In developed nations, which nutrients are most apt to be lacking in a child's diet?

I believe that in developed nations, the nutrients that are most lacking in a child's diet are the; calcium, iron and zinc. Zinc is needed for the activity of more than 100 different enzymes in the body and plays a role in the immune function. It aids in the maintenance of healthy immune function in kids and may reduce the frequency of mild upper respiratory tract infections. Calcium keeps the bones healthy and teeth thus supporting the skeletal structure and function. Iron is an important component of hemoglobin.