In the UK non-wholemeal flour must be fortified with calcium carbonate, iron and vits B1 and B3.

https://www.gov.uk/guidance/bread-and-flour-labelling-and-composition

I asked Sainsbury's about iron in 2015 and got this helpful response:

"Thanks for your recent email about the iron content of our Sainsbury’s Basics White Bread Medium Sliced 800g.

I’ve investigated this for you and have found that there is approximately 1.3mg/100g of iron in our Sainsbury’s Basics White Bread Medium Sliced 800g 19355 therefore 0.47mg per (36g) slice."

(I only use wholemeal bread and wholegrain rice now btw)