Saccharina Japonica
Kombu is a nutrient-dense traditional food but is one of the most concentrated dietary sources of iodine, with a single gram potentially providing many times the daily Tolerable Upper Intake Level. Excess iodine intake from kelp can trigger thyroid dysfunction in susceptible individuals; arsenic content is also a concern in some kelp products.
What it is
An edible brown kelp (Saccharina japonica), known in Japan as kombu, used in stocks and as a food ingredient and source of iodine.
Umami-rich broth ingredient; iodine source; thickener via alginate content.
Why it's flagged
- very high iodine content — risk of exceeding Tolerable Upper Intake (1100 mcg/day adults)
- potential inorganic arsenic accumulation
What regulators actually say
"Seaweed (such as kelp, nori, kombu, and wakame) is one of the best food sources of iodine, but it is highly variable in its content."
Regulatory status
United States — FDA
GRAS use as food (seaweed); iodine content not specifically capped in food
European Union — EFSA
EFSA has set a Tolerable Upper Intake of 600 mcg/day for iodine in adults
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