Iodine is a trace mineral essential for the synthesis of thyroid hormones, with an atomic weight of 126.9u and a Recommended Dietary Allowance of 150µg for adults. Most people get it from iodised salt, seafood, or a daily iodine supplement.
Why Iodine Matters for Your Body
The thyroid gland - thyroid gland is a butterfly‑shaped endocrine organ at the base of your neck that stores iodine and uses it to produce the hormones triiodothyronine (T3) and thyroxine (T4). These hormones regulate metabolism, heart rate, temperature, and brain development. Without enough iodine, the gland can’t make adequate T3/T4, leading to a cascade of health problems.
Thyroid hormone refers to the two active molecules T3 and T4 produced by the thyroid gland. T4 is a pro‑hormone, while T3 is the metabolically active form that cells actually use. The conversion of T4 to T3 depends on the trace element selenium, a co‑factor for the deiodinase enzymes that perform this switch. When iodine is scarce, the gland slows hormone production, and the pituitary releases more thyroid‑stimulating hormone (TSH), a signal that the thyroid is under‑active. Persistent high TSH is a hallmark of hypothyroidism, a condition marked by fatigue, weight gain, cold intolerance, and slowed cognition.
When the body lacks sufficient iodine, it can develop what the World Health Organization calls iodine deficiency disorders (IDD). The most visible sign is a goitre, an enlarged thyroid that swells in the front of the neck. Less obvious symptoms include dry skin, hair loss, menstrual irregularities, and in severe cases, cretinism in children - a permanent impairment of mental and physical growth. Populations living far from the sea, those on restrictive diets, and pregnant women are especially vulnerable. A 2023 meta‑analysis of 87 studies showed that 42% of women of child‑bearing age in inland regions had urinary iodine concentrations below the WHO sufficiency threshold. For most healthy adults, a balanced diet provides enough iodine, but the safety margin is narrow. The recommended dietary allowance (RDA) of 150µg can be met with a single iodised‑salt shaker or a 150‑µg capsule. However, dietary habits have shifted: many households now use non‑iodised sea salt, inadvertently cutting intake by up to 80%. Supplements come in several formats: For most adults, the safe upper intake level is 1100µg per day. Exceeding this can trigger hyperthyroidism or thyroiditis, especially in people with pre‑existing thyroid nodules. Therefore, start with the RDA and adjust only under medical supervision. While iodine is safe within recommended limits, certain conditions warrant caution: Pregnant women should never exceed 500µg daily without a doctor’s advice, as excess iodine can impair fetal thyroid function. Children under six need only 90µg; giving them adult doses can cause temporary hypothyroidism. Real‑world anecdote: Sarah, a 32‑year‑old vegan from Edinburgh, added a 150‑µg iodine capsule to her routine. Within three months, her energy levels improved, her TSH dropped from 4.2mIU/L to 2.9mIU/L, and she no longer experienced monthly mood swings. Her case underscores how a modest supplement can fine‑tune the thyroid axis. Understanding iodine opens doors to several adjacent health topics. You might want to read about: The Recommended Dietary Allowance for adults is 150µg per day. Most people meet this through iodised salt or seafood, but a 150‑µg supplement is a reliable way to ensure adequacy. A low‑to‑moderate dose (150‑300µg) is generally safe, but high doses may increase thyroid‑autoantibody levels. It’s best to work with an endocrinologist who can monitor TSH and antibody titres. Kelp is very rich in iodine, often delivering 1500µg per gram. Because the content can vary widely, use a standardized supplement to avoid accidental excess. Common signs include a swelling at the base of the neck (goitre), fatigue, weight gain, cold intolerance, hair loss, and in severe cases, developmental delays in children. Yes. Consuming more than 1100µg daily, especially in individuals with pre‑existing nodular thyroid disease, can trigger excess hormone production and symptoms like rapid heart rate, anxiety, and heat intolerance. Selenium is a co‑factor for the enzymes that convert T4 into the active T3. Adequate selenium (≈55µg/day) ensures that the iodine you consume leads to the right amount of active hormone. Not necessarily. Iodised salt provides a steady low‑level source, which can complement a supplement and prevent accidental excess. Just monitor total intake.Recognising Iodine Deficiency
Who Gains the Most from an Iodine Supplement?
