Should You Add Iodine to Your Diet?
As a 31-year-old female with normal thyroid function, you should ensure adequate dietary iodine intake of at least 150 mcg/day through iodized salt and iodine-rich foods (dairy, seafood), but you do not need iodine supplements if you are consuming a typical Western diet with iodized salt. 1
Why Adequate Iodine Matters for Euthyroid Patients
Iodine is essential for thyroid hormone production (thyroxine/T4 and triiodothyronine/T3), which regulate your metabolic rate and affect enzymes in fat and carbohydrate metabolism. 2
Even mild iodine deficiency in euthyroid individuals can lead to goiter, hypothyroidism, and autonomous thyroid nodules that become unresponsive to normal thyroid regulation. 2, 1
The thyroid gland has protective mechanisms that maintain normal function despite fluctuations in daily iodine intake, so you don't need to obsess over precise daily amounts. 3
How to Assess If You Need Supplementation
Most people in iodine-sufficient regions (like the United States) do not need supplements. 4 However, you should consider your iodine status if:
You avoid iodized salt or follow restrictive diets that eliminate dairy products and seafood. 2
You live in a region with known iodine deficiency (parts of Europe, including Switzerland, have documented mild deficiency). 2
You are planning pregnancy or currently pregnant/breastfeeding, as requirements increase to 220-290 mcg/day. 5
Proper Assessment Method
The gold standard is 24-hour urinary iodine excretion (normal: 100-300 mcg/24hr), combined with thyroid function tests (TSH, free T4, T3). 2, 1
Serum TSH alone is NOT a sensitive indicator of iodine status, as it usually remains normal despite frank iodine deficiency. 2, 1
Critical Warnings About Iodine Supplementation
The Danger Zone: Too Much Iodine
Excess iodine intake in euthyroid individuals causes elevated TSH, lower thyroid hormone levels, increased thyroid autoimmunity, hypothyroidism, and goiter. 2
Supplementation above 1,500 mcg/day causes measurable decreases in T4 and T3 with compensatory TSH increases, even though values remain within normal range. 6
Doses of 500 mcg/day or less do not affect thyroid function in healthy individuals. 6
Hidden Sources of Excess Iodine
Be vigilant about non-dietary iodine sources that can deliver massive loads: 1, 5
- Iodinated contrast agents used in CT scans and other radiologic studies 2
- Topical povidone-iodine disinfectants used for wound care 2, 1
- Amiodarone (anti-arrhythmic medication with very high iodine content) 2, 3
- Kelp and seaweed supplements, which can contain excessive amounts 4
Practical Recommendations
For Your Situation (Euthyroid, Age 31)
Use iodized salt in your daily cooking (provides approximately 60 mcg per gram of salt), which is the WHO-recommended strategy and rarely causes toxicity due to low iodine content. 2, 1
Include iodine-rich foods naturally: 2
- Dairy products
- Seafood
- Eggs
Do NOT take iodine supplements unless you have documented deficiency on 24-hour urine testing or are planning pregnancy. 1, 5
If You Were Planning Pregnancy
Pregnant and lactating women in iodine-deficient countries should take 150 mcg iodine supplements daily, which should be the mandatory dose in all prenatal vitamin/mineral preparations. 2
This is critical because even mild maternal iodine deficiency impairs fetal brain development, neurocognitive function, and reduces offspring IQ. 2
The Bottom Line Algorithm
If you use iodized salt and eat a varied diet including dairy/seafood → No supplementation needed 1
If you avoid these foods or live in known deficiency areas → Get 24-hour urinary iodine testing 2
If urinary iodine <100 mcg/24hr → Supplement with 150 mcg/day 2
If planning pregnancy → Start 150 mcg/day supplement regardless of current status 2, 5
Never exceed 300 mcg/day from supplements unless under medical supervision for documented severe deficiency 2
The key pitfall to avoid: supplementing "just in case" when you're already iodine-sufficient, which can paradoxically cause the very thyroid problems you're trying to prevent. 2, 1