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Iodine (Potassium Iodide / Kelp)
Essential trace mineral for thyroid hormone production — deficiency is common and affects metabolism, energy, and cognition.
What the evidence says
Studies are split: Iodine helped in 4 of 11 cases, with the rest inconclusive or showing no benefit.
Most evidence is from high-quality meta-analyses and randomised trials published 2009–2026 with a typical study size of 651 participants.
Based on 28 studies · 20 meta-analyses · 4 RCTs · 60,922 total participants
Confidence
HighWhat the studies found
By outcome
Iodine has an evidence score of 9/10 — very strong evidence based on 28 indexed studies, including 28 meta-analyses. Essential trace mineral for thyroid hormone production — deficiency is common and affects metabolism, energy, and cognition.
The commonly studied dose of Iodine is 150-300mcg for maintenance; higher only if deficient under supervision. Research points to an estimated optimal dose around 220mcg, with a minimum effective dose near 150mcg. Individual response varies — start low and adjust.
The best time to take Iodine is in the morning. Taking it with food is preferred. Iodine is an essential trace element required for thyroid hormone synthesis (T3 and T4).
Last reviewed May 2026 · evidence from 38 studies · how we score
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
Iodine is essential for synthesizing thyroid hormones T3 and T4, which regulate metabolism, energy, body temperature, and brain development. Deficiency remains common worldwide despite iodized salt, particularly in those avoiding salt or eating organic/unprocessed foods. Supplementation benefits those with true deficiency but excess can harm thyroid function.
Essential building block for T3 and T4
How Iodine works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
150-300mcg for maintenance; higher only if deficient under supervision
Take with food
| Form | Type |
|---|---|
| 💊Potassium iodide (most common and studied) | Recommended |
| 💊Kelp (natural but variable) | Alternative |
| 💊Nascent iodine | Alternative |
| 💊Lugol's solution | Alternative |
Kelp iodine content varies widely. Potassium iodide is more reliable for precise dosing.
Minimum: 8 weeks
Optimal: weeks
Cycling: Not required
Note: Can be taken any time. Consistent daily intake matters more than timing.
You can get iodine from these foods and drinks. Doses are typical per-serving estimates — actual content varies by brand, brew, cooking, etc.
400 mcg per tsp
1/4 tsp delivers ~100 mcg. 1 tsp ≈ 400 mcg (well above 150 mcg RDA).
7500 mcg per 5 gs
5 g dried (e.g., 1 sheet nori = ~3 g, 1 tsp kombu flakes). Kombu can exceed 2000 mcg per g — easy to overdose.
Based on meta-analyses showing urinary iodine concentration increases with supplementation. Effects only meaningful in iodine-deficient populations. Excessive intake (>300mcg) may increase thyroid cancer risk. Most studies used potassium iodide; kelp-derived forms have variable bioavailability.
Restored thyroid function if deficient
Better energy and metabolism
Higher needs (220-290mcg); essential for fetal brain development
Controversial — may worsen autoimmune activity; consult endocrinologist
May alter thyroid medication requirements
Additive hypothyroid effects
Potassium iodide adds potassium load — may affect electrolyte balance or enhance fluid loss — may affect electrolyte balance or enhance fluid loss
Tip: Don't exceed recommended dose; monitor thyroid
Tip: Take with food
Tip: Reduce dose
Iodine is generally safe at recommended doses, with a few precautions worth noting. The most commonly reported side effects are thyroid dysfunction, metallic taste, acne/skin breakout. Use caution if any of these apply to you: Hyperthyroidism; Hashimoto's (use with extreme caution); Dermatitis herpetiformis.
Selenium
Likely helpsRequired for selenoprotein production that regulates thyroid hormones, powers glutathione peroxidase, and strengthens immune defense.
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