A.W.
Sounds like it could be celiac disease, sometimes called celiac sprue. It's an intolerance (allergy) to gluten: wheat, barley, rye, etc. Since these products are in so many things, every meal could set it off. There is a wealth of information available on the internet if you google celiac sprue, or gluten intolerance. Check his symptoms there.
I can't believe his doctor would want him to go through that every day. Might want to consider a new doctor.
Take care,
Ali