Please state what foods and drinks he is eating and drinking so I am able to answer your question. Thank you.
If you are having problems with your 3 year old eating (as I was last year), you should try these new nutrition bars with a seed/grain called salba. I dont like most of the "nutrition" bars out there with the chocolate coatings and food coloring. But after a friend recommended them, I tried the salba bars and I was pleasantly surprised. They're really, really yummy and my son is practically addicted to them (not to mention me). Even better, they're loaded omega 3s, calcium, fiber, antioxidants, a little protein and they're sweetened with agave nectar, which is low glycemic so no sugar spike and crash. Good luck to you. I know it can be difficult having a picky eater.