My partner has issues with gluten.
He constantly felt tired, anxious, his joints hurt, regular heart burn, digestive issues, etc. Him being a chef didnt give him much luxury to have control over his diet.
Once we moved in together, I suggested we start eliminating certain foods to see if it helps. The first one to go was lactose, which was easy as I am severely lactose intolerant, and had many lactose free foods at home anyway.
Then we removed gluten from his diet, (I knew a lot about gluten rich foods because my best friend here is allergic to it). In a couple of weeks things improved tremendously!
He ate gluten again just confirm our theory, and his stomach was awful again for 3-5 days. Since then he stopped eating gluten, although he does drink normal beer sometimes, which makes him mildly ill.