Neanderthals were pushed out of their hunting and gathering areas by humans clearing the land for growing grains.   Since early Celiac disease processes may have few or no overt symptoms, and considering life span was much shorter back then, Celiac disease may not have been so detrimental to their health.   Other indigenous peoples who developed without indigenous grains also have reactions to wheat, barley or rye.  

And the fistula theory is scary but interesting!;)) Will do some research and perhaps mention to my GP... thanks for both of your replies! Saying that... my urine is not bright yellow....

Hmm.. the large amounts of vitamin B could be a possibility. As I now eat huge amounts of white fish, c. 350g per serving and would have lots of Bs....

Thanks for your reply and yes, needless to say, I discontinued the supplements and also wrote to the companies! It was just yesterday that I ate a bit of Cheddar cheese and whoaaa... not good. It has 0 lactose / sugar so OK both lactose and fodmap wise... Thus am thinking Vitamin A... as I have read there can be between 120 and 225mcg in there.. Sadly in the UK is impossible to find a place to get tested and the NHS doesn't do these tests. Also followup endoscopies in the UK are done only every 5yrs! Same as smear tests. Shameful. But I am 50, diagnosed late,  so my gastroenterologist is checking for refractory celiac disease... In any case I will continue to consume fruit and veg with beta carotene but will hold off the dairy and oily fish which all have high levels of vitamin A. I will gradually reintroduce the fish at some point. Also I have another Clacium supplement now. The vitamin A toxicity can make your bones a he and eyes feel odd, which is what I had...

I just did a quick A.I. check, and vitamin A toxicity has never been associated with a bright yellow vaginal discharge.  Large amounts of B vitamin, aside from causing bright yellow urine, can occasionally cause a yellow tinged vaginal secretion.  I know that older women sometimes develop a fistula from their urethra to their vagina.  If this happened, I suppose a small amount of bright yellow urine could leak into the vagina, becoming a vaginal drainage.    SORRY MEN OUT THERE!  Read at your own risk!