Optimizing protein intake in aging

Our current knowledge on the causes of sarcopenia is still fragmentary. The most evident factors of age-related muscle alterations comprise impairment in protein turnover rate, neurodegenerative processes, reduction in anabolic hormone production and action, dysregulation of cytokine secretions, changes in the response to inflammatory events, sedentary lifestyle and inadequate nutritional intakes. Indeed, nutrition, in particular low protein intakes, may participate in the loss of protein mass during aging. Consequently, numerous studies have focused on the possibility to counteract the age effect on muscle loss by changing the quantity but also the quality of ingested proteins, aiming to optimize protein intake and retention through an improvement in amino acid bioavailability for the muscle tissues.

It has long been recognized that numerous dietary parameters, such as the amount of dietary proteins, affect protein metabolism. Recently, new concepts have been developed by testing either different types of protein sources, proteins with various digestion rates, meals with pulse or spread protein-feeding patterns or amino acids with specific anabolic function. This is therefore a new area in which not only quantitative but also qualitative properties of dietary protein are considered as a strategy to limit body protein loss during aging.

Recent studies have reported sarcopenia to be preventable by using nutritional intervention, but more experimental and clinical evidence is needed to modify the current recommendation in daily protein intake. The new concepts currently developed must be validated using large epidemiological studies in the long term before being applied to the elderly population.