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Why do we eat?Why do we eat?
Satisfy physiological needsSatisfy physiological needs HabitHabit Social InfluencesSocial Influences Psychological InfluencesPsychological Influences Sensory AppealSensory Appeal
What are our dietary What are our dietary needs?needs?
Meet basic physiological needsMeet basic physiological needs Body functionBody function Maintenance Maintenance Temperature regulationTemperature regulation
GrowthGrowth Physical activityPhysical activity
What should our diet What should our diet contain?contain?
Essential Dietary componentsEssential Dietary components Lipids (fats)Lipids (fats) CarbohydratesCarbohydrates ProteinsProteins VitaminsVitamins MineralsMinerals
DesirableDesirable ColourColour FlavourFlavour
Food ComponentsFood Components
Fats, Proteins and Carbohydrates are sometimes Fats, Proteins and Carbohydrates are sometimes called the “Macro components”called the “Macro components”
They are required in large quantities and form the They are required in large quantities and form the bulk of your foodbulk of your food
Minerals and vitamins are the “Micro Minerals and vitamins are the “Micro components”components”
They are required in small quantities (ranging from a They are required in small quantities (ranging from a few grams to a few milligrams/day)few grams to a few milligrams/day)
They are nevertheless essential to the proper They are nevertheless essential to the proper functioning of the bodyfunctioning of the body
LipidsLipids
Lipids are a diverse group of biomolecules which Lipids are a diverse group of biomolecules which share the property of being insoluble in watershare the property of being insoluble in water
The main classes of lipids areThe main classes of lipids are Oils and fatsOils and fats WaxesWaxes PhospholipdsPhospholipds SteroidsSteroids
All except steroids are based on fatty acids.All except steroids are based on fatty acids.
Oils and FatsOils and Fats
Oils and fats are esters of Fatty acids and glycerolOils and fats are esters of Fatty acids and glycerol Fatty acids comprise a hydrocarbon chain with a Fatty acids comprise a hydrocarbon chain with a
carboxylic acid group (COOH) at one end.carboxylic acid group (COOH) at one end. The hydrocarbon chain length can range from 4 to 22 The hydrocarbon chain length can range from 4 to 22
carbon atoms.carbon atoms. There are two types of fatty acid; saturated and unsaturatedThere are two types of fatty acid; saturated and unsaturated Unsaturated fatty acids have one or more double bonds in Unsaturated fatty acids have one or more double bonds in
their hydrocarbon chaintheir hydrocarbon chain Certain unsaturated fatty acids are essential to our dietCertain unsaturated fatty acids are essential to our diet
CarbohydratesCarbohydrates
Carbohydrates are a major source of energy in Carbohydrates are a major source of energy in our diet and are used in the body as a store of our diet and are used in the body as a store of available energyavailable energy
There are three main categories of carbohydrateThere are three main categories of carbohydrate MonosaccharidesMonosaccharides OligosaccharidesOligosaccharides PolysaccharidesPolysaccharides
MonosaccharidesMonosaccharides
Monosaccharides are the basic building blocks of Monosaccharides are the basic building blocks of carbohydratescarbohydrates
They have the general formula (CHThey have the general formula (CH22O)O)nn
Two common monosaccharides are glucose and Two common monosaccharides are glucose and fructose (fruit sugar)fructose (fruit sugar)
Both have the formula CBoth have the formula C66HH1212OO66
The difference between them is in their structural The difference between them is in their structural arrangementarrangement
OligosaccharidesOligosaccharides
Oligosaccharides are carbohydrates formed from Oligosaccharides are carbohydrates formed from the combination of a few monosaccharide the combination of a few monosaccharide moleculesmolecules
Of these some disaccharides are common. Of these some disaccharides are common. Common examples include;Common examples include;
Sucrose (glucose + fructose)Sucrose (glucose + fructose) Maltose (2 glucose)Maltose (2 glucose) Lactose – milk sugar (glucose + galactose)Lactose – milk sugar (glucose + galactose)
PolysaccharidesPolysaccharides
Polysaccharides comprise a very large number of Polysaccharides comprise a very large number of monosaccharide units combined togethermonosaccharide units combined together
Polysaccharides includePolysaccharides include StarchStarch GlycogenGlycogen CelluloseCellulose
Starch is a energy source of plant origin, glycogen is the Starch is a energy source of plant origin, glycogen is the animal equivalent and is our main internal energy sourceanimal equivalent and is our main internal energy source
Cellulose is a structural polymer found in many plants. Cellulose is a structural polymer found in many plants. Cellulose is a significant component of food, but is not Cellulose is a significant component of food, but is not
digestible by humans.digestible by humans.
