We’ve got nothing against protein powder, but if it has ingredients from any food not allowed on your Challenge level, it will cost you a point. There are protein powders that are acceptable, like some egg protein powders. They must not, however, contain prohibited ingredients.
You may use whey protein on the LIFESTYLE and KICKSTART LEVELS, but not PERFORMANCE.
As Robb Wolf says, "Believe it or not protein powders are a processed food. Yes, you heard that correctly – these powders are far from a ‘natural phenomenon’. You cannot milk a cow and get a powder, city kids you’re just going to have to trust me on this one. So, where does the powder come from? In the case of whey, it’s often a waste product of cheese making and unless you’re getting the super pricey, meat is a better deal, protein powder from grass-fed animals you’re likely getting ‘grain-fed waste’. Let’s also consider the process that makes the whey into a powder (it’s liquid in real life…) – this process be it whey or egg white often utilizes extremely high heat (like higher than cooking). This ‘hot air’ denatures the protein to an extent that may increase its carcinogenic load. And hold on, there’s more!! Some of these powders even come with some bonus MSG!! Remember that rule about food that comes in a package, needs a label and can live on a shelf for an extended period of time? Apply that here."