Food and Nutrition An Introduction

Why do we eat?

 Satisfy physiological needs  Habit  Social Influences  Psychological Influences  Sensory Appeal

What are our dietary needs?  Meet basic physiological needs  Body function  Maintenance  Temperature regulation  Growth  Physical activity

What should our diet contain?  Essential Dietary components  Lipids (fats)  Carbohydrates  Proteins  Vitamins  Minerals  Desirable  Colour  Flavour

Food Components  Fats, Proteins and Carbohydrates are sometimes called the “Macro components”  They are required in large quantities and form the bulk of your food  Minerals and vitamins are the “Micro components”  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  Lipids are a diverse group of biomolecules which share the property of being insoluble in water  The main classes of lipids are  Oils and fats  Waxes  Phospholipds  Steroids  All except steroids are based on fatty acids.

Oils and Fats  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  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  Monosaccharides  Oligosaccharides  Polysaccharides

Monosaccharides  Monosaccharides are the basic building blocks of carbohydrates  They have the general formula (CH 2 O) n  Two common monosaccharides are glucose and fructose (fruit sugar)  Both have the formula C 6 H 12 O 6  The difference between them is in their structural arrangement

Oligosaccharides  Oligosaccharides are carbohydrates formed from the combination of a few monosaccharide molecules  Of these some disaccharides are common. Common examples include;  Sucrose (glucose + fructose)  Maltose (2 glucose)  Lactose – milk sugar (glucose + galactose)

Polysaccharides  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  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  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  Monosaccharides  Oligosaccharides  Polysaccharides

Monosaccharides  Monosaccharides are the basic building blocks of carbohydrates  They have the general formula (CH 2 O) n  Two common monosaccharides are glucose and fructose (fruit sugar)  Both have the formula C 6 H 12 O 6  The difference between them is in their structural arrangement

Oligosaccharides  Oligosaccharides are carbohydrates formed from the combination of a few monosaccharide molecules  Of these some disaccharides are common. Common examples include;  Sucrose (glucose + fructose)  Maltose (2 glucose)  Lactose – milk sugar (glucose + galactose)

Polysaccharides  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  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  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  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  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  e.g. Vitamin C

Vitamins  Heterogeneous group of substances  They vary greatly in terms of their:  Chemical nature  Function  2 Types  Water-soluble  Fat-soluble

Vitamins  Requirements for vitamins differ during growth and maturity  Additional; quantities required under special circumstance e.g. pregnancy  Other factors  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?  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  Fats  Proteins  Carbohydrates  Minerals  Vitamins  The problem is what is an “appropriate amount”?

 These are the intakes of nutrients which are required to maintain balance in the body  Amounts needed to reverse deficiency  Amounts needed for normal biochemical function  There are three measures  Estimated Average Requirements EAR  Reference Nutrient Intake RNI  Ensure that he needs of nearly all the group (97.5%) are being met  Lower Reference Nutrient Intake LRNI  The amount of a nutrient that is enough for only the small number of people that have low requirements (2.5%) Dietary Reference Values

Level of requirement Percentage of individuals LowHigh ERA Distribution on nutritional requirements in a population LRNI RNI97.5%

 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 ERA’s and diet

Eating a balanced diet  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  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 MAFF produced Eight guidelines for a healthy diet in 1990

 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

Dietary planning – UK food plate 33% 12%15%8%

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  special dietary needs  infants and children under 5  frail elderly