Protein can and should be taken during Phase 1 and 3 of the program (Phase 2 is a zero protein day). It is more critical to take it during Phase 3 as your body will be craving protein from the zero protein day – it is much easier to get high amounts of protein in supplement form.
To take full advantage of the effect of the protein starvation day, you can try Protein Loading on the first day of Phase 3. Protein Loading is simple – take one scoop of protein every two hours on the hour while you are awake (aside from mealtimes and training times). If your protein powder gives you 20 grams per scoop, this could mean as
much as 160 grams of extra protein or more! At this point in the Phases your body will be sucking up and storing every available gram of protein you give it. This will help to maximize the effectiveness.
Protein Loading need only be done on the first day of Phase 3 but keep a regular, high-end intake over the course of the entire Phase. Here is a list of the when, why and how of effective protein supplementation, ranked in order of importance.