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Lecture 5' Macronutrients: Protein

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Title: Lecture 5' Macronutrients: Protein


1
Lecture 5. Macronutrients Protein
2
from last Lecture (RDIs)
  • AUSTRALIAN
  • RDI recommended dietary intakes
  • AMERICAN
  • DRI dietary reference intakes
  • Whitney Rolfes 10th Ed. (2005)
  • Inside front cover
  • RDA recommended dietary allowance
  • Whitney Rolfes 10th Ed. (2005)
  • Chapter 1 Dietary Reference Intakes (pp16-18)

3
Amino Acid structure
  • H
  • central carbon atom
  • H C H
  • H H H O
  • H C C C C C OH
  • organic acid group
  • H H H N Carboxyl group
  • side group H H
  • amino group

4
Protein
  • Basic unit AMINO ACID
  • Protein POLYPEPTIDE of 50-300
  • amino acids
  • eg. human Insulin has 51 amino acids (very small)
  • more complex larger molecules than CHO
  • due to side group

5
Amino Acids
  • 22 common amino acids in food
  • each has a different side group
  • Figure 6.2 (p. 183) Examples of Amino Acids.
    Whitney Rolfes 10th Ed.
  • constituent amino acids characterize a PROTEIN
  • eg. protein of BEEF muscle different to protein
    of PORK muscle
  • Figures 6-4 and 6-5 (p. 184), Structures of
    Insulin and Haemoglobin. Whitney Rolfes 10th
    Ed.

6
Amino Acids structural functional roles
  • cell membrane
  • connective tissue
  • (collagen elastin)
  • inert protein
  • (hair nails)
  • enzymes
  • blood proteins
  • (albumin haemoglobin)
  • antibodies
  • skeletal smooth muscle
  • 20 energy source

7
Protein
  • AAs continually synthesised catabolised in the
    body
  • daily turnover ?3 - 4g/kg body weight/day
  • dietary intake ? ¼ - ½ this amount

8
  • MOST Protein made from recycling amino acids
  • synthesise
  • new proteins essential, from food or
    already in body

9
Essential (indispensable) amino acids
  • new protein synthesis requires full complement of
    amino acids
  • cannot make part proteins
  • other AAs are wasted (deaminated)
  • most amino acids synthesised in the body
  • need Nitrogen for amine group
  • C-fragments H atoms from CHO or Fat molecules
    AND/OR from degraded AAs in the body

10
Essential (indispensable) amino acids
  • 8 (9 in children) cannot be synthesised in the
    body
  • ? MUST BE SUPPLIED FROM FOOD

11
Essential (indispensable) amino acids
  • Histidine (in children)
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Valine
  • branched chain
  • amino acids

12
Protein Quality
  • Definition
  • the amount of protein in a particular food its
    supply of essential amino acids
  • ANIMAL protein BEST QUALITY
  • supplies ALL 8(9) essential amino acids
  • usually the HIGHEST concentration

13
Protein Quality
  • PLANT protein LESSER quality
  • doesnt supply ALL essential amino acids
  • LOWER concentration
  • exception SOY PROTEIN

14
Plant protein cont...
  • combining LEGUME CEREAL protein will ensure ALL
    essential amino acids
  • each food contributes the essential AAs missing
    in the other food
  • COMPLEMENTARY PROTEINS
  • (Vegans)

15
Complementary proteins
16
Protein Quality
  • eg. Complementary proteins
  • baked beans and rice
  • peanut butter on bread (wheat)
  • refried beans Tacos (corn)
  • stir-fried vegetables rice

17
Protein requirements
  • 1 gram protein supplies 17kj
  • sedentary individuals
  • balanced diet 10-15 of Etotal from protein
  • athletes
  • balanced diet 12-17 of Etotal from protein

18
  • Sedentary individuals
  • or 0.8g - 1.0g protein/kg body weight/day
  • if weight 70kg
  • protein requirement will be
  • between 70 x 0.8 56g protein/day
  • and 70 x 1.0 70g protein/day

19
  • Athletes
  • elite endurance athletes
  • 1.2 - 1.4g protein/kg body mass/day
  • oxidisable fuel when CHO stores depleted
  • strength power athletes
  • 1.2 - 1.7g protein/kg body mass/day
  • maintains ve Nitrogen balance
  • AAs can be synthesised incorporated into
    required protein

20
Protein from food
  • Food Protein g/100g
  • HIGH CONTENT
  • Beef lamb 28
  • Cheese 26
  • Chicken 25
  • Fish 18
  • Eggs 12
  • Beans 7
  • Peas 5
  • Milk 3.3

21
  • Food Protein g/100g
  • MEDIUM CONTENT
  • Cornflakes 8.6
  • Bread (white) 7.8
  • Spaghetti 4.2
  • Sweetcorn 4.1
  • Rice 2.2
  • Cauliflower 1.6
  • Potatoes 1.6
  • Cabbage 1.3

22
  • Food Protein g/100g
  • LOW CONTENT
  • Apples 0.3
  • Honey 0.5
  • Butter margarine lt0.4
  • Wine 0.1
  • Soft drink 0

23
HOMEWORK
  • Sedentary individual (70kg body mass)
  • 56 - 70g protein/day protein FOOD
  • Endurance athlete (75kg body mass)
  • 90 - 105g protein/day protein FOOD
  • Strength Power athlete (100 kg body mass)
  • 120 - 170g protein/day protein FOOD

24
Recommended Reading
  • Whitney Rolfes (2005)
  • Understanding Nutrition 10th Ed.
  • Chapter 6 Protein Amino Acids
  • ENTIRE CHAPTER
  • AND/OR
  • Wahlqvist (2002)
  • Food Nutrition
  • Chapter 14 Protein
  • ENTIRE CHAPTER
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