just been reading who literature
in a nut shell
family foods pdf 1998 - bf alone for at least 4 months, weaning from 6 months unless baby is still hungry after feeds and/or not gaining weight adequately, from 4 months. never before as food displaces bm, increases risk of tummy upset as food isn't as clean as bm, less bm means less goodness, to much bulk fills up and replaces bm, mothers get pregnant when not bf exclusively
later publications, state that all the above reasons are why they now say from 6 months as waiting will not harm. Not that weaning from 4 months WILL harm. 1998 booklet is still the one they read from and is the original thinking behind todays guidelines
they also say that from 6 months, bm alone is NOT adequate nutritionally and complimentary foods NEED to be given
3-5 months - bm will have enough nutrients in most cases
6-8 months - the gap is around 200kcal
9-11 months - the gap is around 400kcals
12-23 months - the gap is around 800kcals
So not dangerous for from 4 months, just more risk of the runs (cos I can't spell diarear) and due to less breastfeeding takes away some of the antibody protection and there are some babies that will need feeding earlier. 6 months is not set in stone for bf babies
no mention of leaky/virgin gut
Their literature talks very little of ff babies and why they should be weaned, just says from 6 months in newer publications and that milk isn't adequate alone