The gluten thing is confusing me - as it always seemed to be the bit of advice that was followed. People weaned at 4 months but waited until 6 months for gluten.
However they are saying that maybe it needs to be introduced before 6 months...not after 6 months - there is still a big difference of 24 weeks and 17 weeks. The EAT study I cannot get my head around.
One of the issues the authors raised was that perhaps some studies have shown that babies weaned after six months are at higher risk of allergies or whatever.
However this group of babies is quite specific if you think about it. Even people I know who religiously EBF for 6 months tend to introduced solids by 26 weeks. Waiting until after is slightly different. Some of the reasons weaning is delayed is high genetic allergy risk, issues with feeding, other illnesses etc - it is typically not a representative sample (I realise some people just choose to wait or some babies are not ready).
So if a baby has a high genetic risk of allergy you are likely to wait until after 6 months. Baby still has allergy. This does not mean that weaning later caused the allergy. It is likely that waiting longer reduced the effects of the allergy or perhaps introducing formula might have increased those effects. Waiting until 6 months will not wipe that risk of allergy out. You will never know what would have happened following other options - and allergies are not a yes/no situation but a continuum.
However...a simple correlational study or looking at two groups might conclude that those in the later weaning group had more allergies than those in the earlier weaning group. Unless the studies are accurately controlled for you cannot really pick these things out.
What we need is a randomised controlled trial but who is going to consent to that really? The EAT study kind of starts to look at this but again to me is biased because only certain people will sign up - perhaps those who were not that bothered about age of weaning or those who had severe allergy risks and just wanted to try anything.
So we are a bit stuck!