Maybe bullshit theory: there have been studies where they make sheep deficient in b-vitamins and then let them out on pasture. The results of these studies (which I read about second hand and haven't looked at myself. Might be bullshit science) is that the deficient sheep looks for b-vitamin I och foods like alfaalfa to much greater extent than a non-deficient control group.

I stopped eating fortified foods, changed my diet a bit and started getting cravings for leaf parsley and lentils.