Iodine deficiency and the thyroid conditions related to it are a serious public health concern. Several studies published earlier this year suggest iodine deficiency is re-emerging. While about 40 percent of the world’s population is thought to be at risk of iodine deficiency,¹ residents of developed countries are increasingly found to be lacking this essential nutrient. 

Your body cannot produce iodine so you must get if from your diet. Iodine is necessary to make thyroid hormones, which control your metabolism and other vital functions. Because your thyroid hormones also support proper bone and brain development in utero and during infancy, the proper intake of iodine is critically important for pregnant women, nursing mothers and their babies.

What Is Iodine and Why Is It Important?

As mentioned, iodine is an essential element needed for the production of thyroid hormone. Because your body does not make iodine, you need to be intentional to ensure you obtain sufficient amounts of this nutrient on a daily basis. Although iodine can be sourced from the foods you eat or through a supplement, many people eating a standard American diet generally get enough iodine simply by using table salt. I’ll say more about salt later in the article.

When your body lacks sufficient iodine, it cannot make enough thyroid hormone. If your deficiency is severe, your thyroid may become enlarged, a condition also known as a goiter. Iodine deficiency can also cause hypothyroidism (low thyroid function). In some cases, lack of sufficient iodine can trigger intellectual disabilities and developmental problems in infants and children whose mothers were iodine deficient during pregnancy.²

According to the American Thyroid Association, iodine deficiency has also been linked to “increased difficulty with information processing, diminished fine motor skills, extreme fatigue, depression, weight gain and low basal body temperatures, among other things.”³

Studies Highlight Iodine Deficiency as an Emerging Problem in Developed Nations

A 2018 study published in the journal Nutrients⁴ involving 1,007 mothers who gave birth to 1,017 children (including 10 twin pairs; multiple births other than twins were excluded), suggests iodine deficiency is a significant public health issue in Norway. After collecting data multiple times during pregnancy, at birth and during four follow-up points until the babies reached age 18 months, the researchers concluded:

“[T]his study adds to the increasing evidence that pregnant women in Norway are iodine deficient and that the diet of pregnant women does not secure a sufficient iodine intake. There is an urgent need for public health strategies to secure adequate iodine nutrition among pregnant women in Norway.”

Another body of 2018 research, published in JAMA,⁵ implicated iodine deficiency as a factor associated with impaired fertility. The study included 467 American women who were trying to become pregnant during a four-year span. The researchers, who were associated with the National Institutes of Health, found:⁶

• Slightly more than 44 percent of the women had urinary iodine to creatinine ratios (UI/Cr) of less than 50 micrograms (mcg)/gram (g) 
• Women with UI/Cr ratios lower than 50 mcg/g had a 46 percent lower chance of becoming pregnant in any menstrual cycle compared to women with normal iodine levels or those suffering from a mild deficiency
• Those experiencing milder iodine deficiencies — between 50 and 99 mcg/g — also took longer to conceive than women with healthy iodine levels, although the difference wasn’t statistically significant 

An earlier study published in 2013⁷ found children of women with a UI/Cr ratio of less than 150 mcg/g during pregnancy were more likely to have lower scores on verbal IQ, reading accuracy and reading comprehension at age 8.