Understanding Why is my body not absorbing iodine?: Common Causes and Solutions

October 16, 2025 •

5 min read

According to the World Health Organization, insufficient iodine intake affects an estimated 1.9 billion people worldwide. For some, the issue isn't just low intake but poor absorption, leaving them wondering, "Why is my body not absorbing iodine?".

Quick Summary

Several factors can impair the body's ability to absorb iodine, including dietary goitrogens, poor gut health, co-factor deficiencies, and certain autoimmune conditions and medications. Identifying and addressing the underlying cause is key to restoring proper thyroid function.

Key Points

Identify the Root Cause: Poor iodine absorption can stem from dietary, environmental, or medical issues; a precise diagnosis is critical before intervention.
Manage Dietary Goitrogens: While healthy, certain foods like cruciferous vegetables and soy can interfere with iodine uptake, particularly with low iodine intake, though cooking can mitigate this.
Prioritize Gut Health: Digestive disorders, inflammation, and nutrient deficiencies can disrupt the absorption of iodine in the intestines, requiring targeted treatment.
Address Autoimmune Conditions: In Hashimoto's thyroiditis, the thyroid's ability to utilize iodine is impaired, and excessive intake can be harmful.
Assess Medications and Toxins: Certain medications and environmental chemicals can block the transport of iodine into the thyroid gland.
Balance Co-factors: Other minerals like selenium and iron are necessary for proper iodine metabolism; a deficiency can worsen absorption issues.
Seek Professional Guidance: Self-treating can be dangerous; always work with a healthcare provider to manage iodine intake and absorption.

The Intricate Process of Iodine Absorption

Iodine is an essential trace mineral that is crucial for the production of thyroid hormones, which regulate metabolism, growth, and development. The journey of iodine from your plate to your thyroid gland is relatively straightforward, yet vulnerable to disruption. Once consumed, dietary iodine is converted into iodide in the gastrointestinal tract and is almost entirely absorbed in the stomach and duodenum. From there, it enters the bloodstream. The thyroid gland possesses a highly efficient sodium-iodide symporter (NIS) system to actively trap and concentrate iodide from the blood. However, when this process is compromised at any stage, malabsorption can occur, leading to iodine deficiency disorders.

Goitrogens and Other Dietary Factors

While a balanced diet is the primary source of iodine, certain foods contain compounds known as goitrogens, which can interfere with the thyroid's ability to uptake and use iodine, especially in individuals with a marginal iodine status.

Cruciferous Vegetables: Cabbage, broccoli, cauliflower, and kale contain glucosinolates that, when metabolized, can produce compounds that compete with iodine uptake. Cooking these vegetables can help to reduce their goitrogenic effect.
Soy Products: Soy contains goitrogenic flavonoids that may interfere with iodine metabolism. Studies on infant formula containing soy flour have shown that it can inhibit iodine absorption.
Other Goitrogenic Foods: Cassava, millet, and certain varieties of sweet potatoes also contain goitrogenic substances.
Excessive Salt Restriction: For those who rely on iodized salt, a diet low in salt can inadvertently lead to insufficient iodine intake, particularly in pregnant women.

Gut Health and Digestive Disorders

Proper digestion and a healthy gut lining are fundamental for absorbing nutrients, including iodine. Various digestive issues can compromise this process:

Protein-Calorie Malnutrition (PCM): Severe protein and calorie deficiencies, particularly in children, can lead to intestinal malabsorption due to morphological changes in the intestinal wall, affecting iodine uptake.
Environmental Enteric Dysfunction (EED): Common in low-income settings, EED is characterized by chronic intestinal inflammation and increased gut permeability. Research suggests that both inflammation and a compromised gut barrier can negatively influence iodine status.
Inflammatory Bowel Diseases (IBD) and Celiac Disease: These chronic conditions cause intestinal inflammation and damage, which can disrupt the normal absorption of many nutrients, including iodine.

Autoimmune Thyroid Conditions

For some individuals, the issue of poor iodine utilization is rooted in an autoimmune response. In conditions like Hashimoto's thyroiditis, the immune system mistakenly attacks the thyroid gland.

Disrupted Uptake Mechanism: In autoimmune thyroiditis, the gland loses its normal ability to trap and store iodine efficiently. It becomes inefficient at producing thyroid hormone and its sensitivity to TSH stimulation is altered.
Iodine Sensitivity: While iodine is necessary, those with autoimmune thyroid conditions may be sensitive to excess intake. High levels of iodine from supplements or certain foods (like kelp) can sometimes cause or worsen hypothyroidism in these individuals.

The Role of Micronutrient Co-factors

Iodine doesn't work in isolation. The thyroid's complex process of hormone synthesis requires several other nutrients. A deficiency in these co-factors can indirectly impede the effective utilization of iodine.

