You may be sleeping, but your muscles don’t have to!

As we age, our body composition begins to change, primarily through the loss^[1] of skeletal muscle and strength, leading to a decline in functional capabilities. This age-related decline in skeletal muscle mass is called sarcopenia^[2] and usually begins around age 40^[3] for both men and women. Sarcopenia poses a serious problem for older adults because a loss in skeletal muscle mass and function is associated with an increased risk for falls^[4] and mortality^[5].

A contributing factor to the development of sarcopenia is a reduced sensitivity of older adults to the anabolic stimulus of eating protein, termed “anabolic resistance^[6].” In other words, older adults need more protein to elicit the same growth-promoting effects observed in young adults. Some of the mechanisms contributing to anabolic resistance are shown in Figure 1. What these mechanisms may add up to is a need for more protein as one ages. For example, while 20 grams of whey protein maximally stimulates muscle protein synthesis (MPS) in young adults^[7], 35 grams is necessary for older adults^[8]. It has been proposed^[9] that the ideal dose of protein is roughly 0.25 grams of protein per kilogram of bodyweight (g/kg) per meal for young adults and 0.4 g/kg per meal for older adults.

Optimizing the protein content of meals in the elderly is obviously beneficial for preventing sarcopenia. However, elderly people are known to have reduced appetites^[10] that could limit overall protein intake during the day. Accordingly, the overnight ingestion of protein in elderly people has been studied before^[11] and suggested as an effective strategy for muscle protein synthesis. However, this previous investigation examining elderly participants in a hospital setting used a nasogastric tube, limiting its external validity. As such, the authors conducted a follow-up study that sought to evaluate the efficacy of presleep protein ingestion on overnight muscle protein synthesis rates in healthy older men.

Strength and muscle mass decrease with age due to a reduced sensitivity of muscle tissue to the anabolic stimulus of dietary protein. This is called sarcopenia. Supplementing with protein can help diminish the effects of aging on muscle mass and strength, but there are only so many meals eaten per day and reduced appetite might limit protein consumption. The authors of this study wanted to observe the effects of presleep protein on muscle protein synthesis.