KIN 110
Human Performance
and Nutrition
Lecture 12 – Protein
Greg Grinnell
gregorygrinn@umass.edu
Announcements
Read Ch. 7 in Nancy Clark (Protein)
Section 1: Exam 2 is Wed. Oct 21st
Sections 2 & 3: Exam 2 is Thu. Oct 22nd
Review
How can you shift your fuel use towards using more fat during
moderate to high intensity exercise?
A. Strength training
B. Endurance training
C. Eat a low CHO diet
D. All of the above
E. Only B & C
Review
How can you shift your fuel use towards using more fat during
moderate to high intensity exercise?
A. Strength training
B. Endurance training
C. Eat a low CHO diet
D. All of the above
E. Only B & C
Review
What is your body’s preferred energy source during most exercises?
A. Fat
B. CHO
C. Protein
D. It doesn’t matter
Review
What is your body’s preferred energy source during most exercises?
A. Fat
B. CHO
C. Protein
D. It doesn’t matter
Review
What is your body’s preferred energy source at rest?
A. Fat
B. CHO
C. Protein
D. It doesn’t matter
Review
What is your body’s preferred energy source at rest?
A. Fat
B. CHO
C. Protein
D. It doesn’t matter
Review
RER of 1.0 means that…
A. Mainly CHO is being used for energy
B. Mainly FAT is being used for energy
C. You are breathing out the same amount of carbon dioxide that you are
breathing in oxygen
D. A & C
E. B & C
Review
RER of 1.0 means that…
A. Mainly CHO is being used for energy
B. Mainly FAT is being used for energy
C. You are breathing out the same amount of carbon dioxide that you are
breathing in oxygen
D. A & C
E. B & C
Protein Roles
All PRO = functional
• Antibodies for immune system
• Enzymes
• Transporters
• Cell growth
• Build/repair muscles and bones
Therefore, a PRO deficiency is very serious!
Protein = chain of amino acids
Basic structure of an amino acid (AA):
Variant, side group.
Unique for each AA
Types of AA
Essential amino acids =
Not synthesized in body; HAVE
to come from diet
(about 9 of the 20 amino acids
are essential)
Non-essential amino acids = can
be synthesized from
other AA in the body
(11/20 AA)
Types of Protein
• PRO from animal sources = complete protein-contains all essential AA
(meat, dairy products)
• PRO from plant sources = incomplete protein-missing/contains low
levels of 1+ essential AA (beans, tofu, nuts and seeds)
•
Vegetarians & vegans need to pay more attention to PRO intake
Examples:
beans (low in methionine) vs.
corn, rice (low in lycine)
What if you combine the two?
You can eat multiple sources of incomplete proteins to get your complete
protein package! (i.e. 2 halves make a whole)
How is PRO used?
Alanine and other BCAAs enter energy pathways
 converted to acetyl CoA
Glycogen
Triglyceride
Glucose
Fatty acid
Pyruvate
Alanine
Other BCAAs
Fatty acyl CoA
Acetyl-CoA
ATP+ CO2 + H2O
How is PRO used?
Entry of A.A. can “replace” some of the
Acetyl CoA coming from CHO.
In most situations, contribution from PRO is
3-7 % of Total Energy
What situations increase contribution of PRO as an
energy source?
1. Exercise
2. Low energy, low CHO diets and starvation
Exercise & PRO use
Use of PRO goes up during exercise
Increased
PRO
use isused
closely tied to glycogen
Increased intensity,
more
protein
concentration
Increased duration, more protein
used
Low glycogen  more PRO use
Why?
Exercise & PRO use
% PRO use
Exercise Duration / Intensity
Does this remind you of another macronutrient?
Increased PRO use is closely tied to glycogen concentration
(low glycogen  more PRO use)
Low CHO diets and Fasting vs. PRO use
Increases PRO use
10-12 hours without food reduces liver glycogen by 50%.
If persistent low protein in diet, outcomes range fromIncreased PRO use is closely tied to glycogen
concentration
Low glycogen  more PRO use
Energy value for PRO
Total (potential) energy = 5.25 kcal/gram.
But:
PRO only 92-94% digestible (lower for plant PRO)
Lose 0.4 kcal/g
So, “digestible” energy = 4.85 kcal/g
BUT: energy in the Nitrogen group (0.85kcal/g) cannot be
metabolized
NET energy: 1 g PRO = 4 kcal/g
Energy systems
Creatine phosphate/ATP
Glucose/Glycogen
Stored fat
Protein
*PRO: you have to pay back!!!*
How to estimate PRO used during exercise
Measure nitrogen
in sweat during
Exercise
• Nitrogen = part
of AA
Standing PAUSE AND CHECK
•What is unique about the structure of an AA?
•How much energy is contained in an amino acid? How much of it is available for
use and WHY?
•What are the 2 types of amino acids? And the two types of PRO?
•What are the major differences between animal and plant sources of protein?
