What's inside seaweed, and where does it go in your body?
A rich iodine source — sometimes too rich. Kelp can contain enough iodine to exceed safe limits.
Iodine range
Iodine varies enormously between seaweeds; kelp supplements especially can provide many times the upper limit.
Evidence & sources
Seaweed iodine content is highly variable, and some kelp products provide iodine far above the upper limit. Evidence: established. Known: Composition analyses. Unknown: — Source: NIH Office of Dietary Supplements, Iodine — Health Professional Fact Sheet (Current revision).