Do Iodine supplements need to be taken during pregnancy?

Yes. Studies have shown that most women do not consume enough iodine during pregnancy and lactation (231.89 and 237.26 µg/day). Iodine deficiency is diagnosed when the Urinary iodine concentration (UIC) is less than 100 µg/L for adults, less than 150 µg/L for pregnant women, and less than 100 µg/L for lactating women. During pregnancy, iodine deficiency may endanger neurodevelopment and even the life of the fetus.

Uses of Iodine

Iodine is an essential trace element for humans. Its main function is as a component of thyroid hormones that control basal metabolism, growth, and development. The thyroid gland is an efficient collector of iodine. Most of the iodine in the thyroid gland is bound to thyroglobulin. The thyroid gland has a variety of protective mechanisms that maintain normal thyroid function despite large fluctuations in daily iodine intake. Thyroid hormones regulate many important biochemical reactions, including protein synthesis and enzyme activity, and are key determinants of metabolic activity.

What foods contain iodine?

Seaweed (such as kelp, nori, kombu, and wakame) is one of the best food sources of iodine. Other sources include: table salt, bread, yogurt, eggs, oysters, ice cream, shrimp, corn, and broccoli. In dietary supplements, iodine is usually in the form of potassium iodide or sodium iodide. Many multivitamin/mineral supplements contain iodine, usually in doses of 150 micrograms.

Daily intake of iodine

Different international agencies define daily iodine requirements differently, and the World Health Organization (WHO) and the European Food Safety Authority list daily iodine requirements for different groups (see Figure 1).

The effects of high or low iodine levels on human health

People who do not get enough iodine cannot produce adequate amounts of thyroid hormone. The increased demand during pregnancy is related to the mother's increased need for thyroid hormone and the transfer of thyroid hormone to the fetus to ensure normal development. In pregnant women, severe iodine deficiency can cause growth retardation, intellectual disability, and delayed sexual development, which can cause permanent damage to the fetus. Less severe iodine deficiency can result in below-average IQs in infants and children, and reduced ability to work and think clearly in adults. In addition, an enlarged thyroid gland is often a clear sign of iodine deficiency.

Of note, excessive iodine levels can also cause an enlarged thyroid gland. The upper limit of iodine intake (see Figure 2). High iodine intake can lead to thyroid inflammation and thyroid cancer. Ingestion of very large doses of iodine (e.g., several grams) can also cause burning in the mouth, throat, and stomach; fever; stomach pain; nausea; vomiting; diarrhea; weak pulse, and coma. Acute or chronic iodine overdose can occur with the use of a variety of common medications and food additives. Failure to escape iodine-induced suppression of organic production can lead to hypothyroidism, a symptom that is temporary and resolves after iodine exposure is stopped. Excess iodine can also lead to excessive synthesis and release of thyroid hormones, inducing autonomous thyroid function in iodine-deficient areas or iodine-induced hyperthyroidism in iodine-rich areas. The antiarrhythmic drug amiodarone is a benzofuran product with an extremely high iodine content that has been associated with hypo- or hyperthyroidism. In the presence of defects in the body's own protective mechanisms, excessive iodine intake can interfere with normal thyroid function.

References:

[1] LIU S, SHARP A, LANE S, et al. Low Iodine Nutrition Knowledge in Chinese Breastfeeding Women despite Adequate Iodine Status[J]. ACS Applied Energy Materials, 2024, 25 2. DOI:10.3390/nu16040491.

[2] NEDIĆ O. Iodine: Physiological importance and food sources[J]. eFood, 2023, 4 1. DOI:10.1002/efd2.63.

[3] E. KOUKKOU; K. M; N Roupas. Effect of excess iodine intake on thyroid on human health.[J]. Minerva medica, 2017, 108 2 1: 136-146. DOI:10.23736/S0026-4806.17.04923-0.

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