Is Iodine Deficiency a Bigger Problem Than We Think?
Iodine is important for thyroid health, fetal growth, mental health, and more. However, iodine intake is decreasing, especially in certain populations. Read on to learn the impacts of low iodine intake, who is at risk, and how to treat iodine deficiency.
Iodine is required to synthesize the thyroid hormones T3 and T4. Because of iodized salt programs, the United States has been considered iodine-replete since around the 1920s. However, iodine intake has been decreasing since 1971, when the National Health and Nutrition Examination Surveys (NHANES) began monitoring iodine status. In 1971, iodine levels determined from urine tests were 320 mcg/L (1). By 2010, average iodine concentration dropped to 144 mcg/L. Below 100 ug/L is considered deficient for an adult, while anything below 150 mcg/L is below optimal for pregnant women.
Iodine deficiency affects more than 2.2 billion people worldwide. In the Western world, iodine deficiency affects multiple demographics more than many practitioners realize (2):
- In the NHANES studies, pregnant women and women of childbearing age had the lowest median iodine levels (3, 4, 5)
- In a study of Boston mothers, 47 percent of breast milk iodine samples were insufficient (6)
- In Europe, it’s estimated that up to 44 percent of the population may be iodine deficient (7)
- In school-aged children in New Zealand, a whopping 83 percent were iodine deficient (8)
Patients Are Not Consuming Enough Iodine-Rich Foods
Table salt is fortified with iodine, but this method of mass supplementing may no longer be sufficient. First, although the consumption of salty, processed food has skyrocketed over the past several decades, these products are generally not made with iodized salt. Second, sea salt, which is becoming more popular, doesn’t contain iodine either. Furthermore, due to fear of hypertension, many patients are instructed to severely restrict salt intake (which is somewhat misguided, anyway).
Most of the world’s iodine is found in the oceans. Therefore, the richest dietary sources are from the sea: sea vegetables like kombu, nori, and kelp and saltwater fish and fish heads. Regular consumption of these sources is rare in the United States.
Dairy products contain a little iodine, but most of it comes from iodophor, a cleanser used to sterilize milk tanks, and from cow feed, which is supplemented with iodine in the United States. Eggs are another minor source of iodine.
Are you getting enough iodine on your Paleo diet?
Who Is at Risk for Iodine Deficiency?
Considering the best dietary sources of iodine, specific demographics are susceptible to iodine deficiency.
Vegans and Vegetarians
Veganism is increasingly popular, comprising 0.5 to 6 percent of the U.S. population, according to various estimates. Estimates of vegetarians range from 2 to 10 percent of the population. Some of the most nutrient-dense foods are properly sourced animal products, and so it should come as no surprise that vegetarians and vegans are at risk for a number of nutrient deficiencies, including vitamin B12, calcium, zinc, vitamin A, vitamin D, and iodine.
Vegans are especially susceptible to iodine deficiency. In the literature, vegans repeatedly have low iodine intake and/or iodine deficiency (9, 10, 11, 12, 13). The only exceptions were vegans who consumed seaweed, a very rich source of iodine (12).
Vegans and vegetarians may also consume relatively high quantities of vegetables from the genus Brassica, including broccoli, kale, Swiss chard, and Brussels sprouts. These vegetables contain goitrogens, which in large doses inhibit iodine uptake by the thyroid. Therefore, even above-adequate iodine intake may not be enough to counter the goitrogen effects.
The ideal Paleo diet should include saltwater fish and sea vegetables, but if these aren’t consumed on a regular basis, Paleo dieters may be susceptible to iodine deficiency, especially if they aren’t consuming any dairy products. In one study that compared a Paleolithic diet to the Nordic nutrition recommendations for two years, the Paleo dieters had significantly lower iodine status (14). Patients on a Paleo diet should be sure they are consuming adequate iodine-rich foods.
During pregnancy, iodine requirements increase by 50 percent, due to an increased glomerular filtration rate and the needs of the fetus. If women aren’t consciously making an effort to consume iodine-rich foods, their diets may fall short. Between 1971 and 2008, the percentage of pregnant women with severely deficient urinary iodine levels (<50 mcg/L) increased from 4 to 15 percent (15).
A fetus’s thyroid isn’t developed until after the first trimester, and so he is completely dependent upon the mother’s properly working thyroid, including replete iodine. Iodine is especially important for fetal brain development and proper myelination of the central nervous system.
