I've been suffering with bad stomach issues most of my life, which slowly got worse over the last couple of years. I had a negative blood test for coeliac, and previously thought that going gluten-free when you don't have coeliac disease was some kind of psuedoscientific health fad.
However, after doing a food diary I realised my symptoms correspond to days where I ate high levels of gluten. I reluctantly decided to cut gluten out for a week to see how I felt, after attempts at cutting dairy and high FODMAP fruits and veggies made no impact. Within a couple of days of glutting out gluten I was feeling so much better. I used to feel so tired and fatigued that I had started to have naps after work (despite only being in my 20s!), my brain would feel so foggy and confused in the evenings that I could barely push a shopping trolley around Tescos, and my entire life was dictated by my stomach issues as I'd be afraid of leaving the house in case I had a flare-up. It's been life-changing.