Is casein protein better for muscle than whey?

Short answer

No. After a single dose, fast-absorbing whey raised muscle building more. Over weeks of training, the gap between the two was about 0.3 kg. Hitting your daily protein mattered more than the type.

Is casein protein better for muscle than whey?
'Slow absorption → longer supply → more muscle' — does this formula hold?
People say casein digests slowly and feeds your muscles for longer, so it must be better. Both come from milk. We checked, step by step, whether casein really wins.
The two proteins absorb at different speeds
Whey is fast and short, casein is slow and long
Whey sent blood amino acids up fast and high, then they dropped quickly. Casein kept them gently raised for 7 hours. Whey raised whole-body protein building by 68% and casein by 31%, while only casein cut protein breakdown, by 34%.
After one dose, whey came out ahead
Muscle building after training was more than double casein's
18 people drank whey or casein with the same 10 g of essential amino acids after training. Muscle protein building with whey was about 122% higher than casein in the trained leg and about 93% higher in the resting leg. For a single dose, 'fast and high' beat 'slow and long'.
So what happens over weeks?
After 8 weeks, muscle gain showed no difference
16 people trained 4 times a week for 8 weeks and took 24 g of whey or casein before and after each session. Lean mass (muscle and everything except fat) rose 1.5 kg with whey and 1.4 kg with casein. Leg press max rose 88.7 kg and 90.0 kg. No difference.
Pooling 36 trials
Both worked, and the gap was 0.3 kg
An analysis that pooled 36 trials (1,552 people training with protein) found lean mass rose 1.24 kg more with whey and 0.92 kg more with casein than with a fake supplement. The gap is just over 0.3 kg. Another analysis of 4,711 people also found milk proteins, including whey and casein, raised both muscle and strength.
Only small trials showed big gaps
Trials of 13 and 38 people even pointed opposite ways
In a 10-week trial of 13 people, whey added 5.0 kg and casein 0.8 kg. In a 12-week diet trial of 38 people, it flipped: casein 4 kg, whey 2 kg. Single small trials swung widely. Pooled together, the gap shrank to 0.3 kg.
Bottom line: casein is not better
Your daily protein total comes before the type
After one dose, whey raised muscle building faster. Over weeks, the gap between them was about 0.3 kg. In the 36-trial analysis, whey's benefit stopped growing at 30-35 g a day. Pick whichever fits your budget, stomach and taste, and hit your daily protein.