Here’s a good study/article on Protein and the Elderly (Adv Nutr. 2014 Sep; 5(5): 599S–607S. Published online 2014 Sep 1. doi: 10.3945/an.113.005405
PMCID: PMC4188243. Keeping Older Muscle “Young” through Dietary Protein and Physical Activity. Daniel R. Moore*). One of the points
…35 g (∼0.45 g/kg) of whey protein stimulates mixed muscle protein synthesis in older adults, whereas 10 and 20 g (∼0.13 and ∼0.28 g/kg, respectively) do not.
Individuals who more frequently elicit a maximal stimulation of muscle protein synthesis throughout a daily meal feeding cycle would be more likely to maintain muscle mass and possibly function. This could explain in part the greater retention of lean body mass in older adults who consume more than the current RDA for protein [i.e., ≥1.2 g/(kg ⋅ d)] relative to those who habitually consume a suboptimal amount [i.e., <0.8 g/(kg ⋅ d)]