Transcript Food and Nutrition - Teesside University

Food and Nutrition
An Introduction
Why do we eat?
Why do we eat?
 Satisfy
physiological needs
 Habit
 Social
Influences
 Psychological Influences
 Sensory Appeal
What are our dietary needs?
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Meet basic physiological needs
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Body function
Maintenance
Temperature regulation
Growth
 Physical activity
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What should our diet contain?
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Essential Dietary components
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Lipids (fats)
Carbohydrates
Proteins
Vitamins
Minerals
Desirable
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Colour
Flavour
Food Components
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Fats, Proteins and Carbohydrates are sometimes
called the “Macro components”
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They are required in large quantities and form the
bulk of your food
Minerals and vitamins are the “Micro
components”
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They are required in small quantities (ranging from a
few grams to a few milligrams/day)
They are nevertheless essential to the proper
functioning of the body
Lipids
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Lipids are a diverse group of biomolecules which
share the property of being insoluble in water
The main classes of lipids are
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Oils and fats
Waxes
Phospholipds
Steroids
All except steroids are based on fatty acids.
Oils and Fats
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Oils and fats are esters of Fatty acids and glycerol
Fatty acids comprise a hydrocarbon chain with a
carboxylic acid group (COOH) at one end.
The hydrocarbon chain length can range from 4 to 22
carbon atoms.
There are two types of fatty acid; saturated and unsaturated
Unsaturated fatty acids have one or more double bonds in
their hydrocarbon chain
Certain unsaturated fatty acids are essential to our diet
Carbohydrates
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Carbohydrates are a major source of energy in
our diet and are used in the body as a store of
available energy
There are three main categories of carbohydrate
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Monosaccharides
Oligosaccharides
Polysaccharides
Monosaccharides
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Monosaccharides are the basic building blocks of
carbohydrates
They have the general formula (CH2O)n
Two common monosaccharides are glucose and
fructose (fruit sugar)
Both have the formula C6H12O6
The difference between them is in their structural
arrangement
Oligosaccharides
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Oligosaccharides are carbohydrates formed from
the combination of a few monosaccharide
molecules
Of these some disaccharides are common.
Common examples include;
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Sucrose (glucose + fructose)
Maltose (2 glucose)
Lactose – milk sugar (glucose + galactose)
Polysaccharides
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Polysaccharides comprise a very large number of
monosaccharide units combined together
Polysaccharides include
 Starch
 Glycogen
 Cellulose
Starch is a energy source of plant origin, glycogen is the
animal equivalent and is our main internal energy source
Cellulose is a structural polymer found in many plants.
Cellulose is a significant component of food, but is not
digestible by humans.
NSP or Dietary Fibre
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NSP; “non-starch polysaccharides” comprises a
range of complex polysaccharides
These are not broken down by the digestive
enzymes in the small intestines, though some are
broken down by bacteria in the large intestine
A diet high in NSP has beneficial effects on health
particularly protecting against a range of chronic
bowel disorders.
Carbohydrates
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Carbohydrates are a major source of energy in
our diet and are used in the body as a store of
available energy
There are three main categories of carbohydrate
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Monosaccharides
Oligosaccharides
Polysaccharides
Monosaccharides
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Monosaccharides are the basic building blocks of
carbohydrates
They have the general formula (CH2O)n
Two common monosaccharides are glucose and
fructose (fruit sugar)
Both have the formula C6H12O6
The difference between them is in their structural
arrangement
Oligosaccharides
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Oligosaccharides are carbohydrates formed from
the combination of a few monosaccharide
molecules
Of these some disaccharides are common.
Common examples include;
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Sucrose (glucose + fructose)
Maltose (2 glucose)
Lactose – milk sugar (glucose + galactose)
Polysaccharides
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Polysaccharides comprise a very large number of
monosaccharide units combined together
Polysaccharides include
 Starch
 Glycogen
 Cellulose
Starch is a energy source of plant origin, glycogen is the
animal equivalent and is our main internal energy source
Cellulose is a structural polymer found in many plants.
