Increased non-mercaptalbumin-1 ratio would thus demonstrate the presence of potential protein undernutrition in adult rats, as manifested only by a decreased gain in a specific type of skeletal muscle; non-mercaptalbumin-1 among total albumin ratio could be useful as a robust marker of protein nutritional status, contributing to prevention of protein undernutrition-related diseases such as frailty and sarcopenia. This evidence concerns the gene ALB and sarcopenia.