It is well known that thyroid hormones are very important for normal brain development. Iodine deficiency can lead to impaired thyroid hormone production, causing hypothyroidism in infants and children. As a result, infants and children are at increased risk of developing mental disorders. Even in mild cases of hypothyroidism, abnormal cognitive development can still occur. In the past, we usually used iodized salt for iodine supplementation, which has reduced or largely eliminated iodine deficiency, but in recent years, the incidence of iodine deficiency has gradually increased again. The National Health and Nutrition Examination Survey has tested the iodine content in urine. It was found that iodine deficiency was very common, with at least about one third of pregnant women suffering from mild iodine deficiency. The perchlorate molecule is very similar in shape to the iodine molecule and transports iodine or other anions through the sodium-iodine transporter to the thyroid follicular cells or to breast milk, where there is a competitive effect between the two when absorbed by the body, thus causing iodine deficiency. Nitrites can be found in well water and interfere with iodine metabolism in the body, so breastfeeding women should avoid excessive nitrite intake. The American Academy of Pediatrics recommends that all well water be tested annually for nitrate levels to prevent this from occurring. Smoking can produce thiocyanates, which have a competitive effect with iodine. Smoking ban and avoidance of second-hand smoke is another effective measure to prevent iodine deficiency. Therefore, perchlorates, nitrates, thiocyanates, etc. can have a competitive effect with iodine in the thyroid gland and in breast milk, aggravating iodine deficiency. In addition, the increased consumption of processed foods (mostly non-iodized salt) in the United States, the failure of pregnant or breastfeeding women to take adequate amounts of iodine supplements, and the failure of most supplements to be accurately labeled are also important causes of iodine deficiency. In fact, it is difficult to obtain the necessary amount of iodine through diet alone. Also, the inability to clearly label the iodine content of foods makes it more challenging to accurately assess iodine levels. It is recommended that women who are pregnant or breastfeeding should avoid environmental exposures such as nitrates in well water and thiocyanates from smoking, in addition to adequate iodine supplementation. We should incorporate iodine supplementation behaviors into our lives, such as taking oral iodine supplements, consuming iodized salt, ensuring that the well water used passes nitrite testing, and quitting smoking. Also, pediatricians, medical caregivers for pregnant women, women preparing for pregnancy or breastfeeding, and even internal medicine physicians should take the issue more seriously. The American Academy of Pediatrics encourages the use of iodine supplements to get enough iodine. At the same time, health care providers should encourage pregnant or breastfeeding women to use iodized salt whenever possible, support environmental agencies in regulating perchlorate levels in water, and recommend that the U.S. Food and Drug Administration (FDA) correct inadequate iodine levels and inaccurate labeling in iodine supplements.