Is whey protein harmful especially while doing p90x ?

Bloating, gas...: Obviously, don't be drinking it while doing p90x, but if you wanted to use whey protein supplement after workouts, that's fine. Just know that for many people, they can cause bloating, gas, and diarrhea. And the human body can only absorb so much protein per hour - with the commercial supplements, there's a lot of money - literally - going down the drain.

Moderation!!: Whey protein itself is not harmful, but as with most things too much of a good thing is bad. 1 gram per pound of body weight divided between your meals is the most i suggest taking and only in combination with a well rounded diet including carbs and fats from fresh veggies, fruits, fish, nuts, etc.

Remember: While whey protein isn't likely harmful, unless you are lactose intolerant or have a milk allergy, be mindful about your protein intake. Many people overdo it on the protein supplements and sometimes can negate the weight loss side of a training regimen when they utilize protein shakes/supplements with a significant number of calories.