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Types of Iodine (Thyroid): Forms & Bioavailability

Evidence:Strong
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This content is for informational purposes only and does not constitute medical advice. Statements about dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease. Individual results may vary — consult your healthcare provider before starting any supplement. Full disclaimer

Forms Comparison

FormBioavailabilityBest ForElemental Content
Potassium Iodide (KI)HighGeneral supplementation — most studied and widely available form76% iodine by weight
Kelp/Seaweed-derived IodineHighWhole-food source — variable iodine content, harder to dose precisely
Nascent IodineModerate-HighAtomic form in liquid — marketed as more bioavailable but lacking comparative studies

Potassium Iodide (KI)

Bioavailability: High. Best for: General supplementation — most studied and widely available form. Elemental content: 76% iodine by weight.

Kelp/Seaweed-derived Iodine

Bioavailability: High. Best for: Whole-food source — variable iodine content, harder to dose precisely.

Nascent Iodine

Bioavailability: Moderate-High. Best for: Atomic form in liquid — marketed as more bioavailable but lacking comparative studies.

References

  1. Zimmermann MB (2009). Iodine deficiency. Endocrine Reviews. DOI PubMed
  2. ReviewZimmermann MB, Jooste PL, Pandav CS (2008). Iodine-deficiency disorders. The Lancet. DOI PubMed
  3. ReviewSpallek L, Krille L, Reiners C, Schneider R, et al. (2012). Adverse effects of iodine thyroid blocking: a systematic review.. Radiation protection dosimetry. DOI PubMed
  4. RCTReinhardt W, Kohl S, Hollmann D, Klapp G, et al. (1998). Efficacy and safety of iodine in the postpartum period in an area of mild iodine deficiency.. European journal of medical research. PubMed