Iodine is required for mammalian life, being an essential nutrient for at least two important metabolic functions, but rare in earth and water. First, the biosynthesis of the thyroid hormones, T3 and T4 controlling homeostasis, and second, the biosynthesis of hypoiodous acid (HOI), a powerful antimicrobial excreted in bodily fluids: milk, tears, saliva, and nasal, bronchial, and lung mucus. Typical protein sources of iodine are fish and squid, and excellent vegetable sources of iodine are kelp and seaweed; sea salt is very poor in iodine. Because oceanic food sources, fortified foods, and iodized salts are necessary for adequate intake, about 2 billion people are currently iodine deficient, a major, preventable catastrophe. Conditions exhibited by people suffering insufficient iodine intake are birth defects, cretinism, goiter, seriously depressed immunity, and eventually death, while excessive intake is rarely reported. The UK RDI and US RDA (150 μg/day), while set to avoid goiter, are too low to optimize immunity and prevent infections from many airborne microbes. The daily intake for Japan of 1–3 mg contributed to a very low death rate during the COVID-19 and H1N1 pandemics. We review the efforts, or lack thereof, of many governments to provide adequate nutritional iodine, of special importance for pregnant women and lactating mothers.