Ascophyllum Nodosum Powder
Ascophyllum nodosum is very high in iodine; intake can substantially exceed the adult tolerable upper intake level (1,100 µg/day) from small servings, potentially affecting thyroid function. It can also contain inorganic arsenic, prompting EFSA to caution about brown seaweed consumption.
What it is
Ascophyllum nodosum (knotted wrack) powder is a dried brown seaweed used in foods, supplements, and cosmetics; high in iodine and alginates.
Mineral source (iodine), thickener (alginate source), and nutritional supplement ingredient.
Why it's flagged
- very high iodine content (thyroid risk)
- potential inorganic arsenic accumulation
What regulators actually say
"The Tolerable Upper Intake Level (UL) for iodine for adults is 1,100 mcg/day; very high intakes can cause thyroid dysfunction."
"EFSA evaluated dietary exposure to inorganic arsenic and identified seaweed and seaweed-based products as significant contributors."
Regulatory status
United States — FDA
Permitted as a food/supplement ingredient; iodine content variability is a labeling concern.
European Union — EFSA
EFSA has flagged iodine and inorganic arsenic concerns for hijiki and other brown seaweeds.
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