The Significant Role of Micronutrients in Early Childhood Development: Linking Iron, Zinc, Iodine and DHA to Body–Brain–Behavior Outcomes

Early childhood is a critical developmental period characterized by rapid physical growth, accelerated brain maturation, and the establishment of cognitive and behavioral functions. Adequate nutrition during this period provides the foundation for optimal development by supplying essential nutrients required for cellular growth, neurological organization, immune function, and metabolic regulation. While macronutrients provide energy and structural components, micronutrients serve as biological regulators that influence multiple developmental pathways. Deficiencies of key micronutrients during early life may compromise physical growth, impair neurodevelopment, and negatively influence learning ability, emotional regulation, and behavioral outcomes. The Body–Brain–Behavior (3B) Axis provides an integrated framework for understanding how nutrition influences whole-child development. This approach recognizes that physical growth, brain maturation, and behavioral regulation are interconnected processes driven by common nutritional and biological pathways. Among essential micronutrients, iron, zinc, iodine, and docosahexaenoic acid (DHA) have emerged as critical contributors to early childhood development. Iron supports oxygen transport, mitochondrial energy production, DNA synthesis, myelination, and neurotransmitter metabolism, particularly dopamine pathways involved in attention, motivation, and learning. Zinc plays essential roles in cellular growth, immune regulation, neuronal communication, synaptic formation, and neuroplasticity. Iodine is required for thyroid hormone production, which regulates neuronal migration, brain growth, myelination, and synaptic development. DHA, a long-chain omega-3 fatty acid and major structural component of neuronal membranes, contributes to synapse formation, neural connectivity, visual development, memory, and cognitive function. Importantly, micronutrients do not act independently; rather, they function synergistically through interconnected biological pathways. Adequate availability of multiple micronutrients supports healthy growth, optimal brain architecture, and adaptive behavioral development, whereas deficiencies may create cascading effects across the Body–Brain–Behavior domains. This review discusses the biological mechanisms through which iron, zinc, iodine, and DHA influence early childhood development and highlights their importance in supporting physical growth, neurodevelopment, cognitive performance, and behavioral regulation. Understanding these relationships reinforces the importance of micronutrient-focused nutritional strategies during the first years of life to maximize developmental potential and support lifelong health outcomes.