Micronutrients are essential components of the human diet, but dietary levels above or below their narrow, recommended range are harmful. Deficiencies increase the risk of stunted growth and metabolic, infectious, and respiratory disorders, and have likely been pervasive in human history, as local soils poor in micronutrients are widespread. Deficiencies are also common today, affecting approximately 2 billion people. Limited evidence exists for selenium, zinc, iodine, and iron deficiencies d...
