I'm afraid I'm really wary of soya now as well because my ds1 (mainly breastfed) was given some soya formula between about 8 and 10 months and developed an intolerance to it. Had bad advice from HV, GPs, dietitians because he was intolerant to cow's milk and they all said 'if he seems okay on the soya formula, carry on' but I now know that a very high proportion of dairy intolerant children are likely to develop an intolerance to soya if exposed to too much of it.
Also read the Observer magazine and it echoed an article in our NCT newsletter by a local nutritionist. To paraphrase her article, as well as the phyto-oestrogens mentioned by others, unfermented soya contains:
- enzyme blockers which can produce symptoms of gastric distress, deficiencies in amino acid absorption and lowered protein digestion;
- haemagglutinin, which can cause red blood cells to clump together (so they aren't doing their job very well);
- and higher levels of phytic acid than any other grain. Phytic acid is known to block the uptake of essential minerals such as calcium, magnesium and especially zinc in the gut.
(Fermented soya products, however, have lower levels of these 'antinutrients')
Sorry if this scares you , but this all seems to fit with my experience. We never had any problems with the volume of food that ds1 ate, but after he went off the soya formula (and similar products like soya cheese and yoghurts) ds1 put on loads of weight and was far healthier.
Incidentally, if you're using the soya milk because of suspected dairy intolerance, or if you just want to avoid creating a dairy intolerance, I would recommend a book by Jonathan Brostoff and Linda Gamlin called 'The complete guide to food allergies and intolerance' which has a section on food sensitivities in babies and children. It also flags up that children who appear to be free of symptoms of food sensitivity may find they have problems when they are older. I'm not a bf counsellor but agree with tiktok that GPs shouldn't be prescribing soya formula unless they have very good reason. Unfortunately many GPs don't know very much about food intolerances.
Hth and sorry if it's a bit strong but I'm speaking from bitter experience.