*3.3. Protein*

Two studies explored the effects of protein to improve sleep. Both studies used the whey protein isolate α-lactalbumin (dose range 20–40 g) [24,28]. In one study with healthy general populations, pre-sleep protein supplementation increased TST by 55 min, alongside a 7% increase in SE [28]. In the study by MacInnis et al. [24], α-lactalbumin had no effect on sleep variables in a small sample of cyclists (*n* = 6).
