Doctors and researchers find themselves 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 vital for many aspects of human development, especially in children. Specialists like Monica Serrano-Gonzalez, MD, pediatric endocrinologist and associate professor of pediatrics, are hoping that recent studies like one she supervised in the American Association of Clinical Endocrinology’s Clinical Case Reports can shed light on how to combat a growing challenge that transcends many demographics.
This interview has been edited for length and clarity.
Why do we need iodine?
Our bodies need iodine to make thyroid hormone, which helps regulate metabolism and is key to brain development. Without enough iodine, the gland has to figure out ways of compensating, which is why someone can have a goiter, when the thyroid becomes enlarged, and be otherwise OK. 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, in the worst case scenario you could go into a coma.
Why is there an increase in iodine deficiency?
There are very few food sources for iodine. The main ones are dairy products, seafood, 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. 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, which found that 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, but salt fortification made a big difference.
Part of the problem is that now there are a lot of trendy salts—Himalayan, sea, kosher, and others—so people have moved away from eating iodized salts. Organic dairy also has less iodine, and processed foods and bread usually lack it as well. You also have patients with restricted diets like veganism, dairy intolerance, food allergies, and autism spectrum disorder, which increase the risk. 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 US, so many salts don’t have iodine and the salts that do have varying concentrations. The public health messaging has been so strong against salt due to blood pressure issues, and people appear to be hyper aware of it. In the clinic, we have noticed there is confusion, where patients think that iodized salt specifically is bad for your health, as opposed to all types of salt.
Why did you start studying this?
I saw a 13-year-old patient in my clinic a few years back who had a rapidly enlarging goiter over 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 your immune system is misfiring and attacking your own body, in this case 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, and 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 sparked interest among myself and my colleagues, so we began paying attention to this, and eventually published a case series reporting our experience with six patients. All of them shared a restricted diet, due to reasons like developmental delays, autism, vegan diets, and dairy intolerance, which put them at risk. We are seeing this spanning all ages, from toddlers to adolescents, and in patients belonging to different socioeconomic groups.
How can physicians address this?
One of the things we are learning is the stigma associated with iodine deficiency. Diet is always a tricky subject, but I also think that there is a stigma, 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 trainees who work with us in the clinic, and we will give a hospital-wide Grand Rounds at Hasbro Children’s on the topic of micronutrient deficiencies, including iodine, later this year.
To avoid deficiency of iodine and other micronutrients, we encourage patients to have an increased dietary diversity. 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 for reasons like food allergies, autism, developmental delay, dietary preferences, or others, we recommend that they use iodized salt when cooking, in moderation and in the context of a healthy diet.