Oops finger trouble - teach me to MN at work :(
Anyway, after reading that US report and a few bits around it I think the best advice - based on the actual known data anyway - should be something like this in the West:
- BF out to 4 months has huge health benefits.
- BF out to 6 months still has significant benefits but latest research is also showing purely BF is less beneficial than supplementing with solid food
- After that diminishing return start to kick in far more, as once a child is eating solid food, walking etc there are a whole load of other, bigger considerations for health and welfare than how the child gets milk.
The WHO advice is aimed at developing countries as well, where pure water and good food are not as easy to come by, so BF is a safer option for longer, until the child's digestive system can cope. But in the West going onto FF after a few weeks is not a huge risk owing to pure water, large scale inoculations, easy access to safe food etc etc.
I also read up around the social benefits - there too things are not as clear cut as often presented. There seems to be quite a lot of dispute about IQ and psychological benefits, the concerns being that EBF parents are likely to be caring parents anyway and thus stimulating and bonding with their child, and the EBF demographic in the Western studies may confer genetic IQ bias.
Btw the average age of BF ending being 4 worldwide is a made up number, averaging the theoretical age of human BF ending compared with a number of factors with other apes and monkeys, no one supports that seriously in any research.
So what the data is actually pointing to, for a Western country is up to 4 months of BF definitely helps a lot (but it's not an absolute necessity), solid foods + BF till 6 is still better, and do what you want after that, there are far bigger issues to deal with by then.
Oddly enough that was about the same advice as when I had mine in the 90's, and pretty much what the BBC program concluded as well.