In 1994 the World Health Assembly adopted a Resolution stating that complementary feeding should be fostered from about 6 months of age. Exclusive breastfeeding is recommended until 6 months of age, followed by continued breastfeeding with the introduction of complementary foods.
Yet here we are fifteen years later and you will see that the public health advice is routinely undermined by companies promoting complementary foods for use from 4 months of age or even less. The advantage for companies is that at a younger age, babies will need more processed food, like purés, than if allowed to start taking complementary foods at the age which is natural to them (baby-led weaning is a concept that is growing in popularity).
And if companies can entice parents to use their purés, then they gradually move them along the supermarket shelf to the foods labelled for older babies. Allow babies to taking solids when they are ready at six months of age and they can eat home prepared foods alongside the family (subject to some care over salt levels, for example). Six months is not set in concrete - it is a general recommendation.
The evidence base for the health benefits (as well as cost savings) of not introducing complementary foods too early has grown steadily. Today, Alyn Smith, a Member of the European Parliament for the Scottish National Party has announced his is taking up the case is Europe. The article posted on the SNP site explains why and what he aims to achieve at: