Growing older with health and vitality
Growing older with health and vitality: a nexus of physical activity, exercise and nutrition
The preservation of skeletal muscle mass and strength with advancing age are, we propose, critical aspects of ageing with health and vitality. Physical inactivity and poor nutrition are known to accelerate the gradual age-related decline in muscle mass and strength—sarcopenia—however, both are subject to modification. The main purpose of this review is to present the latest, evidence-based recommendations for physical activity and exercise, as well as diet for older adults that would help in preserving muscle mass and strength. We take the position that future physical activity/exercise guidelines need to make specific reference to resistance exercise and highlight the benefits of higher-intensity aerobic exercise training, alongside advocating older adults perform aerobic-based physical activity and household tasks (e.g., carrying groceries). In terms of dietary recommendations, greater emphasis should be placed on optimal rather than minimum protein intakes for older adults. Indeed, guidelines that endorse a daily protein intake of 1.2–1.5 g/kg BM/day, which are levels 50–90 % greater than the current protein Recommendation Dietary Allowance (0.8 g/kg BM/day), are likely to help preserve muscle mass and strength and are safe for healthy older adults. Being cognisant of factors (e.g., reduced appetite) that may preclude older adults from increasing their total daily protein intake, we echo the viewpoint of other active researchers in advocating that protein recommendations for older adults be based on a per meal approach in order to maximize muscle protein synthesis (MPS). On this basis, assuming three meals are consumed daily, a protein dose of 0.4–0.5 g/kg BM should be contained in each meal. We are beginning to understand ways in which to increase the utilization of ingested protein for the stimulation of MPS, namely by increasing the proportion of leucine contained in a given dose of protein, co-ingesting other nutrients (e.g., carbohydrate and fat or supplementation with n-3 polyunsaturated fatty acids) or being physically active prior to protein intake. Clearly, developing simple lifestyle interventions targeted at preserving muscle mass and strength with advancing age is crucial for facilitating longer, healthier lives into older age.
Humans’ lifespans are increasing due to improvements in healthcare. This has resulted in a larger aged population which has economic and social consequences.
Fundamentally, this ageing demographic is testament to continued improvements in healthcare services. However, a disproportionate use of healthcare services by older people highlights the economic cost of population ageing, alongside the high prevalence of morbidity that can reduce quality of life with advancing age. As a consequence, there is a perception that society (in some European countries more than others) often views older people as a societal and economic burden
Sarcopenia and the threat of physical disability
Symptoms of Sarcopenia:
- low skeletal muscle mass, muscle strength and physical performance = reduced mobility, strength, size
- results in poor balance, difficulty doing simple tasks, increased rates of falls
muscle mass loss increases with age. 40-70s – 8% per decade, >70 – 15% per decade
strength loss ~35% per decade for men and ~27% per decade for women.
- muscle/strength loss expedited by periods of inactivity/disuse due to injuries/weathers/life
- Net Muscle Protein Balance [Muscle Protein Synthesis (MPS) vs Muscle Protein breakdown] – Main determinant for muscle loss
- Increasing MPS – diet high in protein, physical activity and pharmaceutical anabolic agents
The onset of muscle mass loss typically begins by the fourth decade of life (Janssen et al. 2000), having peaked between 20 and 30 years of age. Thereafter, the average rate of muscle mass loss is estimated at 8 % per decade (~0.5–1 %/year) until the age of 70 years (Mitchell et al. 2012), increasing to ~15 % per decade in octogenarians and beyond (Delmonico et al. 2009). Hence, most individuals 70–80 years old possess only 60–80 % of the muscle mass they had at ~30 years old, declining to <50 % in octogenarians…. the trajectory of strength loss is even more precipitous, with annual declines of 3–4 % reported in men and 2.5–3 % in women (Goodpaster et al. 2006).
Refining physical activity and exercise guidelines
- Physical activity = better cardiovascular health, increased strength, reduced risk for chronic diseases
- Resistance exercise is effective for building both muscle mass and strength even in the elderly
Endurance exercise = better blood sugar levels, cardiovascular fitness and maybe has anabolic potential.
For instance, one study reported a significant increase in quadriceps muscle volume and muscle power in older individuals who cycled for 20–45 min, at 60–80 % heart rate reserve, 3–4 times per week for 12 weeks (Harber et al. 2012). Similarly, older women who performed 12 weeks of progressive cycling showed increased quadriceps size (~12 %) and aerobic capacity (~30 %) (Harber et al. 2009). It is important to acknowledge that other studies have failed to detect an impact of aerobic exercise training on muscle mass in older adults (Short et al. 2004; Sipila and Suominen 1995).
Optimizing the quantity of protein recommended on a per meal basis
- Older adults require more protein to stimulate MPS. (require more than 21g of protein per meal. ~40-50g)
- Balanced meal pattern = better MPS stimulation (eg. 40g/40g/40g > 20/30/50g)Important to reach/exceed leucine threshold to “switch on the muscle anabolic signalling proteins that stimulate MPS”
A recent study in young adults (Mamerow et al. 2014) demonstrated a greater 24 h response of MPS to a balanced meal pattern that distributed 90 g of protein evenly between three meals (3 � 30 g), spaced 3.5–4 h apart versus a conventional (Tieland et al. 2012; Valenzuela et al. 2013) skewed meal pattern that biased daily protein intake (~63/90 g) towards the evening mealAccordingly, a retrospective analysis of serial dose-response studies revealed the optimal relative dose of protein in a single serving for the maximal resting postprandial stimulation of myofibrillar-MPS to be 0.40 g/kg BM in older adults; ~68 % greater than calculated in young adults (0.24 g/kg body mass) (Moore et al. 2014). Thus, assuming three meals are consumed each day, a relative protein dose of 0.4–0.5 g/kg BM/meal is consistent with recent expert opinions concerning the optimal daily protein intake (1.2–1.5 g/kg BM/day) for healthy older adults (Bauer et al. 2013; Deutz et al. 2014).
Optimizing the quality and utilization of protein intake on a per meal basis
Why older adults have trouble hitting protein requirements:
- reduced appetite
- reduced ability to perform tasks – cooking, shopping, food prep
- satiating value of protein
Therefore need to emphasize Protein quality, the ability to stimulate MPS, determined by: AA profile, leucine content, bio-availability, digestibility.
From a protein quality standpoint, it is commonly accepted that a rapidly digested and leucine-rich protein source is best positioned to activate mTOR and stimulate a postprandial response of MPS.
Other nutrients may increase the utilisation of ingested protein
- Combined ingestion of fat and carbohydrate may enhance the utilisation of a suboptimal amount of EAA for MPS or even suppress MPB (Muscle Protein Breakdown)
- Omega-3s = potentiate MPS rates = increased strength
Optimizing protein recommendations on a daily basis
- higher protein = higher bone mass
- current RDAs too low
- lack of evidence that high protein intake = negative health outcomes
- studies suggest for older adults RDA = 1-1.5g/kgBW