Kombu
Kombu is a traditional food and a very concentrated source of iodine. Single servings can deliver iodine far above the IOM RDA (150 μg/day for adults) and even above the Tolerable Upper Intake Level of 1,100 μg/day; chronic high intake can cause thyroid dysfunction.
What it is
Kombu — edible kelp, primarily Saccharina japonica (formerly Laminaria japonica) — a brown seaweed widely used in Japanese, Korean, and Chinese cooking.
Umami-providing dashi base ingredient and side dish; major dietary source of iodine.
Why it's flagged
- very high iodine — risk of thyroid dysfunction at frequent intake
- potential heavy-metal accumulation (arsenic, cadmium)
What regulators actually say
"The Tolerable Upper Intake Level for iodine for adults is 1,100 mcg per day...Some seaweeds (such as kelp) contain very high amounts of iodine and can cause excessive iodine intake."
"Inorganic arsenic levels in seaweed (especially Hijiki and other brown algae) can be substantially elevated; the Panel considered seaweed as a contributor to inorganic arsenic dietary exposure."
Regulatory status
United States — FDA
Permitted seaweed food ingredient; iodine intake covered under FDA dietary guidance.
European Union — EFSA
Permitted food; EFSA has issued opinions on iodine intake from seaweed and on inorganic arsenic in food.
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