Protein Intake And Metabolism Flashcards
AMDR for 1-3 years of age
45-65% CHO
5-20% protein
30-40% fat
ADMR for 4-18 yrs
45-65% CHO
10-30% protein
25-35% fat
ADMR for 19 years and older
45-65% Cho
10-35% protein
20-35% fat
Practical issues/concerns with using 10-35% of total calories for protein
- how would you know what to eat
- how much protein to have at one time
- would need to calculate energy needs (kcal/day)
What do most sport dieticians do to calculate AMDR for protein
Use values based on an athletes body weight
Example: energy needs 2,500 kcal/day, 21 yrs, protein range 250kcal to 875kcal
10%= 250kcal/4kcal per gram = 62.5g/day
35%= 875kcal/4kcal per gram = 218g/day
9 Protein functions
- Structural
- Transport
- Enzyme
- Hormone/neurotransmitter
- Immune
- Acid-base balance
- Fluid balance
- Energy (4kcal/g)
- Movement (skeletal muscle)
Structural
Vital constituents of all cells
Transport proteins
Of various substances in the blood
Protein for enzymes
Form almost all enzymes in the body
protein for hormone/neurotransmitters
Formation of insulin, etc
Protein for immune
Formation of antibodies, etc
Protein for acid-base balance
Buffering within the blood to maintain optimal pH
Protein for fluid balance
Exerting osmotic pressure to maintain optimal fluid balance within the body
What does protein contain
C,H,O and nitrogen
What does protein digestion enable
Amino acids to enter the “amino acid pool”
- blood, liver, peripheral tissues (i.e. muscle)
- broken down to AAs
Amino acids in one area are in constant
Equilibrium with another (tightly regulated)
Upon food digestion, how are proteins degraded
To amino acids by proteases (enzyme) in stomach and small intestine
What is protein broken down to in stomach
Polypeptides
What are polypeptides broken down into
Tripeptides, dipeptides, amino acids
Where does final breakdown to amino acids happen
In small intestine
Where are the amino acids absorbed
In portal vein and transported to liver
(Liver is critical centre in AA metabolism)
What is constantly clearing and moving AAs around body
Liver
How fast amino acids cleared once enter blood
5-10 mins
- certain digested quicker than others
Rate of digestion of protein is dependent on
Protein type and composition of the meal/snack
Fast absorption protein
Induce a large increase in whole body protein synthesis and oxidation with minimal affect on whole body protein breakdown
Example of fast absorption proteins
Whey or soy protein
Slow absorption protein
Induces a change in whole body protein turnover, small increase in synthesis and oxidation and a large reduction in protein breakdown
Example of slow absorption protein
Casein (e.g., chunks in cottage cheese)
How many amino acids
20
What is necessary for protein synthesis
All 20 amino acids
How many indispensable amino acids/essential amino acids (EAA)
9
What kind of AAs cannot be made in body
Indispensable amino acids/essential amino acids (EAA)
3 branches chain amino acids (BCAA) (are also EAAs)
Leucine
Isoleucine
Valine
What is ‘complete dietary proteins’
Food that contains all 9 EAAs
- e.g., meat
Examples of 10-20g protein
2 eggs
3/4 cup Greek yogurt
48 almonds
1 1/2 cup tofu
Plant sources of protein may result
In lower muscle protein synthetic response vs. Animal based protein
Why may animal protein result in lower muscle protein synthetic response
EAA profile (lower leucine content)
Lower digestibility
To get the quality of animal based protein what may you have to do with plant sources of protein
Portions may need to be larger
What do you have to do with plant based dairy products
Check label
Make sure there is protein, calcium, vit d
What do most nut based dairy products have
Low protein content
Nitrogen balance
Ability of body to retain nitrogen (protein balance)
If in balance must be getting enough protein
How to measure nitrogen balance
Dietary input (grams N2/day) = amount excreted
- amount consumed matches amount in urine
Negative nitrogen balance
Amount excreted > dietary input
Examples for negative nitrogen balance
Disease state, trauma, over-training
Individual is losing muscle protein
Positive nitrogen balance
Retaining protein to support growth and development
Dietary input > amount excreted
E.g. adults on caloric sufficient diet
How can nitrogen balance usually be maintained
When consuming 0.8 g/kg BW/day of protein in sedentary individuals (RDA)
Nitrogen balance depends on
Adequate protein intake and total energy intake (kcal/day)
Need adequate nitrogen and amino acids
A diet deficient in energy (kcal), despite adequate protein will result in
A negative nitrogen balance
How long is protein digestion
Can take several hours
Fat, fibre, and protein can slow digestion down
What is the most important metabolic fate of amino acids
Formation of body tissues, hormones, enzymes, antibodies, nucleotides, etc
Why can humans not store amino acids
Due to inability to store excess nitrogen
Since humans do not store AAs what occurs
Process of deamination in liver
Deamination
Nitrogen (amino group) on the amino acid is removed leaving a carbon molecule (alpha-ketoacid) for oxidation
What happens to excess nitrogen
Must be excreted
So the liver forms ammonia (NH3) from excess nitrogen
What is pool of AAs in blood broken down into
Nitrogen and carbon residue(alpha keto acid) because of deamination
What does nitrogen become
Urea (excretion)
What happens to carbon residue (alpha ketoacids)
Become CHO
Or oxidized for energy
What happens to the nitrogen group that travels to the liver in protein digestion
Gets converted to ammonia (NH3) and then converted to urea then enters kidneys to be excreted in urine
What have increased levels of ammonia been associated with
Fatigue
Glucogenic amino acids
Amino acids that can be used to form glucose via gluconeogenesis
Ketogenic amino acids
Amino acids that are metabolized to acetyl-CoA and can enter the Krebs cycle or be converted to fat and used for energy
What Alamo forms other nitrogen containing compounds
Amino acids
What can liver use nitrogen-containing amino groups from excess AAs for
Combine them with alpha-ketoacids (from fat or CHO metabolism)
When would an athlete need to use protein as a fuel source
Starvation
During low CHO diets and starvation/fasting, crash diets what can happen
Fat and lean tissue can be used to fuel body
- when total amounts of CHO/fat/total calories limited
Loss of lean tissue
Loss of strength/endurance, compromised immune/endocrine/musculoskeletal function
When CHO availability is low=
Increased reliance on muscle/body protein stores for energy
If an exercising individual wishes to maintain muscle mass what is essential
To not only have adequate protein for muscle growth but all sufficient CHO, fat and total calories
What do calories from CHO and fat create
A protein sparing effect
Low CHO diet may cause
Muscle protein to be oxidized for energy
- muscle
- liver (glucose or acetyl-CoA formation)
Exercise may increase
Protein losses
- urinary, sweat, gastrointestinal
What happens to protein at rest and exercise
Generally not oxidized to great extent and only contributes to ~5% of energy during exercise
As intensity/duration increases what happens to protein
Increased protein catabolism when muscle glycogen depleted
Although protein ca be incorporated to produced vast amounts of ATP what is problem
Rate of energy production is very slow vs CHO/fat
In later stages of prolonged endurance exercise how much energy does protein supply
Up to 15%
What does an increase in exogenous CHO intake during prolonged endurance exercise create
A muscle protein sparing effect
- inhibition of enzymes for protein breakdown
