DS is 13 months old and I have recently switched to cow's milk from formula. I still give him formula; I keep the ratio (50:50). I read a lot of things on the internet about formula having certain esssential nutrients like iron which cow's milk may not provide.

Any suggestions on this? DS is a little underweight and doesn't eat solid that well. Milk/Formula is still a major source of nourishment for him. When would it be good to switch to cow's milk completely.

Thanks