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Iodine

Iodine (Potassium Iodide)
Also known as: Potassium iodide, Kelp iodine
Vitamin & Mineral

Content by: OpenSupplement Editorial Team  |  Medical review: pending  |  Last updated: April 13, 2026

Evidence ★★☆☆☆2/5
Best for
Cognition
Typical dose150 mcg/day (RDA)
SafetyWorth noting
Onset8+ weeks
Cost$5-8/mo
References2 studies cited

TL;DR

  • Trace mineral required for the production of thyroid hormones

  • Low evidence for cognitive and metabolic support (outside of deficiency)

  • Widespread use of iodized salt makes deficiency rare in the West

  • Excess can trigger thyroid issues (hyperthyroidism or Hashimoto's)

  • Very cheap: ~$5-8/month

  • Best for: Thyroid health in those with confirmed deficiency, pregnancy

What it is

Iodine is the 'fuel' for your thyroid gland. Your thyroid takes iodine and attaches it to an amino acid to make T4 and T3 hormones. These hormones control your metabolism, brain development, and body temperature.

While iodine deficiency is the leading cause of preventable intellectual disability worldwide, it is rare in developed nations thanks to iodized salt. However, those on 'gourmet' salt diets (Himalayan, sea salt) may be at risk of mild deficiency.

What the research says

Cognitive declineRelevance: Low
Evidence
2/5
Onset speed
1/5
Typical dose: 150 mcg/day (RDA)

Iodine is critical for developing brains but less proven for aging ones. Evidence. Severe deficiency leads to 'cretinism' and low IQ. In adults, mild deficiency can cause 'brain fog' and lethargy due to hypothyroidism. However, there is no evidence that extra iodine prevents Alzheimer's or cognitive decline in those with normal thyroid function. [1][2]

Metabolic syndromeRelevance: Low
Evidence
1.5/5
Onset speed
1/5
Typical dose: 150 mcg/day

Iodine only helps metabolism if your thyroid is struggling. Evidence. If you are hypothyroid due to low iodine, your metabolism will slow down, leading to weight gain and high lipids. Supplementing will 'fix' this. But if your thyroid is normal, more iodine will not boost your metabolism or help you lose weight.

DISCLAIMER: The information on this page is for educational purposes only and has not been evaluated by the Food and Drug Administration. This content is not intended to diagnose, treat, cure, or prevent any disease. Consult a qualified healthcare professional before using any dietary supplement, especially if you are pregnant, nursing, taking medication, or have a medical condition.

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Iodine on Amazon

$5-8/mo (estimated)
See on Amazon →

Safety

High risk of 'over-doing it.' Excess iodine can actually shut down the thyroid (the Wolff-Chaikoff effect) or trigger autoimmune thyroiditis. Do not supplement with high-dose iodine (like Lugol's solution) unless under strict medical supervision.

Interactions

  • Lithium: Significant interaction; can lead to severe hypothyroidism.
  • Anti-Thyroid Meds: Can have an additive effect.

Dosing

Standard Dose: 150 mcg daily (the RDA). Form: Potassium Iodide or Kelp-based supplements.

Cost

Dirt cheap. $5-8 per month.

The bottom line

Iodine is a foundational nutrient, but supplement with caution. Most people get plenty from their diet. If you suspect thyroid issues, get a blood test before reaching for the iodine.

References

  1. ReviewCognitive declinePubMed →
  2. NIH Fact SheetCognitive declineMetabolic syndromeSource →

Sources for this page include published meta-analyses, systematic reviews, and NIH dietary supplement fact sheets. All claims reflect the evidence as of early 2026.

This is not medical advice. Consult your healthcare provider before starting any supplement, especially if you take medications.