Selenium: This mineral is vital for the enzymes that help convert thyroid hormones and protect the thyroid from oxidative damage. A selenium deficiency can exacerbate the effects of iodine deficiency.
Iron: Adequate iron levels are necessary for proper thyroid hormone production. Iron deficiency can impair the efficacy of iodine supplementation.
Vitamin A: Deficiency in vitamin A can also act as a goitrogen and interfere with thyroid function.

Medications and Environmental Toxins

External factors can also block iodine uptake, even when diet and internal health appear sufficient.

Medications: Certain drugs are known to interfere with iodine uptake. These include lithium (used for bipolar disorder), amiodarone (for heart arrhythmias), and antithyroid medications (methimazole, propylthiouracil). Iodine-containing cough medicines and contrast materials for imaging studies can also affect uptake.
Environmental Chemicals: Exposure to perchlorates (found in drinking water and some industrial products) and thiocyanates (from cigarette smoke) can competitively inhibit the sodium-iodide symporter (NIS), blocking iodide uptake by the thyroid.

Comparison of Key Factors Inhibiting Iodine Absorption


Factor	Mechanism of Action	What you can do
Goitrogenic Foods	Contains compounds that block thyroidal uptake of iodine.	Cook vegetables thoroughly; ensure sufficient overall iodine intake.
Gut Health Issues	Intestinal inflammation and damage impede absorption in the small intestine.	Diagnose and treat underlying digestive disorders with a healthcare provider.
Autoimmune Thyroiditis	The immune system's attack on the thyroid impairs its ability to use iodine.	Work with an endocrinologist to manage the condition and balance iodine intake.
Nutrient Deficiencies	Lack of co-factors like selenium and iron hinders effective iodine utilization.	Consume a balanced diet rich in these nutrients or consider targeted supplementation under medical guidance.
Medications/Chemicals	Certain drugs and environmental toxins block the NIS, preventing iodine uptake.	Consult a doctor about potential drug interactions; use water filtration if contamination is suspected.

Addressing Poor Iodine Absorption

To effectively address poor iodine absorption, a comprehensive approach is necessary, starting with identifying the root cause. This often requires consulting a healthcare provider, such as an endocrinologist or a functional medicine practitioner, to conduct tests like urinary iodine concentration to assess your status.

For dietary-related issues, adjusting your diet is the first step. While you should not avoid healthy goitrogenic foods entirely, especially if you have adequate iodine intake, cooking them can reduce their effect. Ensuring you use iodized salt or consume other iodine-rich foods like seafood and dairy can help. For those with gut health issues, treating the underlying condition is crucial to restoring nutrient absorption. This may involve working with a gastroenterologist or a registered dietitian. Addressing co-factor deficiencies, such as selenium or iron, can be done through diet or supplements, but should be managed under medical supervision. If medication is the issue, your doctor may be able to adjust the dose or prescribe an alternative. Lastly, if environmental toxins are a concern, filtering your water can help eliminate perchlorates.

Conclusion

Iodine malabsorption is a complex issue with a range of potential causes, from simple dietary habits to underlying medical conditions. Merely increasing iodine intake may not be the solution if your body is unable to process it effectively. By understanding the intricate mechanisms of iodine metabolism and identifying the specific factors hindering your absorption—whether it’s goitrogens, gut inflammation, an autoimmune response, or a medication—you can take targeted steps to address the problem. Working with a qualified healthcare provider is the most effective way to ensure your body gets the iodine it needs for optimal thyroid and overall health. For further information on iodine, you can refer to the National Institutes of Health.

Frequently Asked Questions

Yes, foods containing goitrogens, such as cruciferous vegetables (broccoli, cabbage, cauliflower) and soy products, can interfere with iodine uptake, especially if your intake is already marginal.

Absolutely. Conditions like inflammatory bowel disease, celiac disease, and chronic inflammation can damage the intestinal lining, impairing the absorption of nutrients like iodine.

In Hashimoto's, the immune system attacks the thyroid, disrupting its normal function and its ability to efficiently trap and utilize iodine, even when adequate amounts are present in the diet.

Yes. Certain medications, including lithium, amiodarone, and some antithyroid drugs, can interfere with iodine uptake and metabolism.

Deficiencies in key co-factors like selenium, iron, and vitamin A can negatively impact thyroid hormone production and, consequently, the body's use of iodine.

Yes. Exposure to environmental chemicals such as perchlorates (in water) and thiocyanates (in tobacco smoke) can inhibit the body's ability to take up iodide.

You should not take iodine supplements without consulting a healthcare provider first. Especially with conditions like Hashimoto's, excessive iodine can be harmful, and a doctor can help determine the correct course of action.

Diagnosis typically involves a healthcare provider assessing your symptoms, dietary habits, and medical history. Urinary iodine concentration tests can measure your iodine status, but identifying the specific absorption issue often requires further investigation.