Iodine range
Iodine in Kelp and Seaweed: Why Amounts Vary Widely
Iodine in kelp varies enormously, from about 16 mcg per gram in nori to over 8,165 mcg per gram in processed kelp granules. Species, harvest and processing all change it. Labels can be wrong too. Prostadine lists four seaweeds and iodine alone, with no amounts, so its daily iodine total is unknown.
Written by the Prostadine label deskUpdated · 4 min read
How much iodine is in kelp and seaweed?
The iodine in kelp and seaweed ranges from tiny to far above the daily limit, depending on the type. One analysis of 12 dietary seaweeds found nori at 16 mcg per gram and a kelp granule product above 8,165 mcg per gram (Teas et al., Thyroid 2004).
The NIH puts commercial seaweed in whole or sheet form between 16 and 2,984 mcg per gram, and sets the adult limit at 1,100 mcg a day (NIH ODS, Iodine). A single gram of the highest kelp can pass that limit by itself.
| Item | Reported iodine |
|---|---|
| Nori | About 16 (Teas et al., Thyroid 2004) |
| Whole or sheet seaweeds (range) | 16 to 2,984 (NIH ODS, Iodine) |
| Processed kelp granules | Over 8,165 (Teas et al., Thyroid 2004) |
| Adult daily limit (all sources) | 1,100 mcg a day (NIH ODS, Iodine) |
Why does the iodine in kelp vary so much?
It varies because seaweed is a wild or farmed crop, not a fixed recipe. Species, growing conditions and processing all shift the number.
In two Namibian kelps, blades ranged from 514 mcg per gram when sun-bleached to 6,571 mcg per gram when fresh and young. Cooking also removes iodine, so food intake is hard to estimate (Teas et al., Thyroid 2004).
Supplements add another problem. A study of 96 seaweed products found supplements held between 5 and 5,600 mcg per daily dose, and in 54 products a single portion or dose passed the limit. Labels were often inadequate or wrong (Aakre et al., Food Nutr Res 2021).
Iodine
Seaweed supplements have measured up to 5,600 mcg in one daily dose.
Bars compare study doses or official limits with each other, not with Prostadine: its amounts are not printed, so its bar stays empty. No trial has tested Prostadine itself.
The bars show official limits and study amounts, with an empty bar for Prostadine because its iodine amount is not printed.
What can too much seaweed iodine do?
Too much iodine can disturb the thyroid. High intakes can cause goiter, raised TSH, underactive thyroid and also overactive thyroid (NIH ODS, Iodine).
One case report describes a 70-year-old woman who developed a racing heart, insomnia and weight loss after taking kelp tablets. Her thyroid returned to normal after she stopped. A case report shows harm can happen, not how often (Gherbon et al., Medicine 2019).
Ask before using seaweed products if you have a thyroid condition, take thyroid medicine or an antithyroid drug, or take an ACE inhibitor or potassium-sparing diuretic (NIH ODS, Iodine).
Brown seaweeds such as kelp and wakame also hold the most arsenic, mostly as arsenosugars (Yu et al., Food Chem Toxicol 2024).
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See packsWhat does this mean for Prostadine?
Prostadine names nori, wakame, kelp and bladderwrack, plus iodine on its own, and prints no amount for any of them (Prostadine sales page). Total iodine in 2 ml is therefore unknown.
The sales page calls kelp "Keeps the system toxin-free" and "Supports a strong urine flow". We found no human trial of kelp for either.
Ask for the panel
Request a Supplement Facts panel with iodine in mcg. See what is not printed.
Add up all sources
Count food seaweed, kelp tablets and multivitamins.
Check the pages
Read the iodine page and the seaweed extracts page.
Keep taking prescribed medicine.
Order Prostadine
Thinking of trying it? The bigger packs cost less per bottle.
Prices from the sales page, October 19, 2026 (Prostadine sales page). The 2-bottle pack is $79 a bottle plus $9.99 shipping. Every pack carries the 60-day money-back guarantee. Check your medicines first.
FAQ01
Quick answers on seaweed iodine
Does cooking seaweed lower its iodine?
Yes, some iodine is lost in cooking, which makes the amount in a meal hard to estimate (Teas et al., Thyroid 2004). That also means a cooked dish cannot be matched to a label for a dried product, so compare like with like.
Is nori lower in iodine than kelp?
In the data we read, yes. Nori measured about 16 mcg per gram, while processed kelp granules passed 8,165 mcg per gram (Teas et al., Thyroid 2004). Still, a product's own number matters more than the plant's name.
Can a seaweed supplement label be trusted for iodine?
Not always. In a study of 96 seaweed products, species and iodine declarations were inadequate or inaccurate for several (Aakre et al., Food Nutr Res 2021). Look for third-party testing, and ask the maker for a certificate of analysis.
Who wrote this02
Written and reviewed by
Pages built from the bottle front, the sales page and linked NIH, FDA, FTC and peer-reviewed sources.
Last updated . See our editorial standards and how we check reviews. This website is run by Goprostadine, a USA Authorized Prostadine Retailer, not by the manufacturer. We are paid when you buy through our order links.
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