my understanding is that there is a greater risk of food intolerances and causing allergies if you introduce solids before 6 months. milk should be the main source of nutrition in babies under 1 year, food at this stage is just for 'experience', NOT nutritional value.(especially if bre@stfed, but still if formula fed...)
my dd one had solids at 5.5 months due to mis-information.
dd2 was around 9 months.