This comes up all the time, so I’m putting it here so I don’t have to keep typing it. The questions are, “When should we start solids?” and “What should we use as first foods?” and “Why not wait longer than 6 months to start (or conversely, why wait past 4 months to start solids?)
There’s quite a bit of research (and a lot of parental experience with grabby babies) that says there is a “sweet spot” around six months for starting experimenting with solids. Babies started later than six months or earlier than four statistically speaking tend to have more allergies and reactions. Too early and the gut is still quite permeable and immune reactions can be triggered, too much later and they don’t get the small exposures that teach the immune system to ignore food as not-a-problem. Theoretically.
But this is not going to be a line by line cited official paper, this is how I feed my kids, and an approach to eating for babies that I think makes a lot of sense. I’ve been parenting for 21 years, have three children of vastly varying dietary foibles, allergies, sensitivities and pickiness, age 3, almost 10 and 21 1/2 at this writing, and have a zillion food issues so tend to read constantly on the subject. This is drawn from many sources, so if the wording appears familiar, it’s because I burned it into my brain at some point and don’t remember where I got it. I’m not looking up a darned thing for this right now, it’s mostly “what I tell people when they ask about it online”.