Those with High Exposure to and/or Suboptimal Detoxification of Environmental Toxins
Environmental toxins may contribute to iodine deficiency in Western populations. Perchlorates, thiocyanates, and nitrates all compete with iodine in the sodium-iodine symporter present in thyroid and lactating breast tissue (16). Therefore, people with high exposure to these toxins or people who have trouble properly detoxing these substances may have trouble incorporating iodine into the thyroid.
Perchlorate is used as an oxidizer for rocket fuels and a propellant in explosives. In the NHANES 2001–2002 study, perchlorates were present in all 2,820 urine samples (17). Several studies have found no association with perchlorate levels and thyroid function (18, 19), except when also in the context of iodine deficiency (20).
Thiocyanates are found in vegetables in the genus Brassica, as discussed above, but they are also present in cigarette smoke. Nitrates are found in drinking water, processed meats, and some leafy and root vegetables.
Risks of Iodine Deficiency
Iodine deficiency disrupts thyroid function and inhibits proper production of T3 and T4, which can lead to a variety of health problems.
Subclinical hypothyroidism (SCH) is generally diagnosed from high levels of thyroid-stimulating hormone (TSH) but normal T3 and T4 levels. Symptoms of this condition are varied and can include mental slowing, depression, dementia, weight gain, dry skin, hair loss, cold intolerance, hoarse voice, irregular menstruation, infertility, muscle stiffness, and pain. Untreated SCH can lead to clinical hypothyroidism and swelling of the thyroid (goiter).
SCH during pregnancy increases the risk of miscarriage, gestational diabetes, and preterm delivery (21, 22, 23). The prevalence of SCH during pregnancy may be as high as 15 percent (24), but proper diagnosis is challenging. Appropriate levels of TSH during different trimesters are not well established. Due to the suppressed immune system that accompanies pregnancy, thyroid antibodies, which may actually indicate an autoimmune thyroid disease versus iodine deficiency, may not be detectable.
Especially important for developing brains, iodine is critical for babies in utero and young children. Mild iodine deficiency during pregnancy is associated with decreased IQ and increased risk of attention deficit disorder in the children (25, 26). Severe iodine deficiency can result in cretinism, which is characterized by mental retardation, dwarfed state, bone dystrophy, and low basal metabolism. Iodine supplementation during pregnancy has been shown to reduce neonatal mortality and improve IQ scores (27, 28).
Iodine concentrations are higher in breast tissue even than in the thyroid, to provide plenty of iodine for the breastfeeding infant (29). There is some evidence in animals that iodine-deficient breast tissue is more susceptible to the effect of carcinogens and therefore increased risk of cancer (30). The Japanese, who probably have the highest consumption of iodine in the world, have less than one-third the incidence of breast cancer than do Americans (31). When these women emigrate to the United States and adopt the Standard American Diet, their breast cancer risk rises to that of other American women.
Testing for Low Iodine
Many conventional doctors measure iodine using a spot urine check. However, this won’t give an accurate picture of iodine levels. One study reported that 12 or more spot urine checks are needed to achieve precision within 20 percent (32).
I prefer to test for iodine levels using a combination of three tests:
- First, a 24-hour urine iodine test involves collecting and then testing entire urine output for 24 hours.
- Second, a hair iodine test is a good marker for long-term iodine status (33).
- Last, serum thyroglobulin (not the antibody), reversely correlates well with iodine levels.
Treatment for Low Iodine
Patients who are iodine-deficient need to increase both iodine and selenium intake, preferably from foods.
Selenium helps protect against iodine toxicity by ensuring that glutathione peroxidase activity in the thyroid is adequate to avoid cytotoxicity of hydrogen peroxide (34). Selenium is also required for the deiodinase enzymes that convert T4 to T3. Good dietary sources of selenium include Brazil nuts, crimini mushrooms, cod, shrimp, tuna, halibut, salmon, scallops, chicken, eggs, shiitake mushrooms, lamb, and turkey.
To increase iodine intake, kelp flakes can be used in place of salt, while other forms of seaweed can be used for flavoring foods.
Over-supplementing with iodine can contribute to Hashimoto’s disease or hyperthyroidism, especially when accompanied by selenium deficiency. Long-term supplementation with selenium is also not advisable, since it leads to fatigue, GI upsets, mild nerve damage, and more (35).
