Whey powder consists of roundabout 7o percent of lactose aka milk sugar, the other 30 percent are lots of minerals and vitamins. If you suffer from lactose intolerance ... well, you know, be careful or better avoid it.
You can take it as often as you like, but please start slowly with small amounts and watch your body reactions. Whey powder can be bought via Ebay. The health effects of whey have been known since thousands of years but then this knowledge "has been disappeared" (wonder why and by whom?)