NSP or Dietary FibreNSP or Dietary Fibre
NSP; “non-starch polysaccharides” comprises a NSP; “non-starch polysaccharides” comprises a range of complex polysaccharides range of complex polysaccharides
These are not broken down by the digestive These are not broken down by the digestive enzymes in the small intestines, though some are enzymes in the small intestines, though some are broken down by bacteria in the large intestinebroken down by bacteria in the large intestine
A diet high in NSP has beneficial effects on A diet high in NSP has beneficial effects on health particularly protecting against a range of health particularly protecting against a range of chronic bowel disorders. chronic bowel disorders.
CarbohydratesCarbohydrates
Carbohydrates are a major source of energy in Carbohydrates are a major source of energy in our diet and are used in the body as a store of our diet and are used in the body as a store of available energyavailable energy
There are three main categories of carbohydrateThere are three main categories of carbohydrate MonosaccharidesMonosaccharides OligosaccharidesOligosaccharides PolysaccharidesPolysaccharides
MonosaccharidesMonosaccharides
Monosaccharides are the basic building blocks of Monosaccharides are the basic building blocks of carbohydratescarbohydrates
They have the general formula (CHThey have the general formula (CH22O)O)nn
Two common monosaccharides are glucose and Two common monosaccharides are glucose and fructose (fruit sugar)fructose (fruit sugar)
Both have the formula CBoth have the formula C66HH1212OO66
The difference between them is in their structural The difference between them is in their structural arrangementarrangement
OligosaccharidesOligosaccharides
Oligosaccharides are carbohydrates formed from Oligosaccharides are carbohydrates formed from the combination of a few monosaccharide the combination of a few monosaccharide moleculesmolecules
Of these some disaccharides are common. Of these some disaccharides are common. Common examples include;Common examples include;
Sucrose (glucose + fructose)Sucrose (glucose + fructose) Maltose (2 glucose)Maltose (2 glucose) Lactose – milk sugar (glucose + galactose)Lactose – milk sugar (glucose + galactose)
PolysaccharidesPolysaccharides
Polysaccharides comprise a very large number of Polysaccharides comprise a very large number of monosaccharide units combined togethermonosaccharide units combined together
Polysaccharides includePolysaccharides include StarchStarch GlycogenGlycogen CelluloseCellulose
Starch is a energy source of plant origin, glycogen is the Starch is a energy source of plant origin, glycogen is the animal equivalent and is our main internal energy sourceanimal equivalent and is our main internal energy source
Cellulose is a structural polymer found in many plants. Cellulose is a structural polymer found in many plants. Cellulose is a significant component of food, but is not Cellulose is a significant component of food, but is not
digestible by humans.digestible by humans.
NSP or Dietary FibreNSP or Dietary Fibre
NSP; “non-starch polysaccharides” comprises a NSP; “non-starch polysaccharides” comprises a range of complex polysaccharides range of complex polysaccharides
These are not broken down by the digestive These are not broken down by the digestive enzymes in the small intestines, though some are enzymes in the small intestines, though some are broken down by bacteria in the large intestinebroken down by bacteria in the large intestine
A diet high in NSP has beneficial effects on A diet high in NSP has beneficial effects on health particularly protecting against a range of health particularly protecting against a range of chronic bowel disorders. chronic bowel disorders.
ProteinsProteins
Proteins include the largest and most complex Proteins include the largest and most complex molecules knownmolecules known
They are the main functional component of the They are the main functional component of the bodybody
Proteins may be divided into two main categoriesProteins may be divided into two main categories Structural, e.g. muscle, connective tissueStructural, e.g. muscle, connective tissue Functional, e.g. enzymesFunctional, e.g. enzymes
Proteins are built up from amino acids linked Proteins are built up from amino acids linked together by peptide bondstogether by peptide bonds
Polypeptides and Polypeptides and ProteinsProteins
A chain of amino acids linked via the peptide A chain of amino acids linked via the peptide bond is called a “Polypeptide”bond is called a “Polypeptide”
Proteins are formed from one or more Proteins are formed from one or more polypeptides linked together as a consequence of polypeptides linked together as a consequence of the properties on the “R” groups on the amino the properties on the “R” groups on the amino acidsacids
The structure and properties of proteins is The structure and properties of proteins is dependant on the structure which arises as a dependant on the structure which arises as a result of the folding of the polypeptide chains.result of the folding of the polypeptide chains.
VitaminsVitamins
Low molecular weight organic substancesLow molecular weight organic substances required in small amounts in the diets of higher required in small amounts in the diets of higher
animals for normal growth, maintenance of health, animals for normal growth, maintenance of health, and reproduction.and reproduction.
