Douglas Paddon-Jones, Ph.D.
The University of Texas Medical Branch
Dietary protein: guidelines, requirements
and a lack of common sense
1. protein metabolism
2. building muscle in response to a protein-rich meal
3. translating science into practice
4. priority areas: aging - physical inactivity – hospitalization
5. negative consequences of extra protein?
6. sarcopenia and a new strategy
Overview
Inactivity
Malnutrition
Balance
Synthesis
Breakdown
Muscle
growth
Muscle
loss
Nutrition
Exercise
Hormones
Maintaining Muscle Mass and Function
Illness/Injury
Stimulating Muscle Growth with Protein
Symons et. al. AJCN, 2007
* *
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Fasting
Pro
tein
Synth
esis
(%
/h)
Young
Elderly
50% increase
30 g protein
Protein Synthesis and Portion Control - a message of moderation -
* *
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Fasting 30 g protein
Pro
tein
Synth
esis
(%
/h) * *
Fasting 90 g protein
Young
Old
~1.2 g/kg/day for 180 lb individual
90 g protein 30 g protein
Symons et. al. AJCN, 2007 Symons et. al. JADA. 2009
Ne
t M
uscle
Pro
tein
Syn
thesis
(mg
Ph
e/leg
)
More than ~25 g protein
Age-related protein dose-response
0
10
20
30
40
50
60
Young
Elderly
Less than ~15 g protein
Katsanos et. al. AJCN, 2005
5 g
8 g
6 g
6 g
* *
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Fasting Protein meal
Pro
tein
Syn
thesis
(%
/h)
0.16
0.18
Young
Elderly
* *
Protein + Exercise
50% increase
100% increase
Synergistic Effect of Protein and Exercise
Symons et. al. JNHA, 2010
Timing of Protein and Exercise
Meal Appearance in plasma Peak anabolic window
Whey Protein
Amino Acids 10-20 minutes Consume 0-60 minutes post exercise
Intact Proteins
(beef, fish etc.) 120+ minutes
Consume approx.. 90 minutes before
exercise
* note, the timing relates only to muscle protein anabolism and does not take
into account practical issues such as exercise performance, satiety, gastric
comfort, hunger or coingestion of other nutrients.
Leucine Content of Foods
1 scoop (36 g) of whey protein isolate
3.2 g
1 scoop (36 g) soy protein isolate 2.4 g
4 oz. sirloin steak 2.0 g
4 oz. chicken breast 2.0 g
1 cup low-fat yogurt 1.1 g
1 cup fat-free milk 0.8 g
1 egg 0.5 g
2 tbsp. peanut butter 0.5 g
1 slice wheat bread 0.1 g
Sources: USDA National Nutrient Database for Standard Reference, Release 20. and GNC WPI 28
Optimizing meal anabolism with Leucine
0
0.05
0.06
0.07
0.08
0.09
Post-absorptive
Post-prandial
Day 1 (pre)
0.10
0.11
0.12
Day 14
( 2 weeks LEU)
P=0.02
P=0.04
Pro
tein
synth
esis
: %
/ h
r
Daily protein distribution - typical ? -
Total Protein
90 g
Cat
abol
ism
A
nab
olis
m
10 g
maximum rate of protein synthesis
15 g 65 g
A skewed daily protein distribution fails
to maximize potential for muscle growth
Daily protein distribution - Optimal -
Cat
abol
ism
A
nab
olis
m
maximum rate of protein synthesis
30 g 30g 30 g
Total Protein
90 g
Repeated maximal stimulation of protein synthesis increase / maintenance of muscle mass
~ 1.3 g/kg/day
Bed rest is a defacto treatment modality - if you’re hospitalized you become inactive -
Inactive
(0 steps/min)
Low Activity
(< 15 steps/min)
0
10
20
30
40
50
60
70
80
90
100
% of
Time
Inactivity and Aging Muscle
-1500
-1000
-750
-500
-250
0
250
Lo
ss
of
lea
n l
eg
ma
ss
(g
)
-2000
Healthy Young
28 Days Inactivity
2%
total lean leg mass
Healthy Elders
10 Days Inactivity
10%
total lean leg mass
Paddon-Jones et. al. 2004
Kortebein et al. 2007
3 times more
muscle loss
1/3 the time
All volunteers
consumed the
RDA for protein
Inactivity reduces muscle protein synthesis
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
Day 1 Day 10
Pro
tein
Synth
esis
(%
/h)
* 30%
Kortebein et al. 2007
24 h muscle protein synthesis during 10 day of inactivity in elders
(stable isotope methodology)
Protein combats inactivity-induced muscle loss
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
Day 1 Day 10
Pro
tein
Synth
esis
(%
/h)
*
Normal Diet Normal Diet Normal Diet +
Amino Acids
#
Normal Diet +
Amino Acids
30%
Ferrando & Paddon-Jones et. al. 2009
- older adults -
Are our older inpatients eating enough ?
