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