Macronutrients

Nutrients

  • Nutrients are substances found in food and water.
  • Used for:
    • Energy
    • Growth and repair
    • Chemical reactions

Macronutrients

  • Macronutrients are essential nutrients required by the body in the greatest amounts.
    • Carbohydrates
    • Lipids (fats)
    • Protein

Carbohydrates

  • Easy source of energy – carbohydrates are ultimately broken down into glucose in the digestive tract.
  • 17kJ/gram
  • Carbohydrate is necessary to avoid ketosis.
  • Source of fibre.
  • Sugar is used to form DNA and RNA, and is the foundation of ATP production.
  • Excess glucose is stored as glycogen or converted to fat and stored in adipose cells.
  • No standardised RDI
    • Contributes ~ 2% of TBW
    • Consumes ~20% of glucose

Lipids (fat)

  • Major source of stored energy in body 38kJ/g
  • Cholesterol forms
    • Steroid hormones
    • Cell membranes
    • Bile
  • Phospholipids for
    • Cell membrane
  • No standardised RDI

Protein

  • Basic structural material of the body e.g. collagen, keratin
  • Many roles e.g.
    • Structural
    • Enzymes
    • Hormones
    • Carrier molecules
    • Haemoglobin
    • Contractile proteins
    • Antibodies
    • Energy
  • RDI 0.84g/kg/day for men
  • RDI 0.75g/kg/day for women

Essential Amino Acids

  • Histidine
  • Arginine
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Valine

Hormones

  • Oxytocin and Prolactin
  • Insulin and Glucagon
  • Thyroxine
  • Calcitonin and Parathyroid hormone
  • Antidiuretic hormone

Average Male

  • Approximately 76kg
  • 12kg protein (~15%)
  • 50-60% H_2O “everything else”

Protein Turnover

  • Continuous occurrence within the human body
  • Creates an ‘amino acid pool’
  • Rate of degradation may vary between proteins
  • Amino acids can be used to make Nitrogen containing compounds OR
  • Nitrogen can be pulled from amino acids to be used elsewhere

Nitrogen Balance

Protein:Nitrogen balance

  • Nitrogen intake - Nitrogen output

Positive Protein:Nitrogen balance

  • Nitrogen intake > Nitrogen output

Negative Protein:Nitrogen balance

  • Nitrogen intake < Nitrogen output