Unflavoured Whey Protein. It could be a coincedence, but i dunno as id never took 50 in one go before
I know that the branded whey proteins tend to have other "stuff" in them, that could lead to a bad stomach, but I've always found unflavoured whey to be very clean tasting and easy on the stomach.
What flavouring do people use with their shakes anyway? My long standing favourite is:
3 parts Innocent smoothie
1 part juice made from concentrate
and a little water.
I've always found that adding cocoa, just doesnt cut it for me. ProLab's NLarge2 tasted great, but I think their flavouring was a little more complex then just adding some cocoa or chocolate powder.