Should I drink protein powder or no?

15 male 5'11 150lbs.... Im trying to gain mass in my muscles. Ive come a long way since I have gained 20 pounds this school year by working out with p90x and insanity while drinking whey protein powder. People tell me that powder does not eve work and that I can get the same amount of protein by eating nuts and meats. What do you guys think? I have been out of working out for about a month due to recovery from the hospital and personal injury caused by working out.... Should I go back to the powders or stick to nuts/meats and occasionally protein bars?