Macrocystis Pyrifera
Giant kelp is a high-iodine seaweed; regular intake can deliver iodine well above the adult UL (1,100 µg/day) and may disrupt thyroid function. It can also accumulate arsenic and heavy metals; alginate derivatives from it are well-tolerated food additives.
What it is
Macrocystis pyrifera (giant kelp), a large brown seaweed harvested for alginate, food, and supplements.
Source of alginate (E400-E404), iodine, and minerals; whole seaweed in some foods.
Why it's flagged
- High iodine — risk of thyroid dysfunction
- Possible heavy metal/arsenic accumulation
What regulators actually say
"Tolerable Upper Intake Levels for iodine for adults is 1,100 mcg per day; intake from kelp products can substantially exceed this."
"Inorganic arsenic in algae and algae-based food products can contribute significantly to exposure."
Regulatory status
United States — FDA
GRAS as a natural flavoring/seaweed (21 CFR 184.1120 — algae). Alginates regulated separately.
European Union — EFSA
Edible seaweed under EU food law; EFSA has flagged iodine and inorganic arsenic in seaweed products.
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