Iodine
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
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.
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.
Iodine on Amazon
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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.
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.