Associations between Hair Mineral Concentrations and Skeletal Muscle Mass in Korean Adults

Association between serum copper levels and muscle mass: results from NHANES 2011-2016

Copper is essential for various biological processes. However, excess copper has several adverse health effects. The effects of serum copper on muscle mass are poorly understood. This study aimed to investigate the association between serum copper levels and muscle mass in the US population. We utilized National Health and Nutrition Examination Survey (NHANES) data between 2011 and 2016 for analysis. Data on serum copper, muscle mass (measured using the appendicular skeletal muscle mass index (ASMI)), and covariates were extracted and analyzed. Weighted multivariate linear regression analyses and smooth curve fittings were performed to investigate the association between serum copper levels and ASMI. Subgroup analyses stratified according to age and sex were performed. In the presence of nonlinearity, threshold effect analysis was performed using a two-piecewise linear regression model. A total of 3860 participants were included in the final analysis. Serum copper levels were negatively associated with ASMI in the fully adjusted model. Furthermore, by comparing participants in the highest and lowest tertiles of serum copper levels, we found that the ASMI decreased by 0.292 kg/m2. In the sex-stratified subgroup analysis, we observed an inverse association between serum copper levels and the ASMI in both men and women. When stratified by age, the association remained significant among participants < 40 years of age, but not among those ≥ 40 years old. Smooth curve fitting revealed a nonlinear relationship between serum copper and ASMI, with an inflection point identified at 150.6 μg/dL. Our study revealed an inverse relationship between serum copper levels and muscle mass. This finding improves the current knowledge on the impact of serum copper on muscle loss and highlights the importance of serum copper homeostasis in muscle health.

Effect of dietary supplementation with multinutrient soy flour on body composition and cognitive function in elderly individuals at the risk of low protein: a randomized, double-blind, placebo-controlled study

Insufficient protein intake and cognitive decline are common in older adults; however, there have been few studies on low protein risk screening and complex nutrient interventions for elderly individuals in rural communities. This study aimed to evaluate the effect of dietary multinutrient soy flour (MNSF) on body composition and cognitive function in elderly individuals who are at risk of protein deficiency in a randomized, double-blind, placebo-controlled clinical trial. Nutritional interventions were given to those found to have low protein levels using bioelectrical impedance analysis (BIA). Among 733 older adults screened, 62 participants were included and randomly assigned into two groups, one taking soy flour and the other taking MNSF for 12 weeks. A previous cross-sectional survey found that 35.1% of the elderly people with an average age of 71.61 ± 5.94 years had an inadequate body protein mass proportion. After the intervention, the MNSF group demonstrated a significant improvement in protein mass, muscle mass, mineral levels, skeletal muscle mass, and fat-free mass compared with baseline (all P < 0.05), as well as a better upward trend compared with the soy flour group (P = 0.08; P = 0.07; P = 0.05; P = 0.08; P = 0.07). Regarding the mini-mental state examination (MMSE) scores, the MNSF group showed a significant decrease after 12 weeks (P < 0.05), which were significantly different compared with the soy flour group (P < 0.05). In the future, the application of MNSF as a food-based supplement to improve nutrition and delay cognitive decline in older adults at the risk of protein deficiency may be considered.