Just that really.
White bread has always bloated me but I've never been "poorly" with it and I was alright eating wholemeal bread, biscuits, pasta, pizza and other wheat based products so I put it down to white bread being more processed and having a lot of preservatives in. Now I get horrendous stomach cramps, wind, constipation and feel generally rubbish if I eat anything wheat based.
I've done an elimination diet and wheat is definitely a trigger. My B12 levels are normal (recent blood test for a well woman of a certain age health MOT thing).