3. Selenium deficiency
Studies have shown, many who are diagnosed with iodine deficiency have shown selenium deficiency as well. The thyroid glands needs both iodine and selenium to produce enough thyroid hormones, but when you lack both or just one, your body has lowered thyroid hormone levels. Low selenium levels cause the thyroid gland to work harder to produce hormones. It's important to have both selenium and iodine to support thyroid health.
The Journal of Pediatrics stated, about one-third of pregnant women in the U.S. are iodine-deficient. That's a shocking number but it actually gets worse. At the time, it's been estimated that only about 15% of breastfeeding and pregnant women take iodine supplements. Iodine deficiency is associated with impaired brain function in infants, and stunted physical and mental growth.
Smoke like tobacco contains a compound named thiocyanate. Thiocyanate inhibits the uptake of iodine and may be responsible for the reduction of levels. Tobacco smoke has a negative effect on thyroid function and can also block hormone action. (6)
6. Low dietary iodine intake
In 2004 a University of Texas study found that between 1950 and 1999 calcium, protein, iron, vitamin C and other vitamins and minerals in crops have been becoming increasingly depleted. They concluded that soil depletion had increased by as much as 40%. (7)
Nutrients like iron, calcium or vitamins are naturally in the some foods. Iodine does not naturally occur in specific foods, instead iodine has to be present in the soil. Unfortunately trace minerals like iodine are almost never added to our soils today.