If supplementation is necessary, start with a small dose of iodine, one 325 mcg kelp tablet per day. Increase the dose by one tablet every three weeks up to 3 tablets a day, unless hyperthyroid-like or detox symptoms occur. Once the patient improves, the dose can slowly be scaled down again. Very short-term supplementation of selenium, 200 mcg per day for a couple months, can be safe but requires extra precaution.
Frequently Asked Questions:
Iodine deficiency affects more than 2.2 billion people worldwide. In the Western world, iodine deficiency affects multiple demographics more than many practitioners realize
Thanks for bringing this topic to the forefront and for presenting a comprehensive overview (what we have learned is the CK-style). I assess clients on an individual basis looking as dietary intake, biomarkers including a complete thyroid panel with RT3 and assess other nutrients related to thyroid function using Spectracell (that are easier to test than iodine). When I suspect a low iodine problem I encourage adding it into the diet using organic kelp flakes. When I suspect a more severe deficiency I refer my clients out to local Functional Medicine docs or sometimes have them run a 24 hour urine iodine test via a direct to consumer labs like Direct Labs. I would like to know other clinicians thoughts on testing for iodine. One other thought is that when I have clients with thyroid problems who spend a lot of time in chlorine swimming or water aerobics I automatically suspect iodine deficiency.
I supplement with two tablets of 12.5 mg of iodine and potassium iodide. I echoing have hypothyroidism. I found that my levels on the Armour has stayed really good since I’ve been taking the iodine with my Armour and I’ve never felt better
Supplement with kelp and selenium is the way to go…but, your recommendation to eat animal products cannot be justified…..anatomical structure of humans compared with carnivores distinctly show humans were meant to be herbivores…all of the longest living animals are herbivores.. and, as a super athlete myself at 84 yrs I can vouch that when you change to a plant-based diet, the impact on your performance will be tremendous and you will be at lower risk of developing heart disease, colorectal, ovarian and breast cancers, diabetes, obesity and hypertension…Plant foods are the fuel of winners ..and I would be happy to provide you with a list of some 25 scientific papers ..
OH GOOD GAWD! My father went to 90, good health almost to the end and he was definitely NOT a vegan or vegetarian.
As far as “scientific papers” most Paleo enthusiasts can throw PLENTY more than your 25 back at you showing how vegetarians have LOWER life expectancy!
“Scientific” papers mean diddly! Your 84 year old life span means diddly as well.
What makes the biggest difference is “whole, unadulterated, real” food, good control over stress, good relationships, regular paleo-esque daily movement, good sleep hygiene and a healthy zest for life.
I use iodine in my practice daily! I have been doing cervical iodine treatments for conditions that commonly affect women’s health and see some Amazing results. It softens breast tissue, dissolves breast cysts, helps with shrinking fibroids and treats ovarian cysts. My favorite result so far… Increased milk supply for some mom’s. Truly a miracle for so many of my patients.
Chlorine, fluoride and bromine block the absorption of iodine.
200 mcg of Selenium what I see in most multivitamins. Especially the higher quality ones. Do you consider this an unsafe amount for regular supplementation?
Thanks for all your work!
Is there a hair/urine/thyroglobulin combo test kit available? If not, where are you ordering these tests?
Thank you for this article. I generally recommend a moderate seaweed intake for my hashimotos patients and myself provided there is not evidence of hyperthyroid – now I am wondering if for some that may not be enough.
I have been wondering if the coca pulse can help a patient determine in real time whether an easily absorbed form of iodine like iodized salt or powdered kelp is appropriate in the moment since Hashis symptoms can be similar for a hyper or hypo state at times. I am always looking for ways to teach my Hashis patients how to recognize instability so they can make changes with foods, supps or synthetic thyroid before getting into see me if needed.
Anyone have experience with this?
I have autoimmune thyroiditis, since Feb 2017, I have been in remission (no antibodies), due to eating very little sugar(primarily fructose), no gluten and no dairy and soy products or processed foods. I read many controversial things about Iodine intake and I am a bit unsure if I have to consume iodine or not. I have been avoiding it for the last two years. Should I start supplementing and which iodine test is the most accurate? I am just asking because I am now pregnant. Looks like all has to come with moderation (not too much, not too little?)
Great iodine summary. I find conflicting evidence for iodine supplementation in Hashimoto’s patients with existing iodine deficiency. Is it safer to use food sources of iodine and supplement with selenium for short period of time (if selenium deficient)? Or is it best to optimise selenium first and then focus on iodine?
So, how do you recommend to increase the daily intake if I use sea salt?