Cellulose is a significant component of food, but is not
digestible by humans.
NSP or Dietary Fibre
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NSP; “non-starch polysaccharides” comprises a
range of complex polysaccharides
These are not broken down by the digestive
enzymes in the small intestines, though some are
broken down by bacteria in the large intestine
A diet high in NSP has beneficial effects on health
particularly protecting against a range of chronic
bowel disorders.
Proteins
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Proteins include the largest and most complex
molecules known
They are the main functional component of the
body
Proteins may be divided into two main categories
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Structural, e.g. muscle, connective tissue
Functional, e.g. enzymes
Proteins are built up from amino acids linked
together by peptide bonds
Polypeptides and Proteins
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A chain of amino acids linked via the peptide
bond is called a “Polypeptide”
Proteins are formed from one or more
polypeptides linked together as a consequence of
the properties on the “R” groups on the amino
acids
The structure and properties of proteins is
dependant on the structure which arises as a
result of the folding of the polypeptide chains.
Vitamins
Low molecular weight organic substances
 required in small amounts in the diets of higher
animals for normal growth, maintenance of health,
and reproduction.
 All animals require vitamins
 Not all vitamins are required by all animals
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e.g. Vitamin C
Vitamins
Heterogeneous group of substances
 They vary greatly in terms of their:
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Chemical nature
Function
2 Types
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Water-soluble
Fat-soluble
Vitamins
Requirements for vitamins differ during growth
and maturity
 Additional; quantities required under special
circumstance e.g. pregnancy
 Other factors
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inheritance
microbial flora of the intestine
eating habits
RDA differ between countries
Minerals
 A number
of mineral salts and metals are
essential to proper functioning of the body.
 They perform a variety of functions
including
 Ion
transport
 Essential to certain enzymes
Balanced diets
A Healthy Diet
What nutrients are needed and in
what amounts?
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In practice the majority of people have no idea about the
actual nutrients they require each day.
Nutritionists require more specific information
Nevertheless, balanced diets should contain appropriate
amounts of
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Fats
Proteins
Carbohydrates
Minerals
Vitamins
The problem is what is an “appropriate amount”?
Dietary Reference Values
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These are the intakes of nutrients which are required to
maintain balance in the body
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There are three measures
Estimated Average Requirements EAR
Reference Nutrient Intake RNI
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Amounts needed to reverse deficiency
Amounts needed for normal biochemical function
Ensure that he needs of nearly all the group (97.5%) are being met
Lower Reference Nutrient Intake LRNI
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The amount of a nutrient that is enough for only the small number
of people that have low requirements (2.5%)
Distribution on nutritional
requirements in a population
Percentage of individuals
LRNI
Low
ERA
RNI 97.5%
Level of requirement
High
ERA’s and diet
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The intakes of nutrients which are required to maintain
balance in the body
 Amounts needed to reverse deficiency
 Amounts needed for normal biochemical function
Amount to provide energy requirements
 Basal Metabolic Rates
 Physical Activity Levels
The ERA is an average so
 50% of the population will require more and
 50% will require less
Eating a balanced diet
MAFF produced Eight guidelines for a
healthy diet in 1990
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Enjoy your food
Eat a variety of different
foods
Eat the right amount to be a
healthy weight
Eat plenty of foods rich in
starch
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Don’t eat too much fat
Don’t eat sugary foods too
often
Look after the vitamins and
minerals in your food
if you drink, keep within
sensible limits
Dietary planning
 Meal
selection guides
 Grouping
together foods that provide
(generally) nutrients, and that may be
interchangeable in the diet
 Making a quantitative statement about the
number of servings of foods from each group to
be taken daily
Dietary planning – UK food plate
33%
33%
12%
8%
15%
Alcohol
Men
Regular consumption of between 3 and 4 units a day by
men of all ages will not carry significant health risk.
Women
Regular consumption of between 2 and 3 units a day by
women of all ages will not carry any significant health
risk
Dietary planning
The guide is concerned with proportions of food in
the diet for the average healthy person
 Does not take into account
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special dietary needs
infants and children under 5
frail elderly