Kelp (iodine-rich)

Tier 3 — weak evidence · Thyroid · Mineral · Contamination risk

Dried seaweed sold as a natural iodine source. Iodine content varies enormously between batches — some products contain dangerously high levels that cause thyroid dysfunction. Heavy metal contamination (arsenic, lead, cadmium) is a documented concern. People with thyroid conditions can experience serious flare-ups. Controlled-dose iodine supplements are safer.

Dose: 150–300 mcg iodine equivalent/day; variable iodine content makes dosing unreliable; contamination risk