Principles of Nutrition

• Protein is a macronutrient, so it is needed by the body in large amounts
• Protein is formed of chains of amino acids
• Essential amino acids cannot me made by the body so they must come from our diets
• Essential amino acids:

  •Histidine

  •Isoleucine

  •Lysine

  •Leucine

  •Methionine

  •Phenylalanine

  •Threonine

  •Tryptophan

  •Valine
• High Biological Value (HBV) proteins contain all the essential amino acids.
• Low Biological Value (LBV) proteins do not contain all the essential amino acids
• Protein complementation is combining two or more proteins in order to get all the essential amino acids
• HBV protein sources:

  •Meat and poultry

  •Vegan meat (Quorn)

  •Soya
• LBV protein sources:

  •Plant sources

  •Most vegan foods
• Protein is needed for growth, repair, and maintenance of cells in the body
• Excess protein is used as energy

  Protein deficiency can cause Kwashiorkor
• Fat is a macronutrient that can be solid or liquid
• Fat is made up of fatty acids and glycerol
• Saturated fats:

  •Solid at room temperature

  •Contains more LDL than HDL cholesterol

  •E.g butter
• Unsaturated fats:

  •Monounsaturated - contains 1 double bond of carbon

  •Polyunsaturated - contains 2+ double bonds of carbon

  •Contains more HDL than LDL cholesterol

  •E.g avocado
• LDL cholesterol - deposits cholesterol into arteries, increasing risk of heart disease
• HDL cholesterol - removes cholesterol from arteries, transporting it to the liver, and reducing the risk of heart disease
• Fats are broken down into lipoproteins:

  •Low-Density Lipoproteins (LDL)

  •High-Density Lipoproteins (HDL)
• Fat functions:

  • Energy source
  • Warmth and insulation (adipose tissue)
  • Fat-soluble vitamins: A,D,E,K
• Trans fats - When a liquid oil goes through hydrogenation, it become solid
• Fat excess:

  • Weight gain
  • High cholesterol
  • Heart disease
  • Some cancers
• Fat deficiency:

  • Affects children's growth
  • Poor vitamin supply
• Carbohydrates:

  • Our main source of energy
  • Comes in sugar, starch, and fibre form
  • Produced mainly from photosynthesis
• Carbohydrates:

  • Our main source of energy
  • Comes in sugar, starch, and fibre form
  • Produced mainly from photosynthesis
• Three types of carbohydrates:

  • Monosaccharides
  • Disaccharides
  • Polysaccharides
• Monosaccharides (sugars):

  • Simplest form of carb structure
  • Glucose, galactose, fructose
• Disaccharides (sugars + starchy):

  • More complex sugars
  • Formed when two monosaccharides join
  • Sucrose - 1 glucose, 1 fructose
  • Maltose - 2 glucose
  • Lactose - 1 glucose, 1 galactose
• Polysaccharides:

  • Many monosaccharides joined together
  • Starch - many glucose
  • Glycogen - digestion of dietary fibre
• Carbohydrate function:

  • Sugars - instant energy
  • Starch - slow release
  • Very filling - helps diets
  • Starchy carbohydrates- healthier form of energy
• Sources of carbohydrates:

  • Starchy - bread, pasta, rice
  • Sugars - fruit, veg, honey, table sugar
• Excess carbohydrates:

  • Converted to fat - obesity
  • Excess sugar - dental decay
  • Risk of Type 2 diabetes
• Carbohydrate deficiency:

  • Body uses protein and fat as energy
• Dietary fibre:

  • Scientific name - Non-Starch Polysaccharide (NSP)
  • Soluble fibre - inhibits absorption of cholesterol
  • Insoluble fibre - passes through body, helps pass faeces
• Function of fibre:

  • Softens food passing through intestines to help it pass through body
• Dietary fibre is found in:

  • Wholemeal bread
  • Wholegrain breakfast cereals
  • Nuts and seeds
• Fibre deficiency:

  • Adults need 18g per day
  • Constipation - faeces hard to pass
  • Diverticular disease - infected pouches in intestines
  • Cancers e.g bowel cancer
• Fat soluble vitamins:

  • Vit A
  • Vit D
  • Vit E
  • Vit K
• Water soluble vitamins:

  • Vit B1
  • Vit B2
  • Vit B3
  • Vit B9
  • Vit B12
  • Vit C
• Vitamin A:

  • Function - maintains skin, iron metabolism, vision, immune function, antioxidant
  • Sources - whole milk, leafy green veg, orange fruits, fortified margarine
  • Excess - liver + bone damage
  • Deficiency - poor immune function, skin, vision
• Vitamin D:

  • Function - calcium and phosphorous absorption
  • Sources - oily fish, meat, eggs, fortified breakfast cereals, sunlight
  • Deficiency - weak bones/teeth, rickets, osteomalacia