see, i think there's an interesting argument to be had about processed vs organic wholefood wrt this subject. are you better off giving your 4-month-old child some lovely organic carrot or putting them onto a processed food, ie formula? this is particularly pertinent, i always think, to mothers stopping bfing at around 4 months. should they go onto food with formula (less processed option) or just straight formula (more processed).
there is a bit of research which might be relevant, if you see welliemum around give her a shout will you, and tell her i was looking for her. i can't remember what it was, but she knows it.