douglas paddon-jones, ph.d. associate professor, physical therapy and internal medicine the...
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Douglas Paddon-Jones, Ph.D.
Associate Professor, Physical Therapy and Internal Medicine
The University of Texas Medical Branch
Protein Intake and the Preservation of Muscle Mass in
Aging
Iowa Dietetic Association 2009
Overview
muscle protein metabolism – the science
translating science clinical practice
protein needs - healthy aging
- physical
inactivity
- exercise
Inactivity
Malnutrition
Balance
Synthesis
Breakdown
Muscle growth
Muscle loss
Nutrition
Exercise
Hormones
Maintaining Muscle Mass
Illness/Injury
Age and body composition
20 30 40 50 60 70 805
10
15
20
25
30
35
Fat Mass
Age (years)(k
g)
20 30 40 50 60 70 8030
35
40
45
50
55Lean Body Mass
Age (years)
(kg
)
FrailtyFrailty
¯ lean body mass¯ lean body mass
fat mass fat mass
insulin resistance insulin resistance
visceral fat visceral fat
Decreased muscle mass
Decreased muscle mass
type 2 diabetes type 2 diabetes
¯ strength¯ strength
¯ power¯ power
¯ risk of falls¯ risk of falls
¯ risk of fractures¯ risk of fractures
¯ walking speed¯ walking speed
Dietary strategies to maintain muscle
Free-form amino acid
supplements:
stimulate muscle anabolism
they are effective in all age groups
they can be used clinically
Breakfast Lunch Dinner
? ??
How much protein are we getting ?
Muscle Protein Synthesis / Muscle Growth- protein ingestion -
Symons et. al. AJCN, 2007
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Fasting
Pro
tein
Syn
thes
is (
%/h
)
YoungElderly
30 g protein30 g protein
?
Protein Ingestion and Muscle Growth- 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
esi
s (%
/h)
Fasting 90 g protein
YoungOld
~1.2 g/kg/day for 180 lb individual
Daily protein distribution- typical ? -
Total Protein 90 g
Cata
bolis
mA
nabolis
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 -
Cata
bolis
mA
nabolis
m
maximum rate of protein synthesis
30 g 30g 30 gTotal Protein
90 g
Repeated maximal stimulation of protein synthesis increase / maintenance of muscle mass
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Fasting Protein meal
Pro
tein
Syn
thes
is (
%/h
)
0.16
0.18
YoungElderly
Protein + Exercise
Protein + Exercise
? ?
Bed rest is a defacto treatment modality- if you’re hospitalized you will become inactive -
Inactive(0 steps/min)
Low Activity(< 15 steps/min)
0
10
20
30
40
50
60
70
80
90
100
% of Time
Muscle Loss in Bedridden Elders- 10 Days of Inactivity/Bed rest -
-1500
-1000
-750
-500
-250
0
250
Los
s of
lean
leg
mas
s (g
)
-2000
Young 28 Days Bedrest
2% total lean leg mass
Elderly10 Days Bedrest
Paddon-Jones et. al. 2004Kortebein et al. 2007
?
Muscle Loss in Hospitalized Elders
-1500
-1000
-750
-500
-250
0
250
Los
s of
lean
leg
mas
s (g
)
-2000
Young 28 Days Inactivity
2% total lean leg mass
Healthy Elders10 Days Inactivity
Elderly Inpatients~ 3 days
? ?
Inactivity reduces the ability to build/repair proteins and muscle
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
esi
s (%
/h)
*
Kortebein et al. 2007
24 h muscle protein synthesis during 10 day of inactivity in elders (stable isotope methodology)
What are our older inpatients eating ?
0
20
40
60
80
100
Protein Carbohydrate Fat
Presented
Consumed
gram
s
0
20
40
60
80
100
Protein Carbohydrate Fat
Presented
Consumed
gram
s
per meal
Can we reduce muscle loss associated withinjury/inactivity using dietary protein ?
Paddon-Jones et al, 2004
Muscle Mass
-0.6
-0.4
-0.2
0
0.2
0.4
0.6C
han
ge
in le
g m
usc
le m
ass
(kg
)
Bedrest Bedrest +Amino acids
Paddon-Jones et. al. 2004
?
Strength
-25
-20
-15
-10
-5
0
5L
oss
of
1RM
Leg
Ext
ensi
on
str
eng
th (
kg)
Bedrest
Paddon-Jones et. al. 2004
?
Bedrest +Amino acids
Can protein also help elders?- 24 h 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
Syn
thesis
(%
/h)
*
Normal Diet Normal Diet Normal Diet +Amino Acids
#
Normal Diet +Amino Acids
Regular meals + 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)
Pro
tein
sy
nth
es
is:
% /
hr
?
Hot topic: Leucine plays a key role
Distribution of protein throughout the day plays a key role
Moderation and common sense are still the key themes
Muscle growth is a slow process, but atrophy can be exceedingly fast
The RDA for protein is not sufficient in many circumstances
Summary
~ 30 g of protein maximally stimulates muscle protein synthesis
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