0
20
40
60
80
100
Protein Carbohydrate Fat
Presented
Consumed
gra
ms
0
20
40
60
80
100
Protein Carbohydrate Fat
Presented
Consumed
gra
ms
per meal
Paddon-Jones, pilot data
Muscle Loss in Hospitalized Elders
-1500
-1000
-750
-500
-250
0
250
Lo
ss o
f le
an
leg
mass (
g)
-2000
Healthy Young
28 Days Inactivity
2%
total lean leg mass
Healthy Elders
10 Days Inactivity
10%
total lean leg mass 10+ %
total lean leg mass
Elderly Inpatients
3 days hospitalization
Paddon-Jones , Pilot Data
The Protein Myth
“Adults eat more protein than they need”
True: most adults eat more protein than the
minimum to prevent deficiencies
But: minimum needs ≠ optimum health
Dietary protein and Bone… the myth
Increased protein causes calciuria and will ultimately weaken bone
Dietary protein and Bone… the reality
Protein
Ca2+
[Ca2+]
+
• Moderate protein diets (1- 1.5 g/kg/day)
are associated with normal calcium
metabolism
• Low protein intakes ( 0.8 g/kg/day):
intestinal calcium absorption is reduced
and levels of parathyroid hormone
increase, causing the release of
calcium from bone Ca2+
Feskanich D, et al. Am J Epidemiol 1996;143:472-9. Cooper C, et al. Calcif Tissue Int 1996;58:320-25
Institute of Medicine:
“protein content of diet is not related to progressive decline in kidney function with age."
Protein and Renal Function
Sarcopenia: - traditional model -
20 30 40 50 60 70 80 5
10
15
20
25
30
35
Fat Mass
Age (years)
(kg)
20 30 40 50 60 70 80
30
35
40
45
50
55
Lean Body Mass
Age (years)
(kg)
Holloszy, Mayo Clin Proc. 2000
Alternate model of muscle loss - developing tactical nutrition interventions -
15
17
19
21
23
25
27
29
31
40 44 48 52 56 60 64 68 72 76 80 84 88
Age (yrs)
Lean m
uscle
mass (
kg)
Prevention and treatment strategies - muscle mass & function -
PREVENTION:
a). Consume a moderate amount of high-quality protein, 3-times per day
b). Consume protein in close proximity to physical activity
TREATMENT:
a). React aggressively with nutritional support to reduce the rapid loss of
muscle and strength associated with physical inactivity
Benefits of exercise and high quality protein are not age dependent
Distribution of protein throughout the day is key
Moderation and common sense are still the key theme
Hypertrophy is slow, but atrophy can be exceedingly fast
The RDA for protein is not sufficient in many circumstances
Summary
25-30 g of protein maximally stimulates muscle protein synthesis
Madonna Mamerow, Ph.D.
Fellow
Joni Mettler, Ph.D.
Fellow
Kirk English
Doctoral Student
Christopher Danesi
Coordinator
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