Nutrition = Sum of all the interactions between an
organism and the food it consumes. Nutrition is a
basic component of all aspects of health. It is
1. Normal growth and development
2. Tissue maintenance and repair
3. Recovery from illness or surgery
4. Preventing certain diseases
• Nutrients: Substances obtained from food and
used in the body to provide energy and structural
materials and to promote growth, maintenance,
• Essential Nutrients: Nutrients a person must obtain
from food because the body cannot make them for
itself in sufficient quantity to meet physiological
– Ex: Essential amino acids, water
6 classes of nutrients
What happens to food?
• Digestion: process of breaking down large food
molecules so the intestinal tract can absorb them
• Absorption: passage of nutrients through
intestinal walls and into the general circulation of
• Metabolism: all chemical reactions that take
place in the body
The amount of potential energy in food is measured in calories.
A calorie (kilocalorie (kcal) is the amount of energy used to raise the
temperature of 1 kilogram of water from 14 to 15 degrees Celsius
Calculate Energy in a Food
If a food contains 15 grams of carbohydrates, 2
grams of protein, and 5 grams of fat. How many
kcalories is in that food?
15 g of CHO x 4 kcal/g = 60 kcal
2 g of protein x 4 kcal/g = 8 kcal
5 g of fat x 9 kcal/g = 45 kcal
TOTAL = 113 kcal
The body's metabolism, is expressed in a number called the
BASAL METABOLIC RATE (BMR).
• BMR = the number of calories an organism must use in a set
amount of time to maintain life.
The BMR for females is 1300 to 1500 kcal per day.
The BMR for males is 1600 to 1800 kcal per day
• Of course your energy needs vary according the amount of activity taking place
(i.e. the energy demand)
Nutritional Requirements of Diet
The 6 major classes of nutrients
Organic Compounds Inorganic Compounds
• Body’s chief choice of energy.
Although not as concentrated a fuel as fats, sugars are the most important source
of energy for many cells.
Carbohydrates provide the bulk of the calories (4 kcal/gram) in most diets, and
starches provide the bulk of that.
• Found in plant foods and in milk.
Sugars / Monosaccharides
• Three common sugars share the same molecular formula, the
arrangement of atoms differs in each case.
glucose, "blood sugar", the immediate source of energy for cellular
galactose, a sugar in milk (and yogurt)
fructose, a sugar found in honey.
• These are "single" sugars or monosaccharides.
• Two monosaccharides can be linked together to form a
‘Double’ Sugars / Disaccharides
The three common disaccharides are:
sucrose - common table sugar = glucose + fructose
lactose - major sugar in milk = glucose + galactose
maltose - product of starch digestion = glucose + glucose
Starches / Polysaccharides
• Starches are polymers of glucose.
The two types are:
• Plants convert excess glucose into starch for storage.
• White potato, plantain, rice, wheat, and corn are major sources of
starch in the human diet.
Storage of Glucose
• Excess glucose is used to synthesise glycogen
• The structure of glycogen is similar to that of a starch.
• The liver and skeletal muscle are major sites for the storage of
• Glycogen is broken back down into glucose when energy is
• Once the body’s capacity to store glycogen is reached, lipids
are formed by lipogenesis
Oils & Fats / Triglycerides
The two components are:
Fatty acids can be:
Saturated – solid at room temperature
- mostly found in animal fats
Monounsaturated – liquid at room temperature
- found in olive & peanut oils
Polyunsaturated – liquid at room temperature
- found in sunflower, sesame and corn oils
Triglycerides are highly concentrated sources of energy and provide
twice as much energy as carbohydrates or protein
• Phospholipids are an integral part of the cell membrane
• The components are glycerol and fatty acids (as in
triglycerides) with a phosphate group
Both Triglycerides and phospholipids contain Fatty acids,
Some fatty acids must come from the diet:
Essential Fatty Acids
• Essential Fatty Acids
– Body cannot produce, must be consumed
– Both essential fatty acids, linoleic and linolenic
are POLYUNSATURATED fatty acids
• Omega-6 Fatty Acids
– Linoleic Fatty Acid
• Found in vegetable oils, seeds, nuts, and whole-grain foods
• Omega-3 Fatty Acids
– Linolenic Fatty Acid
• Found primarily in fish, but also in soy oils and breast milk
• Steroids share the same molecular formula, the arrangement of atoms
differs in each case.
