Is there an age when a breastfed baby "needs" to be eating solid food to receive proper nutrition?

Not solid food: but rather other foods at age 6 months, as mashed potatoes, fruits and other vegetables just to supply iron and other essential vitamins and minerals which are deficient in breast milk, but supplied in artificial cow milk formula

Culturally driven: There are some aboriginal cultures that totally BF to age 2 .This is probably a good idea where safe water is rare. But these kids are often quite picky and resistant to new items. Studies show the benefits of BF begin to fade some by 8-9 mo, and our culture drives us to get the kid to the table when they can sit well. It is hard to maintain proper iron intake without some solids by that time.