There is no best time…
There are various theories in regard to when it is the best time to consume protein to maximise muscle protein synthesis (MPS) whether it should be before, after workout or before sleep. I personally prefer to have carb rich snack before workout and protein meal/shake after the training.
The post-exercise period is often considered critical, known as anabolic window – the time when amino acids are used most effectively to repair muscle tissues. However
Consuming protein within 1h after work out is critical if:
- you trained in a fasted state (by fasted state we refer to the situation when your body finishes digesting the food – it may take 3-6h and it really depends on the meal).
- you didn’t have any protein rich meal/snack/shake before training
- you trained for prolonged period of time or your training was intense and certain amino acids are needed to repair muscle tissues. By prolonged period of time we refer usually to training for more than >1.5h.
On the other hand If you consumed protein before training your body probably still has some amino acids in the pool to repair muscles hence refuelling straight after workout is not so urgently needed comparing to the training in a fasted state i.e
Resistance training stimulates MPS up to 72h, hence what really matters is regular protein intake spread out through the day.
Measuring MPS is quite complex and there are many studies with no clear evidence weather it’s purely timing or other factors contributing to maximising MPS like total protein intake, cortisol levels, intensity and type of the exercises, pre workout snacks/meals or even genetics!
Regardless of this we should keep in mind the more muscle is broken down the more amino acids you will need to repair muscle tissues and providing right amount of protein on daily basis is the key.
EN 
PL