Re- read your post and you have your answer! I know it's hard to buck the family MD, but realize they get NO nutrition training.
Ok, maybe a couple hours at best...really. There is no harm in dropping a food group.
Print out some of the medical research study citations Mark gives in his posts and give them to your brother.
At the end of the day, it's YOU who is the one suffering, NOT your well meaning , but misguided brother. Do what works for YOU.