Protein intake has been identified as a key modifiable factor in preventing and managing sarcopenia, a common age-related condition characterized by the loss of muscle mass, strength, and function. This scoping review aimed to summarize the available literature on the association between protein intake and sarcopenia-related outcomes among Korean older adults and identify current research trends and gaps in this field. The review followed the 5-step methodological framework developed by Arksey and O’Malley for scoping reviews and adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews checklist to ensure a comprehensive search strategy. Protein intake was assessed using various methods, including grams per day, grams per kilogram of body weight per day, and intake quartiles. Sarcopenia-related outcomes were categorized into 3 domains as follows: muscle mass, strength, and physical performance. Although most intervention studies demonstrated improvements in muscle mass following protein supplementation, findings on muscle strength and physical function were inconsistent. Cross-sectional studies generally reported better sarcopenia-related outcomes with higher protein intake, particularly when the intake was expressed relative to body weight or analyzed according to quartiles. However, heterogeneity in protein intake assessments and variations in sarcopenia definitions could have contributed to the inconsistent findings across studies. This review highlights the need for applying standardized approaches for protein intake measurement and sarcopenia diagnosis. Future studies should consider the quantity, quality, and timing of protein intake while also focusing on the implementation of integrated, multidisciplinary intervention strategies to promote healthy aging among Korean older adults.
The health benefits of dietary fiber are widely recognized, but its impact on muscle health remains unclear. Therefore, this study aimed to elucidate the relationship between dietary fiber intake and muscle strength through a cross-sectional analysis of data from the Korea National Health and Examination Survey (KNHANES). Data from a single 24-h dietary recall and handgrip strength tests of 10,883 younger adults aged 19 to 64 years and 3,961 older adults aged ≥ 65 years were analyzed. Low muscle strength was defined as handgrip strength < 28 kg for men and < 18 kg for women. Multivariable linear and logistic regression analyses were conducted to determine the association of dietary fiber intake with muscle strength. Approximately 43% of Korean adults met the recommended intake of dietary fiber, and those with higher dietary fiber consumption also had higher total energy and protein intake. After adjusting for confounding variables, dietary fiber intake was found to be positively associated with maximal handgrip strength in younger women aged 19 to 64 years (β = 0.015; standard error [SE] = 0.006) and older men aged ≥ 65 years (β = 0.035; SE = 0.014). For older women aged ≥ 65 years, those in the lowest quartile of dietary fiber intake had a higher risk of low muscle strength than those in the highest quartile after adjustment of confounders (odds ratio 1.709; 95% confidence interval 1.130–2.585). These results suggest that adequate dietary fiber intake may reduce the risk of sarcopenia in older Korean women.
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