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Food Science for Good: There’s more to Iodine than meets the eye

Jen Hatz MS, RD, CSSD, LDN

Whether or not you’re already familiar with the story behind iodized salt, just wait because there’s more to the story than meets the eye. As of 2024, we’ve hit the 100 year anniversary of the introduction of iodized salt in the US as the first fortified food, of which was adopted to help combat the high prevalence of goiter, an overgrowth of the thyroid gland, where research findings at that time linked iodine deficiency with goiter. Goiter was a population-wide health concern at the time, especially in the northern US, primarily due to changes in diet and lifestyle for residents of that region being naturally low in iodine sources like fish and seafood, and instead high in protein sources derived from iodine-poor soil. 

In this case, there was a population-wide change in diet and lifestyle and therefore health and nutritional status based on geographic location, including limited availability or access to certain foods or nutrients, impacting their health in a similar manner.

With rates of goiter at an unprecedented high, and the knowledge at the time through research linking goiter to iodine deficiency, there was therefore the introduction of a fortified food as iodized salt adopted as the solution to provide this essential nutrient to those who are otherwise lacking or insufficient in it. By providing a necessary nutrient through fortified food, and especially in the form of a common ingredient or flavoring, this requires no major changes in diet and lifestyle, and no financial commitment or burden placed on the population, but rather a quick decision at the store to purchase the iodized salt rather than the other salt. 

This method proved successful as rates of iodine sufficiency increased and rates of goiter decreased through this simple adoption of a fortified food, which can now be deemed a successful solution for this public health concern. 

This alone is a big win for the field of food science and shows how the strategic planning for integrating food fortification into the food industry and across public or consumer purchasing patterns can ensure that adequate and necessary nutrition is easily achieved for those who need it most without excessive need for funding and implementation of changes in the lives and lifestyles of the population. 

This is a key consideration as we will forever battle with changes in our health, be it nutritional status or physical or mental health changes, in response to changes in our lives, lifestyles, and the environment around us impacting our own internal environment. So thoughtful food science is a plus!

Now here’s where the story gets really interesting:

It wasn’t just wide scale improvements in goiter that were observed with the change in iodine status, but population IQ improved by an average of 15 points in the quarter of the population that was most iodine deficient and with similar improvements in IQ across regions where iodine deficiency was the most prominent and where iodized salt was most prevalent. (1) This initiated a wave of global efforts to support supplementing this important nutrient across global health initiatives like through WHO, UNICEF, and the Iodine Global Network. (1)

To this day:

Iodine deficiency impacts two billion people worldwide and is the leading cause of preventable intellectual and developmental disabilities, even in mild or moderate iodine deficiency.(2) 

Even despite the progress in the US to combat iodine insufficiency over several decades through the use of iodized salt, the last 15 years have shown a resurgence of iodine deficiency once again, and this time in the most likely and most vulnerable populations of women in pregnancy. 

The impact of iodine on cognitive development starts early with an important role in thyroid hormone synthesis, regulating metabolic rate, energy production, and neural development.(2)  Low concentrations can adversely affect fetal brain development, and thus child and adult cognitive function.(2) Thyroid hormone activity increases in pregnancy, especially up to 20 weeks gestation, coupled with increased urinary iodine excretion, making it critical for pregnant women to consume sufficient iodine during pregnancy.(2)

Research shows inadequate iodine in pregnancy, as below the EAR (160 ug/d), associated with language delay, impaired fine motor skills and mental health problems at three years old. (2) 

What can we do about this?

If you’re thinking “what if we just make sure pregnant women have access to iodized salt” the answer is no, not quite. Here’s why:

This widespread iodine insufficiency is related to livelihood and lifestyles including:

  • Locations of populations

  • Insufficient knowledge of these problems

  • Insufficient knowledge of/access to solutions 

This is across demographics where access, availability, or selection of appropriate foods to meet nutrient needs may be impaired or impacted.

This includes decreased seafood consumption, often from replacing seafood in the diet with more land-based animal protein sources like chicken and beef. This can also include lack of knowledge, or access or availability of iodine rich food sources, lack of knowledge of the benefits of iodized salt, and overall intakes to aim for. The best natural source of iodine is seawater fish and seafood, followed by eggs and fresh dairy (3). Iodized salt has been the most important source worldwide as a strategy for achieving iodine sufficiency, however due to changes in dietary patterns, especially in the US over the last few decades, may need to be taken with a grain of salt, and adequately factored into individual and population needs safely and appropriately (3). 

