PROVIDENCE, R.I. [Brown University] — Doctors and researchers are puzzled by a recent rise in what might seem like an antiquated problem: iodine deficiency.

Iodine, a trace element that helps regulate metabolism and produce vital hormones, is essential for many aspects of human development, especially in children. Specialists like Dr. Monica Serrano-Gonzalez, a pediatric endocrinologist and associate professor of pediatrics, clinician educator, at Brown University’s Warren Alpert Medical School, are hoping that studies like one she recently led can shed light on how to combat a growing challenge that transcends many population groups.

In a Q&A, Serrano-Gonzalez shared how experiences with patients inspired her and other Brown-affiliated colleagues to study iodine deficiency, and how they’re educating the public on how to get enough.

Q: Why are physicians seeing an increase in patients with iodine deficiency?

There are very few food sources for iodine. The main ones are dairy products, seafood and eggs, as well as meat and poultry. In some countries, grain products like bread are made with iodized salt, but this is usually not the practice in the United States. Other foods like fruits and vegetables have very low levels as they depend on the soil iodine content. 

In the 1920s, American manufacturers began adding iodine to table salt widely available in stores. Part of the problem is that now there are a lot of trendy salts — Himalayan, sea, kosher and others — so many people have moved away from eating iodized salts. Organic dairy also has less iodine, as do processed foods and bread. Patients who have restricted diets, such as practicing vegans or people with dairy intolerance, food allergies or autism spectrum disorder, are also at higher risk for deficiency. Children and pregnant or breastfeeding women are more susceptible, as their iodine requirements are higher.

There is no public health mandate for iodization in the U.S., so many of the salts you buy in the grocery store don’t have iodine, and the salts that do have varying concentrations. The public health messaging has been so strong against salt due to its connection with blood pressure issues, and people appear to be hyper-aware of that. In the clinic, we have noticed that patients often think that iodized salt, specifically, is bad for health, as opposed to all types of salt. 

Q: Why do we need iodine?

Our bodies need iodine to make thyroid hormone, which helps regulate metabolism and is key to brain development. Without adequate iodine, the gland has to figure out ways of compensating, which is why someone can have a goiter — enlarged thyroid — and be otherwise okay. But if you reach a point of chronic deficiency where you can no longer compensate, the thyroid hormone levels go down, so the pituitary gland makes more of another hormone that stimulates the thyroid. The thyroid gland grows as it tries to keep up, but simply can’t. 

In children, low thyroid function can significantly affect linear growth and cognitive development, causing irreversible intellectual disability, and it affects metabolism overall at any age. There are thyroid hormone receptors all throughout the body, and if thyroid hormone levels are severely low for a long time, that could lead to the worst case scenario of a coma.

Before iodine fortification in the 1920s, there were “goiter belts” around the Great Lakes, the Appalachian and Northwestern regions. There are reports that analyzed military data from the first world war that found 30% of young people from iodine-deficient areas couldn’t be recruited into the military because they had large goiters, as it was so common back then. Salt fortification made a big difference.

Q: Why did you start studying this issue?

I saw a 13-year-old patient a few years ago who had a goiter that rapidly enlarged over the course of a few weeks. We often see patients with goiters in the clinic, but the vast majority of the time it’s from an autoimmune condition called Hashimoto’s disease, where the immune system is misfiring and attacking the thyroid gland. However, the patient’s blood tests for the disease were all negative, so we were puzzled. This boy had autism spectrum disorder and had a highly restricted diet, so we started thinking it could be iodine deficiency. He wasn’t eating eggs, dairy or seafood, and his family cooked with non-iodized salt. A urine test confirmed he was deficient, so we added an iodine supplement to his diet and the goiter decreased in size over the next few weeks. Eventually, his family managed to expand his diet so that he wouldn’t need the supplement anymore.

This incident sparked interest among me and my colleagues, so we began paying attention to iodine deficiency. We eventually published a case series reporting our experience with six patients, who we tracked from diagnosis to follow-up care. All of the patients shared a restricted diet, due to reasons like developmental delays, autism, vegan diets and dairy intolerance. We are seeing iodine deficiency spanning all ages, from toddlers to adolescents, and in patients belonging to different socioeconomic groups.

Q: How can physicians address the risk of iodine deficiency?

One of the things we are learning about is the stigma associated with iodine deficiency. Diet is always a tricky subject to discuss with patients, but I also think that there is a stigma in this case due to the association of iodine deficiency with poverty in underdeveloped countries. 

In our pediatric endocrine practice, we are educating our patients about the risks of an iodine-free diet. We’re also educating pediatricians as well as medical residents and fellows who work with us in the clinic, and we will give a hospital-wide grand rounds presentation at Hasbro Children’s on the topic of deficiencies of micronutrients such as iodine. 

To avoid deficiency of iodine and other micronutrients, we encourage patients to diversify their diets. If you have a mix of foods in your diet including seafood, eggs, chicken and dairy, you are likely okay in terms of iodine intake. But especially for patients who have a low dietary diversity because of food allergies, autism, developmental delay, dietary preferences or other reasons, we recommend that they use iodized salt when cooking — in moderation and in the context of a healthy diet.

This Q&A was originally published on the Warren Alpert Medical School website.