Hi Eldar, it may take a little time for your dad to become accustomed to whey protein. He can also try taking hemp or rice protein as an alternative but a better idea might be to start with a very small amount of whey protein and build up over a few weeks. Everyone’s digestive track is different so it’s also important to try different proteins….take a look at my article of whey protein isolate vs concentrate

This supplement has helped me so much, but my dad’s stomach can’t take it and he ends up going to the bathroom multiple times a day. I was looking around the website and would like to know which one you would recommend he take in place of the whey protein.