Despite iodized salt providing a useful and easy-to-follow method for supplementing the diet with iodine, it can also lead to negative outcomes such as thyroid-related deaths if those who are chronically iodine deficient increase their iodine intake and concentrations too quickly. (1) 

Much like everything, more is not always better, but rather the right amount and the right guidance are. In addition to a thoughtful food science approach, we also need to be mindful about diet and lifestyle changes for demographics and education or consulting available for sound guidance across individuals.

We therefore should not prescribe general recommendations for everyone to simply increase their salt intake nor for everyone to blindly increase their iodine intake, but rather to seek out individualized approaches to best suit the needs per individuals across geographic locations and within their available resources. 

Why this can be a problem if it goes unnoticed:

Due to the high prevalence of sodium in the diet from a variety of foods and food products, recommendations to add iodized salt to the diet or to rely on iodized salt to meet our full iodine requirements may not be advisable for all populations, particularly during pregnancy and lactation when iodine requirements increase. This is especially relevant for those already at-risk for hypertension and heart disease, and specifically at risk for preeclampsia where Black women are at a statistically higher risk for complications during pregnancy. (4)

Study findings show that specifically US-born Black women compared to women born from non-US locations even when matched for racial identity, weight, smoking, stress, and more exhibited higher risks for preeclampsia and cardiovascular risk factors with birth-related complications, alluding to a need to take particular focus on potential interactions of confounding and overarching variables specific to US resources, social support, systemic trauma, and demographic disparities across income, education, and equitable healthcare access.(4) This places an added need for individualized approaches to meet health and nutrient needs across our communities beyond solely public health recommendations.

Government funded programs like WIC are offered with the purpose and intent of providing this level of health and nutrition guidance and solutions during pregnancy through lactation and early childhood development. Of those who qualify to receive these benefits, a majority do not utilize them largely due to insufficient knowledge and awareness of the benefits offered, their eligibility, and the solutions provided for problems otherwise at risk.(5)

 Spreading this information and increasing awareness is the problem and the solution. Otherwise this government funded program goes unutilized and risks being under scrutiny for cutting resources. This goes with equal importance to utilizing all government-funded programs related to food access and community nutrition initiatives like the school breakfast and lunch programs, summer food programs, SNAP, and more. (5) These programs offer ways to supplement the nutrition needs for all eligible individuals across our communities, and should be approached as our guide helping us towards optimal outcomes across our families and communities.

 Meeting iodine requirements is necessary for our metabolic and cognitive function, and doing so in the safest manner possible may take us back to the beginning where it all began, by creating more consistency in our food choices by incorporating more fish and seafood, eggs, and fresh dairy into our diets. Allowing for the innovative solution of iodized salt to act as a supplement to our dietary intake when appropriate, and maintaining a healthy and individualized approach to overall health and nutritional status with clear assessments and guidance from a Registered Dietitian who is well versed in equitable and impactful decisions across populations.

  1. Feyrer, J., Politi, D., & Weil, D. N. (2017). The Cognitive Effects of Micronutrient Deficiency: Evidence from Salt Iodization in the United States. Journal of the European Economic Association, 15(2), 355–387. 

  1. Bailote HB, Linhares D, Carvalho C, Prazeres S, Rodrigues AS, Garcia P. Iodine Intake and Related Cognitive Function Impairments in Elementary Schoolchildren. Biology. 2022; 11(10):1507. 

  1. Markhus, M.W., Kvestad, I., Midtbø, L.K. et al. Effects of cod intake in pregnancy on iodine nutrition and infant development: study protocol for Mommy’s Food - a randomized controlled trial. BMC Nutr 4, 7 (2018). 

  1. Boakye E, Kwapong YA, Obisesan O, et al. Nativity-Related Disparities in Preeclampsia and Cardiovascular Disease Risk Among a Racially Diverse Cohort of US Women. JAMA Netw Open. 2021;4(12):e2139564. doi:10.1001/jamanetworkopen.2021.39564 


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