Serum albumin redox state as an indicator of dietary protein intake among community-dwelling older adults

Background and aims: Serum markers capable of detecting mild levels of undernutrition, such as insufficient dietary protein intake (IDPI), have not been established among community-dwelling older adults. Although the serum albumin redox state, expressed as the ratio of reduced albumin (Alb) to total Alb (the reduced albumin ratio), has the potential to overcome this challenge, empirical epidemiological data are lacking. This study aimed to investigate the association between a serum reduced Alb ratio and dietary protein intake among community-dwelling older adults. Methods: This study analyzed cross-sectional data from 1,005 community dwelling population (572 males and 433 females) aged 70-84 years who participated in the Itabashi Longitudinal Study on Aging. Exclusion criteria included participants with incomplete data, individuals with a history of kidney disease and high C-reactive protein (CRP) levels. The dietary protein intake was estimated using validated food frequency questionnaires. The IDPI was defined as not meeting the level recommended by the Dietary Reference Intakes for Japanese (Men >= 60 g/day, Women >= 50 g/day). Results: IDPI was observed in 14.1% of the study population. Logistic regression analyses adjusted for sex, age, body weight and malnutrition showed that a serum reduced Alb ratio was significantly associated with IDPI (odds ratio = 0.962, 95% confidence interval = 0.926-0.999), whereas serum albumin concentration was not (odds ratio = 0.549, 95% confidence interval = 0.285-1.061). Conclusions: A serum reduced Alb ratio would be a useful indicator of protein insufficiency among community-dwelling older adults. (c) 2024 European Society for Clinical Nutrition and Metabolism. Published by Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.