All animals require vitaminsAll animals require vitamins Not all vitamins are required by all animalsNot all vitamins are required by all animals
e.g. Vitamin Ce.g. Vitamin C
VitaminsVitamins
Heterogeneous group of substancesHeterogeneous group of substances They vary greatly in terms of their:They vary greatly in terms of their:
Chemical nature Chemical nature FunctionFunction
2 Types2 Types Water-solubleWater-soluble Fat-solubleFat-soluble
VitaminsVitamins
Requirements for vitamins differ during growth Requirements for vitamins differ during growth and maturityand maturity
Additional; quantities required under special Additional; quantities required under special circumstance e.g. pregnancy circumstance e.g. pregnancy
Other factorsOther factors inheritanceinheritance microbial flora of the intestinemicrobial flora of the intestine eating habitseating habits
RDA differ between countriesRDA differ between countries
MineralsMinerals
A number of mineral salts and metals are A number of mineral salts and metals are essential to proper functioning of the body.essential to proper functioning of the body.
They perform a variety of functions They perform a variety of functions includingincluding Ion transportIon transport Essential to certain enzymesEssential to certain enzymes
What nutrients are needed What nutrients are needed and in what amounts?and in what amounts?
In practice the majority of people have no idea about the In practice the majority of people have no idea about the actual nutrients they require each day.actual nutrients they require each day.
Nutritionists require more specific informationNutritionists require more specific information Nevertheless, balanced diets should contain appropriate Nevertheless, balanced diets should contain appropriate
amounts of amounts of FatsFats ProteinsProteins CarbohydratesCarbohydrates MineralsMinerals VitaminsVitamins
The problem is what is an “appropriate amount”?The problem is what is an “appropriate amount”?
These are the intakes of nutrients which are required to These are the intakes of nutrients which are required to maintain balance in the bodymaintain balance in the body Amounts needed to reverse deficiencyAmounts needed to reverse deficiency Amounts needed for normal biochemical functionAmounts needed for normal biochemical function
There are three measuresThere are three measures Estimated Average Requirements EAREstimated Average Requirements EAR Reference Nutrient Intake RNI Reference Nutrient Intake RNI
Ensure that he needs of nearly all the group (97.5%) are being metEnsure that he needs of nearly all the group (97.5%) are being met
Lower Reference Nutrient Intake LRNILower Reference Nutrient Intake LRNI The amount of a nutrient that is enough for only the small number The amount of a nutrient that is enough for only the small number
of people that have low requirements (2.5%)of people that have low requirements (2.5%)
Dietary Reference Dietary Reference ValuesValues
Level of requirement
Perce
nta
ge o
f ind
ivid
uals Low High
ERA
Distribution on nutritional Distribution on nutritional requirements in a requirements in a
populationpopulation
LRNI RNI 97.5%
The intakes of nutrients which are required to maintain The intakes of nutrients which are required to maintain balance in the bodybalance in the body Amounts needed to reverse deficiencyAmounts needed to reverse deficiency Amounts needed for normal biochemical functionAmounts needed for normal biochemical function
Amount to provide energy requirementsAmount to provide energy requirements Basal Metabolic RatesBasal Metabolic Rates Physical Activity LevelsPhysical Activity Levels
The ERA is an average so The ERA is an average so 50% of the population will require more and50% of the population will require more and 50% will require less50% will require less
ERA’s and dietERA’s and diet
Eating a balanced dietEating a balanced diet
Enjoy your foodEnjoy your food Eat a variety of different Eat a variety of different
foodsfoods Eat the right amount to be a Eat the right amount to be a
healthy weighthealthy weight Eat plenty of foods rich in Eat plenty of foods rich in
starchstarch
Don’t eat too much fatDon’t eat too much fat Don’t eat sugary foods too Don’t eat sugary foods too
oftenoften Look after the vitamins and Look after the vitamins and
minerals in your foodminerals in your food if you drink, keep within if you drink, keep within
sensible limitssensible limits
MAFF produced Eight guidelines for a MAFF produced Eight guidelines for a healthy diet in 1990healthy diet in 1990
Meal selection guidesMeal selection guides Grouping together foods that provide Grouping together foods that provide
(generally) nutrients, and that may be (generally) nutrients, and that may be interchangeable in the dietinterchangeable in the diet
Making a quantitative statement about the Making a quantitative statement about the number of servings of foods from each group to number of servings of foods from each group to be taken dailybe taken daily
Dietary planningDietary planning
AlcoholAlcohol
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 planningDietary planning
The guide is concerned with proportions of food The guide is concerned with proportions of food in the diet for the average healthy personin the diet for the average healthy person
Does not take into accountDoes not take into account special dietary needsspecial dietary needs infants and children under 5infants and children under 5 frail elderlyfrail elderly
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