Iodine is naturally present in water. Iodine was one of the first minerals to be recognized as vital for good health. It is still considered one of the most important elements in our body. In practically all countries, there are areas where iodine is lacking in the soil and water. Only one country - Japan - is virtually free from Goitre (an iodine deficiency diseases) and this is attributed to the relatively high consumption of seaweed as a foodstuff. Seaweed contains about thousand times as much iodine as any other food. It has been used in the Japanese diet for many generations without any apparent adverse effects. 

Iodine ends up in surface waters naturally through rains and water evaporation. Eventually, it also ends up in groundwater. Other options include weathering of iodine-containing rocks, and volcanic activity (including under-water volcanoes). In nature, iodine can be found in reasonably in large amounts, but only in compounds. Brown algae accumulate up to 0.45% (dry mass) of iodine. Corals, sea sponges, shells and fishes accumulate high iodine concentrations, usually in the shape of thyroxin or tri-iodine thyroxin.  

Iodine plays an important role in the production of thyroid hormones. The human body usually contains about 10-15 mg of this substance. The larger part can be found in the thyroid gland. The recommended daily intake for iodine is between 150 and 200 mg. Generally this dose is achieved by eating kitchen salt to which iodine is added. Iodine mainly affects the thyroid gland, which controls many important functions in the body. In fact, iodine is the single most important nutrient to the thyroid gland. Goiter, an enlargement of the thyroid, occurs when the thyroid doesn't have enough iodine. The thyroid gland is an iodine organ, producing powerful hormones needed throughout the rest of the body's organs. The hormones produced, regulate the metabolism of the body. The speed of all basic cell functions, called metabolism, depends on the thyroid. When the thyroid can't produce the iodine the body needs, many serious conditions may result. Some minor conditions are fatigue, weight gain, and bad circulation. Iodine protects the brain from toxins, and helps to neutralize toxins found in the rest of the body. The body has a much harder time warming itself when there is a deficiency in iodine. Iodine is also essential for children’s growth and development, and a deficiency in pregnant women is the primary cause of preventable mental retardation and brain damage.