My nutritionist called to see how I'm doing. An I have to say I'm feeling so much better than I did a week ago. She put me on a vitamin B supplement that has a kind of vitamin B2 (folate) that is particularly easy to adsorb.

Her hypothesis is that I don't absorb Vitamin B2 properly, which is governed by a gene. This has a knock-on effect that makes absorption of other minerals difficult.

I think I'll need to do some reading about this... I'll let you know what I find.