legumes (e.g. kidney beans, baked beans)
There is little starch in most fruits and vegetables, apart from
bananas, roots and tubers.
NON-STARCH POLYSACCHRIDE

Some plant polysaccharides
in foods are resistant to
hydrolysis by human digestive enzymes and are referred to as.
“Non-starch Polysaccharide”. They form the main part of
dietary fiber.

Cellulose, hemicellulose, lignin, pectin and gums are mainly
non-starch polysaccharide, present in plants.
SOURCES
FUNCTIONS OF CARBOHYDERATES

Carbohydrate provides 4 KCal per gram. The body can obtain
all its energy from protein and fats.

However, the neurons generally cannot burn fat and need
glucose for energy;

Carbohydrates and their derivatives play major roles in the
working process of the immune system, fertilization, blood
clotting, and development.
FUNCTIONS OF CARBOHYDERATES

Diets high in carbohydrate are usually associated with lower
prevalence of obesity, heart disease, non-insulin-dependent
diabetes.

Carbohydrates (dietary fiber) helps in digestion and in
preventing constipation, mainly by absorbing water, and
increasing the bulk of the diet & stool.

Because it facilitates the rapid passage of materials through the
intestine, fibre may be a factor in the control of diverticulitis,
appendicitis, haemorrhoids.
BENEFICIAL EFFECTS OF CARBOHYDRATES

The bulk in high-fibre diets may contribute a feeling of
fullness or satiety which may lead to less consumption of
energy, and this may help reduce the likelihood of obesity.

High intakes of dietary fibers may also reduce the risk of large
bowel cancer. Fibre may bind the carcinogenic substances and
speed their transit through the gut.

Fiber also increases the amount of water in the faeces, thereby
diluting the effect of any carcinogens.
RECOMMENDED INTAKE OF
CARBOHYDRATE

The Food and Agriculture Organization and World Health
Organization jointly recommend that 55-75% of total energy
intake should be from carbohydrates, but only 10% directly
from sugars (simple carbohydrates).

Most Pakistani diet, contains excessive amount of
carbohydrate, providing as much as 90% of total energy
intake.
DIETARY PROTEINS
DIETARY PROTEINS

The word protein means “that which is of first importance”.

Proteins are complex organic nitrogenous compounds containing
nitrogen and often sulphur in addition to carbon, hydrogen,
oxygen.

For an adult man who weighs 70 kg, about 16% of body weight
is made by protein (i.e. about 11 kg); with 43% in muscles, 16%
in blood and 15% in skin.
AMINO ACIDS

Amino acids are the building blocks of protein. The amino
acids are linked in chains through peptide bonds.

There are 20 amino acids required for protein synthesis and are
divided in two groups:
1.
Essential Amino Acids (cannot be synthesized by the body)
Non-essential Amino Acids (can be synthesized by the body)
2.
AMINO ACIDS

There are 9 EAA including;

Leucine,
Isoleucine,
Lysine,
Methonine,
Threonine,
Valine,
Tryptophane,
Phenylalanine and
Histidine.








FUNCTIONS OF PROTEIN

i.
ii.
iii.
iv.
v.
vi.
Functions of proteins include:
Growth and development of the body;
Maintenance, repair & replacement of damaged tissues;
Part of metabolic & digestive enzymes and hormones;
Maintenance of osmotic pressure;
Protein are essential for immunity;
Protein can also supply energy (4 kcal per gram)
CLASSIFICATION OF DIETARY PROTEINS
1.
2.
“Biologically Complete Protein” contains all the amino acids
needed to build new proteins. Animal sources of protein tend
to be complete.
“Biologically Incomplete Proteins” lack one or more amino
acids that the body can't make at all or create by modifying
another amino acid.

These usually come from fruits, vegetables, grains, and nuts.

Adults need a minimum of 0.8 to 1 gram of protein per
kilogram of body weight per day.
SOURCES OF PROTEIN

1.

