Food and Nutrition

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? • 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 (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 • 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 (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 • 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”?

Dietary Reference Values • 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%)

Distribution on nutritional requirements in a population ERA Percentage of individuals RNI 97.5% LRNI Low Level of requirement High

ERA’s and diet • 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

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

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

Food and Nutrition