The different types of steroids include:
Cholesterol – part of the cell membrane & foundation for synthesis of
Sex hormones (oestrogen, Testosterone, etc) – regulate reproductive
Cortisol – a hormone that regulates aspects of metabolism and
Vitamin D – a hormone that regulates calcium storage for growth and
• Cholesterol is necessary for cell membranes
and the production of vitamin D and certain
• Found only in animal foods
• High blood cholesterol levels associated
with increased risk of heart disease
Needed to build, maintain, and repair cells
• Proteins have the most diverse role of Functions include:-
the organic compounds in the body Providing a structural framework
Regulating (integral in endocrine and
• Some have a structural or mechanical Providing the contractile units for body
role, others have physiological roles movement
Providing protection (antibodies etc)
Transport of oxygen (haemoglobin)
Catalysing chemical reactions (enzymes)
Amino Acids bond to form proteins
• Amino acids are the building blocks of proteins.
Bonding of amino acids form combinations known as:-
Dipeptides –2 amino acids
Tripeptide –3 amino acids
Peptides – 4 to 10 amino acids
Polypeptides – 10 to 100 amino acids
Proteins - > 100 amino acids
• Comprised of 20 amino acids
– 10 amino acids must be supplied by diet (“essential amino acids”)
• Complete proteins have all 10 essential amino acids
• Incomplete proteins lack one or more essential amino acids
• Contains all of essential amino acids.
• Include meat, fish, poultry, eggs, milk, and
• Only plant protein that is complete is soy
• Foods that don’t contain all essential amino
acids are incomplete proteins.
• Vitamins do not provide energy or serve as raw materials for synthesis.
• Vitamins have a regulatory function, most as co-enzymes of digestion.
The two categories are:
Fat soluble: A,D,E & K
Water soluble: 8 different B vitamins and vitamin C
(B1, B2, B6, B12, Niacin, Pantothenic Acid, Folic Acid & Biotin and C)
• Provitamins are raw materials needed for the synthesis of certain vitamins
• Antioxidants (Vitamins C and E as well as beta-carotene) protect cells by
reducing or preventing free radical formation
• Serves as a solvent / suspending medium
• Takes place in chemical reactions
• Has a high capacity for heat absorption
• Requires large amounts of heat to evaporate
• Serves as a lubricant
Minimum Water Needed
• Body must excrete a minimum of 500 ml
• More you drink more dilute urine is.
– 1 – 1.5 ml per calorie expended per day, which
is about 2 to 3 liters of water per day for a
person expending 2000 calories per day (8-12
Minerals in the Human Body
• Like vitamins, minerals are essential in regulatory
• Calcium is the most abundant mineral in the body, 99% is
stored in the bones
• NaCl (salt) dissolve to form ions (anions and cations) in
the intracellular and extracellular fluid
• Most of the iron in the body is a component of
haemogloblin and myoglobin
• Zinc is a required cofactor by more than 100 enzymes
• Others take part in many body processes such as nerve
impulse transmission or osmoregularity
Dietary Reference Value (DRV)
• Recommended Nutrient Intakes (RDA and DRI)
The Dietary Reference Intakes (DRIs) are nutrient-based reference
values for use in planning and assessing diets. They are intended to
replace the Recommended Dietary Allowances (RDAs)
• Vegan – Restricts all animal foods
• Lacto-Ovo Vegetarian – Includes milk,
eggs, and cheese
• Many other types
USDA Food Pyramid