2.
Humans obtain protein from two main dietary sources:
Animal Sources, also called “First Class Proteins” as they
are biologically of higher value.
Animal Sources include milk, eggs, meat, cheese, fish,
poultry, butter, yougart.
Plant sources are pulses, cereals, beans, nuts, oil seed.
SOURCES OF PROTEIN
FATS AND OILS: DIETARY FATS
LIPIDS

Lipids are a group of compounds that contain carbon,
hydrogen and oxygen like carbohydrates. Lipids dissolve in
organic solvents such as petrol or chloroform, but are usually
insoluble in water.

The word "oil" is used to refer to those lipids that are liquid at
room temperature such as groundnut or cottonseed oil , while
those that are solid are called “fats” such as butter.

Fats which become liquid at body temperature, like ghee and
butter are digested and absorbed more readily than beef fat,
which has a higher melting point.
CLASSIFICATION OF LIPIDS

Fats (also referred to as lipids) in the body are divided into two
groups:
1.
Storage fat - provides a reserve storehouse of fuel for the
body
2.
Structural fats - are part of the essential structure of the cells,
occurring in cell membranes, mitochondria and intracellular
organelles.
CLASSIFICATION OF FATS

•
•
•
Fats are classified as;
Simple Lipids – Triglycerides
Compound Lipids – Phospholipids
Derived Lipids – Cholestrol

Triglycerides make up about 95% of dietary lipids.

Lipids yield fatty acids and glycerol on hydrolysis.
Fig 3.1: Formation of a Triglyceride Molecule
FATTY ACIDS

Fatty acid consist of a chain of carbon atoms with hydrogens
attached, a methyl group at one end and a carboxylic acid
group at the other (Fig. 3.2).

Fatty acids are classified as;
1.
2.

Essential Fatty Acids (Can’t be synthesized by body)
Non Essential Fatty Acids ((Can be synthesized by body)
The most important EFA is Linoleic Acid which serve as the
basis for the production of other essential fatty acids (e.g
linolenic acid & Arachidonic acid).
Fig. 3.2: Structure of A Fatty Acid
CLASSIFICATION OF LIPIDS

Lipids may be classified as Saturated or Unsaturated
depending on the detailed structure of the fatty acids involved.

Saturated fatty acids are those in which carbon–carbon bonds
are fully saturated with hydrogen atoms (i.e. 4 hydrogens per
carbon–carbon bond).

Unsaturated fatty acids are formed when 2 hydrogens are
absent, the carbons form double bonds with each other.
CLASSIFICATION OF LIPIDS

i.
ii.
Unsaturated fats may be further classified as on the basis of
number of double bonds:
Monounsaturated (one double-bond)
Polyunsaturated (two or more double-bonds)
FUNCTIONS OF LIPIDS

In addition to enhancing the flavour and palatability of food,
lipids make an important contribution to adequate nutrition.

Lipids are required for a range of metabolic and physiological
processes and to maintain the structural and functional
integrity of all cell membranes.

They are major sources of energy; – 1 gram of fat gives 9 kcal
of energy.

Lipids are also the only form in which the body can store
energy for a prolonged period of time.
FUNCTIONS OF LIPIDS

These stored lipids in adipose tissue also serve to provide
insulation, help to control body temperature, and afford some
physical protection to internal organs.

Fats in the body support viscera such as heart, kidney, and
intestine.

Lipids are also required for the absorption of fat soluble
vitamins.
RECOMMENDED LIPID INTAKE

For the adults, dietary fat should provide at least 15 - 20% total
energy.

At least 50% of fat intake should consists of vegetable oils rich
in essential fatty acids.

Saturated fat intake should be less than 7-10 % of total daily
caloric intake.

For infants and young children, dietary fat are equally
important. At least until the age of two years, a child’s diet
should contain about 40% of energy from fat.
SOURCES OF LIPIDS

Naturally occurring dietary lipids are derived from a wide
variety of animal and plant sources including
1.
Animal sources: Animal adipose tissue (the visible fat on
meat); Eggs; fish oil; Milk and products derived from milk fat
(cream, butter, cheese, and yoghurt);
Plant Sources: Vegetable seeds and nuts and plant leaves.
2.

