When total daily protein intake is equated, there are no significant differences in muscle mass or strength gains between consuming protein before sleep and consuming it at other times of the day in resistance-trained individuals.

Study: Neither pre-sleep nor post-exercise protein consumption influences resistance exercise training adaptations in older adults

The study found that taking protein before bed didn’t help older adults gain more muscle or strength than taking it after workouts, as long as they ate enough protein overall. This matches the claim that timing doesn’t matter much.

Study: Daytime and nighttime casein supplements similarly increase muscle size and strength in response to resistance training earlier in the day: a preliminary investigation

The study found that taking protein before bed or during the day led to the same muscle and strength gains when total protein intake was the same. So, when you get your protein matters less than getting enough overall.

Study: Muscle-Related Effect of Whey Protein and Vitamin D3 Supplementation Provided before or after Bedtime in Males Undergoing Resistance Training

The study found that taking protein before bed or in the morning led to similar muscle gains, as long as the total amount was the same — which supports the idea that timing doesn’t matter much.

Study: Protein Supplementation after Exercise and before Sleep Does Not Further Augment Muscle Mass and Strength Gains during Resistance Exercise Training in Active Older Men.

The study gave some older men protein before bed after working out, and others got a fake supplement. After 12 weeks, both groups gained the same amount of muscle and strength, so timing protein before sleep didn’t help extra.