I'm pretty sure you can consume protein powder while breastfeeding. I know with my wife, we are going to try and find some better (probably expensive ugh) all natural protein powders when she is pregnant and breastfeeding. The only thing I wouldn't recommend is taking protein powders for weight loss or mass building, since those also contain additives and/or extra supplements like fat burners and such. I found some info on another site...not sure if I can post it here, so PM me if you'd like the link...