My father is in remission from bladder cancer. he gets checked regularly and blood work is good. Recently he thought that he had food poisoning and waited until very week before going in. They foung no cause. He lost alot of weight and is down to 128 pounds. I want to know if protein drinks, powder protein mixes or protein bars are O.K. for him to take. He needs to gain weight. What can he do? Please Help.