9. Nutritional strategies to support skeletal muscle health in older adults Flashcards
explain age-associated loss of muscle mass and strength
GRAPH: muscle mass and strength (y-axis) vs age (x-axis, separated in 3 categories)
- compare age-related vs disease-related
- muscle mass decreases by ____% per year
- strength decreases by ____% per year
EARLY LIFE:
- growth and development to maximise peak muscle mass
- increase muscle mass/strength during puberty until you reach a max
ADULT LIFE:
- maintain peak
- slow decrease: try to minimize age-related muscle loss
- depends on exercise and diet
OLDER LIFE:
- minimizing loss
- continue decreasing
*healthy age-related decreases won’t be that big slope VS disease related aging: steep slope! –> can be problematic: when you reach threshold, will be institutionalized/dependent of others
at 40-50 yo –>
- muscle mass: -0.8% per year
- muscle strength: -2-3% per year
*nervous system plays a big role in muscle
- sarcopenia is a ____________
- is there a consensus in diagnosis? cons? (3)
- are there different definitions that exist?
- disease! (formally classified by international classification of diseases in september 2016)
- no global consensus criteria exist to define sarcopenia
1) prevents clinical diagnosis
2) prevents proper comparison of research studies (ie calculating prevalence)
3) defining treatment approaches - yes! different consensus groups have their own sarcopenia definitions (include or exclude muscle mass, strength and function + different cut-off points)
what is the conceptual definition of sarcopenia?
defined by which group?
- what are general aspects of sarcopenia? (lead to sarcopenia ish) (5)
- what are outcomes of sarcopenia (6)
- muscle mass + muscle strength + muscle-specific strength (ie muscle strength/muscle size –> force generating capacity of muscle per cross-sectional area)
- Global leadership initiative in sarcopenia (GLIS)
*operational definition coming soon (ie cut-offs)
- disease of skeletal muscle
- increase with age
- potentially reversible
- def does not depend on age, setting of care or clinical condition
- is the same for clinical practice and research
OUTCOMES:
- impaired physical performance (not part of sarcopenia definition!)
- mobility limitations (walking, transfer chair/bed)
- falls, fractures, hospitalizations, admissions to nursing home
- inability to perform instrumental and basic ADLs
- poor quality of life
- mortality
how to measure muscle mass (4), muscle strength (1) and muscle function (1)
MUSCLE MASS
- golden standard: MRI (or CT scan) but very expansive
- DEXA (not exactly measuring muscle mass –> measuring lean mass)
- D3-Cr (isotope labeled creatine) –> oral ingestion –> creatine stored in muscle –> more muscle = more stored creatine –> rest becomes creatinine –> measure urine creatinine
- Bioelectic impedance –> also measures lean mass (not muscle mass)
STRENGTH:
- grip strength
MUSCLE FUNCTION (although not part of GLIS definition)
- gait speed
what are the 2 primary anabolic stimuli for muscle?
- dietary protein (provides aa = building blocks)
- resistance exercise
explain synergy btw protein/aa and resistance exercise
- what happens to synthesis and breakdown when + net balance
a) REST
b) REST + AA
c) RESISTANCE EXERCISE
d) RE + AA
a) REST:
- synthesis: medium (30)
- breakdown: higher than synth (45)
NET: negative
b) REST + AA
- synthesis: higher! (50)
- breakdown: lower! (35)
NET: positive!
c) RESISTANCE EXERCISE
- synthesis: higher! (60)
- breakdown: higher! (62)
NET: negative
d) RE + AA
- synthesis: super high! (70)
- breakdown: lower (40)
NET: positive!
conclusion: best protein synthesis when RT and AA!
*numbers are arbitrary
older adults have anabolic resistance to which 2 things?
- explain
TO PROTEIN INTAKE
- older adults have a smaller increase in protein synthesis after eating a meal! (vs younger adults have a big increase from resting to post-prandial)
- diminished anabolic stimulus!
TO INSULIN!
- insulin = anti-proteolytic = suppresses protein breakdown!
- when you inject 15IU insulin in young adults: BIG decrease in protein breakdown VS in older adults: barely a decrease in protein breakdown
- older adults: less effective suppression of protein breakdown
what is the relative per meal protein intake to maximise MPS?
- young vs older
protein recs for older people? >65:
- healthy?
- very active
- acute/chronic disease
- what is the RDA for adults? vs EAR
what is RDA?
