One of the many theories regarding the cause of sarcopenia, age-related loss of muscle mass and strength, is that impaired processing of the essential amino acid leucine is a significant cause. If this is the case, then leucine supplementation should help to some degree. Similar suggestions have been made for a few other aspects of aging - that we should assign a modest fraction of the blame to the typically lower protein intake observed in older people, as tissues find themselves lacking sufficient raw materials needed to maintain themselves. The study here suggests that this is not the case, or at least that the contribution of reduced protein intake is small in comparison to the other mechanisms of degenerative aging.
Regardless of whether an adult is young or old, male or female, their recommended dietary allowance (RDA) for protein is the same: 0.8g/kg/day. Many experts and national organizations recommend dietary protein intakes greater than the recommended allowance to maintain and promote muscle growth in older adults. However, few rigorous studies have evaluated whether higher protein intake among older adults provides meaningful benefit.
"It's amazing how little evidence there is around how much protein we need in our diet, especially the value of high-protein intake. Despite a lack of evidence, experts continue to recommend high-protein intake for older men. We wanted to test this rigorously and determine whether protein intake greater than the recommended dietary allowance is beneficial in increasing muscle mass, strength, and wellbeing."
The clinical trial, known as the Optimizing Protein Intake in Older Men (OPTIMen) Trial, was a randomized, placebo-controlled, double-blind, parallel group trial in which men aged 65 or older were randomized to receive a diet containing 0.8-g/kg/day protein and a placebo injection; 1.3-g/kg/day protein and a placebo injection; 0.8-g/kg/day protein and a weekly injection of testosterone; or 1.3-g/kg/day protein and a weekly injection of testosterone. All participants were given prepackaged meals with individualized protein and energy contents and supplements. Seventy-eight participants completed the six-month trial.
The team found that protein intake greater than the RDA had no significant effect on lean body mass, fat mass, muscle performance, physical function, fatigue or other well-being measures. "Our data highlight the need for re-evaluation of the protein recommended daily allowance in older adults, especially those with frailty and chronic disease."