Final answer:
Iron is the most common nutrient deficiency in young children globally, leading to anemia and affecting cognitive and motor development. It surpasses deficiencies in calcium, folate, and zinc, underscoring the importance of adequate iron intake.
Step-by-step explanation:
The most common nutrient deficiency in young children in the U.S. and around the world is inadequate iron consumption. Iron deficiency can lead to anemia, which is particularly prevalent among women and children under five years of age. Not only does anemia cause increased mortality in infancy, but can also contribute to detrimental cognitive and motor development in early childhood. These problems cannot be easily reversed and showcase how critical it is to ensure children receive sufficient iron in their diets. It's important to note that while deficiencies in other nutrients such as calcium, vitamin A, and iodine also pose significant health concerns, iron remains the most commonly deficient micronutrient worldwide. Recognizing and addressing iron deficiency is therefore crucial in preventing the adverse effects on health and development it can cause.