I have suggested it but think it is on deaf ears as he was also diagnosed with non-hodgkins lymphoma mantel cell about 3 years ago (in remission right now)but they say it is most likely to recurr with this type. I mentioned to he and my mother to be tested for celiac because of the relation between non-hodgkins and also B-12 and he also just recently (as well as my mother recently)was found to be vitamin D deficient. He is a very stubborn person and it is very difficult to get him to listen to anyone. Just last week he had sudden terrible stomach pains and was very constipated and tried to relieve the constipation with a vegetable laxative and an enema and the next morning was still in horrible pain. He went to his GP and the GP sent him straight to the emergency room because he thought my father had a possible bowel obstruction. At the emergency room they thought the same thing and sent him immediately for a CT scan. They were totally shocked to find out he actually had an acute ruptured appendictis and if he had not gotten to the hospital when he did they said he probably would have died very soon. Soooo scary. I had mine out at 18 and they said mine was close to rupturing.
I would suggest that you urge your father to get tested for celiac.
I hope he will reconsider the test for celiac but I don't really think he will.
Thanks for the suggestion.