•How and Why does exercise affect the contribution of protein to energy
expenditure? (hint: intensity)
•How can PRO contribute to ATP (energy) production? How much does protein
contribute to energy expenditure under normal conditions? What situations
increase the contribution of protein to energy expenditure?
Protein dose – How much protein/day?
RDA of PRO intake (Nancy Clark, p. 139)
•
•
•
•
•
•
Sedentary adult: 0.8 g/kg/d
Recreational exerciser (adult): 1.1-1.6 g/kg/d
Endurance athlete (adult): 1.3-1.6 g/kg/d
Adults building muscle mass: 1.6-1.8 g/kg/d
Athletes restricting calories: 1.8-2 g/kg/d
Estimated upper req. for adults: 2 g/kg/d
Sedentary: 0.8 g PRO / kg / day
Active: 1.1-2.0 g PRO / kg / day
Do the math (in teams)150 lb active person, 1.2 g pro /kg/day → ???
Find a food equivalent of this amount of protein
Protein dose – How much protein/day?
Protein
surplus
+
even
Protein
deficit
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
grams protein / kg body wt. per day
Is 0.4 g/kg/day of protein sufficient?
•No. Hair/nails grow slowly. Recycling of AA
We reach PRO balance at 0.6-0.8 grams/kg/day. RDA = 0.8g/kg/d
Is the RDA sufficient for athletes?
•Probably NOT
•Athletes need ~1.2-2.0 g PRO/ kg/ day
•What do athletes need PRO for?
1.Increase muscle mass (strength and power athletes)
2.Balance increased use of PRO for energy when CHO is low (endurance
athletes)
3.Repair of muscle damage (strength/power AND endurance athletes)
Protein Turnover
Free Amino
Acid Pool
A
A
Protein
Supplied
by the
Body
A
A
A
A
A
A
A
A
A
A
A
A
Protein
Supplied by
Food
Protein Synthesis
PRO Synthesis & breakdown =
related b/c of free AA pool
Therefore, protein CANNOT be stored as an energy source!
Muscle Protein Balance
Net Protein Balance
difference between rates of protein synthesis (PS)
and protein breakdown (PB)
+
-
Positive Net Balance
PS > PB = lean body mass gain
Negative Net Balance
PB > PS = lean body mass loss
+
-
Protein Balance During
Feeding and Fasting
• PRO turnover constantly changing
based on fasted vs. not fasted state.
• Net PRO balance = important
Phillips SM et al., J Am Col Nutr, 2005
Resistance Exercise and Protein Work
Together to Promote Muscle Gain
PRO Balance
Resistance exercise + PRO
Rest + PRO
Exercise effect->
{
Protein gains
Exercise
Rest
Protein loss
Balance
Protein gains
Higher positive protein balance
Phillips SM., Nutrition, 2004
Meal
Meal
Meal
Protein loss
Dose: How much protein PER MEAL?
• The following study results are from Areta et al., 2013
• There are major differing opinions on these
conclusions!
Dose: How much protein PER MEAL?
So. . . How should you divide this throughout the day?
Discuss in teams & choose the best one…
150 lb person, 1.2 g/kg/day → 82 g/day (i.e. ~12oz steak)
- 3oz steak = a deck of cards
8 × 10 g every 1.5 h
or
4 × 20 g every 3 h
or
2 × 40 g every 6 h
Dose: How much protein PER MEAL?
Which group has the most gains (M-FSR)?
2 × 40 g every 6 h
4 × 20 g every 3 h
8 × 10 g every 1.5 h
What does this graph mean?
20 grams = maximum protein
synthesis stimulation at one time
(20 g max for a single dose)
Dose: How much protein PER MEAL?
• Schoenfeld & Aragon (2018) argue that “…it is important to
note that a number of factors influence dietary protein
metabolism including the composition of the given protein
source, the composition of the meal, the amount of protein
ingested, and the specifics of the exercise routine.”
• Total protein intake over the 12-h study period was only
80g
•Less than 1g/kg of body mass
•Far below the amount necessary to maximize muscle protein
balance in trained people
Protein timing: Does it matter when you consume protein?
A
Pre-exercise
Post-exercise
VS.
B
Protein before bed
First thing in morning
Subjects: Recreational male bodybuilders
Training status: 3-5 days/week for ≥ 6 months
Advantages to each timing method?
Which will result in bigger lean mass (muscle) gains?
Protein timing: Does it matter when you consume protein?
PAUSE AND CHECK
•Protein excretion on a “zero protein” diet is 0.4 grams of protein per
kg of body weight per day. Is feeding this quantity of protein enough to
maintain normal protein balance? Why or why not?
•How much protein is needed to maintain protein balance in the
average person? (i.e. How much protein do you need?)
•What is the RDA for PRO intake for both sedentary and active
populations? Is the RDA sufficient for athletes/active individuals?
•Why do athletes need extra protein?
•What is the proper dose for PRO intake per meal?
•What is the best timing for PRO intake?