The saturated fatty acids are mostly found in animal fats and
unsaturated fatty acids in vegetable oil.
SOURCES OF FATS
HEALTH EFFECTS OF DIETARY LIPIDS

1.
2.
3.
Among adults the major health issues concerning intake of fat
centre around the role of excessive dietary fat in;
Coronary heart disease,
Obesity and
Certain cancers.
WATER

Water constitutes 60-70% of body weight.

Water serves as the body’s transportation system; distributing
nutrients and essential elements throughout the body.

Water also works as the transport for body waste removal.

Water regulates body temperature.

Daily recommendation for water intake varies in individuals,
related to climate, physical activity, age, body size, and state of
health.
MICRONUTRIENTS:
MINERALS AND VITAMINS
VITAMINS

Vitamins are a class of organic compounds categorized as
essential nutrients. Vitamins belong to the category of
Protective foods.

Body needs vitamins in very small amounts, but they are
absolutely essential for normal metabolism.

Most of the vitamins are discovered during the period of 1890
-1940.
CLASSIFICATION OF VITAMINS

1.
2.
Vitamins are classified as:
Water soluble vitamins
Fat-soluble vitamins
WATER-SOLUBLE VITAMINS

Water-soluble vitamins are easily absorbed by human body.

Water-soluble vitamins dissolve easily in water, and in
general, are readily excreted from the body, to the degree that
urinary output is a strong predictor of vitamin consumption

Body doesn’t store large amounts of water-soluble vitamins,
and they need to be taken regularly.

Many types of water-soluble vitamins are synthesized by
bacteria.
WATER-SOLUBLE VITAMINS

i.
ii.
iii.
Water-soluble vitamins include:
B complex vitamins (Thiamine, Riboflavin, Niacin,
Pantothenic Acid, Vitamin B-6, Vitamin B-12, Biotin)
Folic Acid
Vitamin C
FAT-SOLUBLE VITAMINS

Fat-soluble vitamins are absorbed through the intestinal tract
with the help of lipids (fats).

Fat-soluble Vitamins require bile acids to absorb fat-soluble
vitamins.

Once these vitamins are absorbed, body stores them in body
fat, and used when body need them.

Because they are more likely to accumulate in the body, they
are more likely to lead to hypervitaminosis than are watersoluble vitamins.

Fat-soluble vitamins include vitamins A, D, E, K.
SOURCES OF VITAMINS

Vitamins are produced mainly in plants.

Vitamins can be obtained directly from the foods and
indirectly by animal food to man.

Human body can also make vitamins in the intestine by so
called “friendly bacteria”.
MINERALS

Minerals are organic and inorganic substances categorized as
essential nutrients. Minerals belong to the category of
Protective foods.

Body needs minerals in very small amounts, but they are
absolutely essential for normal metabolism.

Minerals make up about 4-5% of the body weight.

Minerals are required for growth, repair and regulation of vital
body functions.
CLASSIFICATION OF MINERALS

1.
2.
There are two kinds of minerals:
Major or Macrominerals
Trace minerals or elements
CLASSIFICATION OF MINERALS

Major or Macrominerals are minerals your body needs in
larger amounts.

They include calcium, phosphorus, magnesium, sodium,
potassium, chloride and sulfur.

Trace minerals are required in small amounts.

These include iron, manganese, copper, iodine, zinc, cobalt,
fluoride and selenium.
FUNCTIONS OF MINERALS

Micronutrients perform structural and catalytic role including
activation of enzymes and hormones.

They also regulate metabolic processes and participate in
antioxidant enzyme system.

Body needs a small but continuous intake of the minerals to
maintain its structure and functions.

If metabolic needs of these salts are not met, deficiency occurs
causing symptoms which vary with the mineral element
involve.
SOURCES OF VITAMINS AND MINERALS
CONCLUSION
TEXT BOOKS

Textbook of Community Medicine. By Prof. H.A
Siddique.(2nd Edition).

Parks Textbook of Preventive and Social Medicine. K.Park.
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