it has been proven that you increase the risk of your child having (possibly serious) allergies if you start solids before their gut's/immune system is old enough to cope, which is around 6 months roughly for all babies
i still think this is an important medically researched 'fact' (see the solids article on the bellybelly article section) - im not 100% convinced all GP's keep themselves up to date with this kind of info, they are not required too i dont think:P
same with the majority of CHN's im afraid