Background: Studies have shown that an even protein intake distribution across meals increased 24-h muscle protein synthesis in young adults compared

Aging is associated with sarcopenia and functional decline, leading to frailty and disability. As a modifiable risk factor, nutrition may represent a target for preventing or postponing the onset of these geriatric conditions. Among nutrients, high-quality protein, leucine, vitamin D, and omega-3 polyunsaturated fatty acids (n-3 PUFA) are of particular interest for their demonstrated effects on skeletal muscle health. This narrative review aims to examine the recent observational and interventional evidence on the associations and the role of these nutrients in the muscle mass, strength, mobility, and physical function of free-living older adults, who are either healthy or at risk of frailty. Recent evidence supports a higher protein intake recommendation of 1.0–1.2 g/kg/day in healthy older adults; an evenly distributed mealtime protein intake or minimal protein per meal may be beneficial. In addition, vitamin D supplementation of 800–1000 IU, particularly when vitamin D status is low, and doses of ~3 g/day of n-3 PUFA may be favorable for physical function, muscle mass, and strength. Reviewed studies are highly heterogenous, yet the quantity, quality, and timing of intakes should be considered when designing intervention studies. Combined protein, leucine, vitamin D, and n-3 PUFA supplements may convey added benefits and may represent an intervention strategy in the prevention of sarcopenia and functional decline.

Background: Functional status declines with aging, thus impeding autonomy. Recently, a more even mealtime distribution of dietary protein was positively associated with muscle mass, but the relation of this distribution to physical performance remains unknown.

Obesity is associated with an increase in the fractional contribution of gluconeogenesis (GNG) to glucose production. We tested if this was related to the altered protein metabolism in obesity. GNG_PEP (via phosphoenol pyruvate [PEP]) was measured after a 17-h fast using the deuterated water method and ²H nuclear magnetic resonance spectroscopy of plasma glucose. Whole-body ¹³C-leucine and ³H-glucose kinetics were measured in the postabsorptive state and during a hyperinsulinemic-euglycemic-isoaminoacidemic clamp in 19 (10 men and 9 women) lean and 16 (7 men and 9 women) obese nondiabetic subjects. Endogenous glucose production was not different between groups. Postabsorptive %GNG_PEP and GNG_PEP flux were higher in obese subjects, and glycogenolysis contributed less to glucose production than in lean subjects. GNG_PEP flux correlated with all indexes of adiposity and with postabsorptive leucine rate of appearance (R_a) (protein catabolism). GNG_PEP was negatively related to the clamp glucose rate of disposal (R_d) and to the protein anabolic response to hyperinsulinemia. In conclusion, the increased contribution of GNG to glucose production in obesity is linked to increased postabsorptive protein catabolism and insulin resistance of both glucose and protein metabolism. Due to increased protein turnover rates, greater supply of gluconeogenic amino acids to the liver may trigger their preferential use over glycogen for glucose production.

Dementia is increasingly prevalent with age and negatively affects the quality of life of both patients and families.¹ Unfortunately, the pathological changes responsible for dementia appear to be irreversible by the time of diagnosis. Treatments are few, very limited in efficacy, and target symptoms.² Therefore, identifying modifiable biomarkers that may estimate the risk for subsequent cognitive decline is critical. Such measurable biomarkers could identify high-risk patients appropriate for further testing of potential disease-modifying therapies.

Background: Aging is associated with sarcopenia (low muscle mass) and dynapenia (low muscle strength) leading to disability and mortality. Widely used previous cut‐points for sarcopenia were established from dated, small, or pooled cohorts. We aimed to identify cut‐points of low strength as a determinant of impaired physical performance and cut‐points of low appendicular lean mass (ALM) as a predictor of low strength in a single, large, and contemporary cohort of community‐dwelling older adults and compare these criteria with others.Methods: Cross‐sectional analyses were conducted on baseline data from 4725 and 4363 community‐dwelling men and women (65–86 years, 96.8% Caucasian) of the Canadian longitudinal study on aging comprehensive cohort. Physical performance was evaluated from gait speed, timed up‐and‐go, chair rise, and balance tests; a weighted‐sum score was computed using factor analysis. Strength was measured by handgrip dynamometry; ALM, by dual‐energy X‐ray absorptiometry and ALM index (ALMI; kg/m²), was calculated. Classification and regression tree analyses determined optimal sex‐specific cut‐points of ALMI predicting low strength and of strength predicting impaired physical performance (score < 1.5 SD below the sex‐specific mean).Results: Modest associations were found between ALMI and strength and between strength and physical performance score in both sexes. ALMI was not an independent predictor of physical performance score. Cut‐points of <33.1 and <20.4 kg were found to define dynapenia in men and in women, respectively, corresponding to 21.5% and 24.0% prevalence rates. Sarcopenia cut‐points were <7.76 kg/m² in men and <5.72 kg/m² in women; prevalence rates of 21.7% and 13.7%. Overall, 8.3% of men and 5.5% of women had sarco‐dynapenia. Sarcopenic were older and had lower fat mass and body mass index (BMI) than non‐sarcopenic participants. While the agreement between current criteria and the updated European Working Group for Sarcopenia in Older Persons recommendations was fair, we found only slight agreement with the Foundation for the National Institute of Health sarcopenia project. Older persons identified with sarcopenia as per the Foundation for the National Institute of Health criteria (using ALM/BMI as the index) have higher BMI and fat mass compared with non‐sarcopenic and have normal ALMI as per our criteria.Conclusions: The proposed function‐derived cut‐points established from this single, large, and contemporary Canadian cohort should be used for the identification of sarcopenia and dynapenia in Caucasian older adults. We advise on using criteria based on ALMI in the diagnosis of sarcopenia. The modest agreement between sarcopenia and dynapenia denotes potential distinct health implications justifying to study both components separately.