Re: It is not portion size which matters
There's also the issue of flour quality.
The wheat nowadays has been grown for quantity but not quality, there's more kernels of wheat (i think that's the right term) but the mineral profile is far lower. This is in part due to the cross breeding of different strains to optimise the quantity, and also partly due to overfarming depleting the minerals in the soil which the wheat would have historically passed on to us (this is also the reason that cattle have to be supplemented with b-vitamins)
If you want bread which is actually good for you, you have to make it yourself, but even then you can't use normal bread flour because it's still terrible quality. You're better off buying a home grain mill (or making your own) and milling your own flour straight from the grain. This way it's fresher and healthier as you know exactly what's gone in.
But then you still have the issue that a fair bit of the grains mineral makeup are actuallly various minerals that stop the absorption of other minerals, so a lot of the benifits can go straight through you, how to solve this? Sprout the grain first.
You can buy sprouted grain flour, but considering the process of sprouting the grain and grinding it up, I'd be wary of the freshness.
Also, sprouted grain breads taste... different. Just an FYI