Does a 40 g casein shake before bed secretly sabotage your sleep? A randomized, double-blind crossover trial in 21 NCAA Division I female athletes tracked sleep with WHOOP 4.0 bands and found no hit to sleep time, efficiency, resting heart rate or HRV. Alpha-lactalbumin and carbohydrate performed the same. But there's a twist: none of them improved sleep either. Here's what the data show, where the study falls short, and who should still skip the late-night shake.
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