Can Protein Powder cause diarrhea?

Whey protein powder can cause diarrhea in some people that are lactose intolerant. Lactose intolerance can also cause bloating, stomach cramps, gas and headaches. If you suffer any of these side effects after using whey protein powder you can switch to a non-dairy alternative such as a plant based protein or a whey protein isolate which generally have no lactose content.