Choosing the Right Form and Dosage
Source
Iodine per Serving
Bioavailability
Typical Daily Dose
Kelp (dry)
1500µg
High (≈90%)
250‑500µg
Iodised Salt (1g)
45µg
Very High
3g (≈1tsp)
Potassium Iodide Capsules
150µg
Excellent
150‑300µg
Safety, Interactions, and Common Pitfalls
Putting It All Together - A Practical Plan
Related Topics to Explore Next
Frequently Asked Questions
How much iodine should an adult take daily?
Can I take iodine if I have Hashimoto’s disease?
Is kelp a good iodine source?
What symptoms suggest iodine deficiency?
Can too much iodine cause hyperthyroidism?
How does selenium interact with iodine?
Should I stop using iodised salt if I take a supplement?
mona gabriel
September 24, 2025 AT 07:09I used to think iodine was just for thyroid people until I started feeling like a zombie every winter. One capsule a day and suddenly I’m not sleeping 10 hours and still exhausted. No magic pill but it’s the quietest win I’ve had in years.
Phillip Gerringer
September 24, 2025 AT 22:52Anyone taking iodine without checking their TPO antibodies is playing Russian roulette with their thyroid. You’re not just supplementing-you’re fueling an autoimmune fire. The data is clear, stop being naive.
jeff melvin
September 26, 2025 AT 10:29If you’re vegan and not supplementing iodine you’re basically doing your body a disservice. The modern diet is a nutrient desert and you think kale is enough? Wake up.
Matt Webster
September 27, 2025 AT 11:19I get why people are wary of supplements but iodine is one of those things where the gap between deficiency and danger is really narrow. Start low. Track it. Don’t assume. Don’t panic. Just be consistent.
Stephen Wark
September 28, 2025 AT 13:33So let me get this straight-now we’re all supposed to pop pills because we don’t eat seaweed like ancient coastal tribes? What’s next, mandatory cave-dwelling for optimal gut health?
Daniel McKnight
September 29, 2025 AT 12:48The selenium-iodine dance is underrated. I take both like peanut butter and jelly. One without the other feels like trying to drive with only one wheel. Also, if you’re using sea salt, you’re basically drinking seawater with no iodine. It’s not ‘natural’-it’s just lazy.
Jaylen Baker
September 30, 2025 AT 09:43Just started 150mcg daily. Two weeks in. My hands aren’t cold anymore. My brain doesn’t feel like it’s wrapped in cotton. I didn’t know how bad it was until it got better. Thank you for this post.
Fiona Hoxhaj
October 2, 2025 AT 01:40It is profoundly concerning that the modern populace has become so divorced from ancestral nutritional wisdom that a trace mineral-once abundantly available through marine foraging-is now deemed a ‘supplement.’ One must ask: What other biological imperatives have we mistaken for optional?
Merlin Maria
October 3, 2025 AT 12:08There is no such thing as ‘moderate’ iodine for Hashimoto’s. Any iodine intake beyond dietary sources is a pharmacological intervention. You are not ‘supporting’ your thyroid-you are provoking it. The literature is unequivocal.
Nagamani Thaviti
October 3, 2025 AT 16:20Kamal Virk
October 5, 2025 AT 16:13While iodine deficiency is a documented public health issue in certain regions, the blanket recommendation for supplementation ignores the heterogeneity of individual physiology. A one-size-fits-all approach is not evidence-based medicine-it is dietary dogma.
Elizabeth Grant
October 6, 2025 AT 07:12For anyone scared to start because of Hashimoto’s-talk to your doc, get tested, and try 75mcg first. I did. No flare. Just more energy. You don’t have to go all-in to see a difference.
angie leblanc
October 6, 2025 AT 10:27Wait… so iodine supplements are just a government trick to make us dependent on Big Pharma while they secretly control our thyroid function? I read on a forum that the FDA banned kelp in 1998 because it was too effective… and they don’t want us to heal naturally.
LaMaya Edmonds
October 7, 2025 AT 11:39Let’s be real-this isn’t about iodine. It’s about how we’ve outsourced our biology to processed food and then pay $200 a month for supplements to fix what we broke. Iodine’s just the latest Band-Aid on a bullet wound.