Gourmet salts with appealing names like Himalayan Salt and Black Truffle Sea Salt have become increasingly popular in recent years. In addition to their unique look and flavor, these alternatives to the usual iodized table salt have been advertised to be a healthier dietary choice. But are they? The reason why it’s problematic to think gourmet salts are healthier is rooted in a health issue that drew national attention in the 1920s.
The story of iodized salt and human health can be seen in your own kitchen or in the spice aisle of the grocery store. If you pick up any salt container, you should see an inscription on the packaging mentioning the presence or absence of iodine (or iodide) (Fig. 1). While this text is often overlooked, including iodized salt in your diet is a simple and effective means to prevent iodine deficiency, a primary cause of goiters, hypothyroidism, and cretinism (severely stunted physical and mental growth). Because we cannot make our own iodine, humans are dependent on our food to obtain iodine. These medical realizations led to some 120 countries mandating salt iodization in all food grade salts. However, salt iodization is still voluntary in the United States .
Figure 1. Your salt should be labeled with whether it is iodized or not. Salt iodization is still voluntary in the United States. (Figure by Lian Guo)
Why is iodine so essential for proper mental development?
Iodine is essential in production of thyroid hormone in your thyroid (Fig. 2). Thyroid hormones are crucial in controlling energy production in your body, especially during the creation of new tissues during early development . In order to be functional, thyroid hormone must be iodinated, meaning three or four iodide atoms must be attached to the thyroid hormone structure. You can follow the creation of thyroid hormone in the diagram below to see how iodine is essential in this process. Now imagine, if there are low amounts of iodine in one’s system, thyroid hormones cannot be produced. As a result, that individual would develop hypothyroidism (low levels of thyroid hormone).
Figure 2. A) Your thyroid sits on either side of your larynx. If you develop hypo- or hyperthyroidism, this can cause your thyroid to swell into a “goiter.” (Figure is Public Domain)Link. B) Your thyroid is made of follicles that look like bubbles. This structure is essential for iodination of your thyroid hormones. (Image by Andrea Mazza - Own work, CC BY-SA 3.0, Link) C) The steps of thyroid hormone synthesis. Steps that require iodine are circled in red. (Figure by Mikael Häggström - Mainly Own workSource image for nucleus derivative:(Public Domain license), CC0, Link)
Becoming hypothyroid can negatively affect us at any age, but developing fetuses are extremely susceptible to hypothyroidism. Because thyroid hormone is so important for proper development of new tissues, poor brain development has repeatedly been an issue in babies of hypothyroid mothers. Once researchers linked iodine deficiency and hypothyroidism to impaired mental function, there was a push for universal screening of hypothyroidism in pregnant women, as well as the inclusion of iodine in prenatal supplements.
Is iodine deficiency still an issue?
Even though the health effects of iodine have been known for almost 100 years and improved agriculture has increased access to higher quality food, human populations around the world are still suffering from iodine deficiencies (Fig. 3). While there is typically more iodine deficiency in less developed countries, there are still cases of low iodine intake in areas where iodized salt is freely available .
Figure 3. Proportion of population and number of individuals in the population with insufficient iodine intake (1994-2006) and proportion of households using iodized salt. (Table by World Health Organization ).
With pressures to lower salt consumption (to avoid high blood pressure), increases in vegetarian/veganism (plants have lower iodine content than animals), and more consumers choosing non-iodized salts like sea salt, iodine deficiency may be on the rise again in the United States [1, 4]. The World Health Organization recommends a daily intake of 90 μg of iodine (~1/3 tsp iodized salt) for children <2 years old and 250 μg of iodine (~1 tsp iodized salt) for pregnant or lactating women. For more information on foods that have iodine, check out https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional/.
With the many different and often contrasting dietary recommendations we hear these days, it’s important to keep in mind how your dietary choices affect your biology. Even though gourmet salts have become popular gifts and household items, I encourage everyone to remember that iodized salt (or iodine-rich foods) is important in maintaining a healthy thyroid!
 Dasgupta, Purnendu K., Yining Liu, and Jason V. Dyke. “Iodine nutrition: iodine content of iodized salt in the United States.” Environmental science & technology 42.4 (2008): 1315-1323.
 Smith, Jeremy W., et al. “Thyroid hormones, brain function and cognition: a brief review.” Neuroscience & Biobehavioral Reviews 26.1 (2002): 45-60.
 World Health Organization. Assessment of iodine deficiency disorders and monitoring their elimination: a guide for programme managers. (2007). Third edition.
 Krajčovičová-Kudláčková, M., et al. “Iodine deficiency in vegetarians and vegans.” Annals of nutrition and metabolism 47.5 (2003): 183-185.
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