Perspective: Protein Requirements and Optimal Intakes in Aging: Are We Ready to Recommend More Than the Recommended Daily Allowance?

Abstract

The Dietary Reference Intakes set the protein RDA for persons >19 y of age at 0.8 g protein ⋅ kg body weight-1 ⋅ d-1. A growing body of evidence suggests, however, that the protein RDA may be inadequate for older individuals. The evidence for recommending a protein intake greater than the RDA comes from a variety of metabolic approaches. Methodologies centered on skeletal muscle are of paramount importance given the age-related decline in skeletal muscle mass and function (sarcopenia) and the degree to which dietary protein could mitigate these declines. In addition to evidence from short-term experimental trials, observational data show that higher protein intakes are associated with greater muscle mass and, more importantly, better muscle function with aging. We are in dire need of more evidence from longer-term intervention trials showing the efficacy of protein intakes that are higher than the RDA in older persons to support skeletal muscle health. We propose that it should be recommended that older individuals consume ≥1.2 g protein · kg-1 · d-1 and that there should be an emphasis on the intake of the amino acid leucine, which plays a central role in stimulating skeletal muscle anabolism. Critically, the often-cited potential negative effects of consuming higher protein intakes on renal and bone health are without a scientific foundation in humans.

Effects of high-velocity resistance training and creatine supplementation in untrained healthy aging males

“…For example, three previous meta-analyses showed that creatine supplementation during resistance training increased whole-body lean tissue mass, as assessed by dualenergy X-ray absorptiometry, air-displacement plethysmography, or hydrostatic weighing, in aging adults compared to placebo Chilibeck et al, 2017;Devries and Phillips, 2014 Furthermore, 3-day food records showed that males in the creatine group were only consuming ~ 1.0 g/kg of protein/day. Several reviews suggest that aging adults require ≥ 1.2 g/kg of protein/day to maintain/increase muscle mass (Morton et al, 2018;Phillips et al, 2016;Traylor et al, 2018). Therefore, it is possible that the sub-optimal daily protein intake attenuated the muscle hypertrophic response to creatine over time.…”

Protein supplementation improves lean body mass in physically active older adults: a randomized placebo‐controlled trial

“…The enhanced protein intake did not seem to affect renal function throughout the supplementation period because no differences in eGFR were observed compared with the placebo group and no changes in urinary albumin/urinary creatinine ratio were seen over time. Therefore, enhancing protein intake is not only effective but also a safe strategy to attenuate the age‐related loss of muscle mass in physically active older adults.…”

Myopathies Related to Glycogen Metabolism Disorders

“…Collectively, the data would suggest that GSD myopathy patients consume at least 1.2 g protein/kg/day to maintain muscle mass, especially with aging [117]; however, high intakes of greater than 1.6 g/kg/day cannot currently be recommended given that this level is the maximal one for stimulation of protein synthesis even for athletes performing heavy training [112]. Given that the oxidation of free fatty acids is an important compensatory mechanism in patients with GSD V [118,119](and presumably other myopathic GSDs), there has been interest in the use of a ketogenic diet by some patients who have anecdotally reported a significant reduction in GSD-associated symptoms and increased exercise capacity [120].…”