YOUNG:
- 0.24 g/kg (19.2g for 80kg male, 14.4g for 60kg female)
OLDER:
- 0.40 g/kg per meal! (ie 32g for 80kg male, 24g to 60kg female)
- healthy: 1-1.2g/kg/d
- very active: >1.2g/kg/d
- acute/chronic disease: 1.2-1.5 g/kg/d
- EAR = 0.66g/kg/d
- RDA = 0.8g/kg/d –> prevents deficiency in 98% of population (but we technically want to achieve optimal muscle health, not just prevent deficiency)
explain the indicator amino acid oxidation method (graph)
- what do recent studies show for EAR vs RDA (3 different set of values)
- inject tracer phenylalanine –> low protein intake = low protein synthesis = high C-oxidation (measured from CO2 from breath)
- as protein intake increases, protein synthesis increases and C-oxidation decreases
- until reach a plateau –> the breakpoint = recommendation
EAR:
a) 1.1 g/kg/d (women 80-87)
b) 0.96 g/kg/d (women >65)
c) 0.94 g/kg/d (men >65)
RDA:
a) 1.15 g/kg/d (women 80-87)
b) 1.29 g/kg/d (women >65)
c) 1.24 g/kg/d (men >65)
is there an added benefit of protein supplementation during RE training for older adults? 2 different studies
study 1:
- positive effect of prot. suppl!
- increase 0.48 kg (of muscle mass?)
study 2:
- no additional gain from protein suppl
- but maybe supplement dose is too low (20g/day)
do older adults usually respect the protein RDA? what percentage:
- <0.8 g/kg/d
- < 1.0 g/kg/d
- < 1.2 g/kg/d
not really….
- <0.8 g/kg/d: 20% ish of people don’t reach
- < 1.0 g/kg/d: 40-50% don’t reach
- < 1.2 g/kg/d: 65-70% don’t reach…
what 2 factors make up protein quality?
- ___________ is used to compare different protein sources
- a value of 100% means what?
- which types of protein are considered high quality?
- essential aa content + digestibility (absorption, make sure its bioavailable)
- DIAAS (digestible indispensable aa score)
- 100% means that the dietary rec of the most limiting essential aa in test protein would be met by the dietary intake of 0.66 g/kg/d of that protein!
*values greater than 100% are considered high quality protein - whole milk, milk protein, casein, whey, egg, beef, soy protein! –> mostly all animal!
VS plant proteins = lower quality bc missing essential aa
what do studies comparing animal vs plant protein show in terms of protein synthesis rate? (2 studies)
study 1:
- ingesting 20 or 40g protein, at rest or at exercise, whey protein leads to bigger synthesis rate compared to soy
study 2: (more recent)
- compare collagen, whey and pea –> 2 x 25g per day
- collagen = no stimulatory effect
- whey and pea –> NO difference!
- BUT, con of the study: a controlled diet of protein intake set at RDA for 7 days (before adding suppl)
do vegan diets compromise MPS rates in older adults?
- same protein synthesis rate for vegan vs omnivore groups!
- BUT participants were highly active (>12 000 steps/d) + daily protein intake of 1.2-1.3 g/kg/d
- what are 2 protein intake distributions in older adults?
- which one is better?
SKEWED:
- very low protein at breakfast (10-15g)
- medium at lunch, but still below threshold of 0.4g/kg per meal (ie 20g)
- very high at dinner! (ie 60g)
EVEN protein distribution:
- 30g protein every meal
- greater protein synthesis for even protein distribution!
what is the new supplement that could have benefits for muscle health?
- mechanisms? (2)
omega-3 fatty acids!
1) omega-3 FA sensitize muscle to the anabolic actions of aa! –> much bigger protein synthesis rate compared to corn oil (control)
2) omega-3 FA increase muscle size and strength
- increase in thigh muscle volume, handgrip strength and 1RM strength compared to control, after 6 months!
SUMMARY - nutrition strategies to support muscle health
- is there a globally accepted operational definition of sarcopenia? consequences?
- older adults display ___________ _________ –> they are less sensitive to WHAT? but retain capacity to WHAT
- older adults may required greater per meal (HOW MUCH g/kg) and per day (HOW MUCH g/kG) protein intake to robustly stimulate MPS and support muscle mass maintenance
- which protein sources can stimulate MPS rates? (aim for ___g which aa per meal)
- which protein distribution MAY better support __________ responses compared to the other distribution
- emerging evidence that ___________ may have ________ actions –> more research needed
- NO! –> makes diagnosis and treatment and research difficult
- anabolic resistance! less sensitive to anabolic properties of dietary protein BUT retain capacity to respond if enough protein is provided
- 0.40g/kg per meal + 1.2g/kg per day
- both animal and plant-derived proteins can stimulate MPS rates (aim for 2.5g leucine (key aa that regulates MPS) per meal)
- even! MAY better support muscle anabolic responses vs skewed
- omega-3 FA may have anabolic actions
