Proteins – Let's build
those muscles
Study Unit 5 - NUT1501
Free PowerPoint Templates - prezentr.com
Main functions of protein in the body
Remember 1 g of protein = 17 kJ
l
Source of energy
l
Long-term energy reserve
l
Growth, maintenance & repair of body tissues
l
Basic building block* of muscles, connective tissue, bones, blood,
skin, hair, nails, hormones & enzymes
* Amino acids are the smallest
building blocks of protein.
Three main types
1) Essential amino-acids can’t be synthesized by the body, therefore it is
essential to get them from the diet. There are only 9 essential amino-acids.
1) Non-essential amino-acids can be synthesized by the body, therefore not
essential to get from the diet.
Refer to Figure 5.1 in the Study Guide for
specific examples of each type,
especially the 9 essential amino acids.
1) Conditionally essential amino-acids
2)are usually not essential (therefore they
3)can be produced by the body), but under special circumstances (such as
disease) they may become essential to get from the diet.
Chemical reactions & processes
Refer to pg 165 – 168 in the textbook.
Protein denaturation - When proteins are exposed to
heat (e.g. boiled eggs) or acid they uncoil and lose their
shapes.
Deamination – When amino-acids are broken down,
ammonia is produced which can be excreted by
the kidneys.
Transamination – When amino-acids are converted into other
amino-acids.
Nitrogen balance
Starvation
Critical illness
Refer to pg 176 - 179 in the textbook.
When glucose is formed from amino-acids
Gluconeogenesis
Breakdown / loss of protein stores (e.g. muscles)
PEM
Negative nitrogen balance
(More nitrogen is used than is being supplied by the diet)
Correct a negative nitrogen balance with:
↑ CHO intake + adequate fats (to spare protein)
↑ Protein intake (to replenish protein stores again)
Recovery from illness
Pregnant women
Children
Body builders
Protein stores are filled / replenished
Positive nitrogen balance
Protein quality
Refer to pg 179 - 180 in the textbook.
Is the protein easily absorbed / digested or not?
l
l
l
l
High quality protein
Easily digested & properly absorbed
E.g. red meat, chicken, fish, eggs,
soya & legumes
High biological value (BV):
> 70 = able to meet the body's need
for essential amino-acids
l
l
l
Low quality protein
Poorly digested / absorbed
E.g. vegetables & starches
Low biological value (BV):
< 70 = low in essential amino-acids,
not able to meet the body's need.
Complementary proteins – Two incomplete proteins eaten together
to improve their protein quality e.g. legumes + grains
Health effects
↓ Protein intake:
- PEM (e.g. kwashiorkor,
Marasmus & marasmic
kwashiorkor)
Remember the AMDR is 10 – 35%.
Refer to pg 180 - 184 in the textbook.
↑ Protein intake:
- Heart disease (especially
↑homocysteine intake)
- Cancer
- Obesity
- Osteoporosis
- Kidney stones
Protein Energy Malnutrition (PEM)
l
l
l
l
l
l
Marasmus
Infancy (< 2 yrs)
Develops slowly
Severe nutrient
deprivation / impaired
absorption
Severe weight loss &
muscle wasting with no
body fat
No edema (fluid
retention)
Good appetite possible
l
l
l
l
l
l
Kwashiorkor
Marasmic Kwashiorkor
Older infants (1-3 yrs) l Combination of
Rapid onset
marasmus &
Inadequate protein
kwashiorkor
intake / infections
l Often caused by both
Some weight loss &
malnutrition &
muscle wasting,
infections
retention of some body l Edema of kwashiorkor
fat
with the wasting of
Edema
marasmus
Loss of appetite
Recommended intakes
Refer to pg 184 - 187 in the textbook.
“Eat dry beans, slit peas, lentils and soya regularly’ &
“Meat, fish, chicken, milk and eggs can be eaten every day’ (FBDG's)
Focus on:
l 400–500 ml milk / dairy products per day
l 2 – 3 servings of fish per week
l 4 eggs per week and alternatively
l < 560 g of meat per week
Preferably low fat products and use fat
sparingly in the preparation.
[Dried beans & soya are good quality protein and can be used to substitute
animal protein sources in the diet]