Increasing Dietary Protein Requirements in Elderly People for Optimal Muscle and Bone Health

TLDR

Osteoporosis and sarcopenia, common age‑related degenerative diseases that cause bone and muscle loss and morbidity, are linked to dietary protein, which may help maintain mass when intake exceeds the current RDA, though the elderly require higher amounts due to attenuated anabolic response, increased IGF, and enhanced calcium absorption, with short‑term studies supporting up to 1.6–1.8 g kg⁻¹ day⁻¹ but long‑term safety still unproven. The study aims to identify the optimal dietary protein level for older adults by using functional measures of protein adequacy and assessments of muscle protein synthesis and tissue maintenance. Future research will employ functional adequacy tests alongside muscle protein synthesis and muscle/bone tissue maintenance measurements to determine this optimal protein level. Evidence indicates that protein intakes above 0.8 g kg⁻¹ day⁻¹ benefit adults, and raising the RDA for older individuals to 1.0–1.2 g kg⁻¹ day⁻¹ preserves calcium metabolism and nitrogen balance without harming renal function, pending long‑term trials.

Abstract

Osteoporosis and sarcopenia are degenerative diseases frequently associated with aging. The loss of bone and muscle results in significant morbidity, so preventing or attenuating osteoporosis and sarcopenia is an important public health goal. Dietary protein is crucial for development of bone and muscle, and recent evidence suggests that increasing dietary protein above the current Recommended Dietary Allowance (RDA) may help maintain bone and muscle mass in older individuals. Several epidemiological and clinical studies point to a salutary effect of protein intakes above the current RDA (0.8 g/kg per day) for adults aged 19 and older. There is evidence that the anabolic response of muscle to dietary protein is attenuated in elderly people, and as a result, the amount of protein needed to achieve anabolism is greater. Dietary protein also increases circulating insulin-like growth factor, which has anabolic effects on muscle and bone. Furthermore, increasing dietary protein increases calcium absorption, which could be anabolic for bone. Available evidence supports a beneficial effect of short-term protein intakes up to 1.6 to 1.8 g/kg per day, although long-term studies are needed to show safety and efficacy. Future studies should employ functional measures indicative of protein adequacy, as well as measures of muscle protein synthesis and maintenance of muscle and bone tissue, to determine the optimal level of dietary protein. Given the available data, increasing the RDA for older individuals to 1.0 to 1.2 g/kg per day would maintain normal calcium metabolism and nitrogen balance without affecting renal function and may represent a compromise while longer-term protein supplement trials are pending.