Korean sites say one sheet of seasoned gim passes the daily iodine recommendation. I checked the 348-sample lab study behind that

Hello I'm Korean, and I read Korean food and health sources for a small food blog I run (English isn't my first language, so sorry if something reads a bit off).

A Korean article from August 2025 says even one sheet of seasoned gim (roasted laver, about 2 g) carries 200 to 300 µg of iodine, which would pass the adult recommendation of 150 µg. It gives no source for the number, so I looked for measurements.

The best set I found is a 2025 paper from Korea's National Institute of Fisheries Science (Lee et al., Foods). They collected 348 seaweed samples from 12 coastal regions and measured iodine, in mg per kg of dry weight:

– Laver (gim): 100.18 average across 104 samples, with a range of 23.45 to 412.19

– Sea mustard (miyeok): 176.89

– Hijiki: 526.57

– Kelp (dasima): 2,432.11

One mg/kg is one µg per gram, so a gram of dried laver is about 100 µg at the average. 150 µg arrives at roughly 1.5 g. At the lowest sample it takes about 6.4 g and at the highest about 0.36 g. I did those divisions myself, the paper doesn't give them.

So the claim fits the average if the sheet is really 2 g of pure laver. A seasoned sheet also has oil and salt, and I didn't weigh one, so the weight on your own packet is the number to trust: grams on the pack x 100 is a rough estimate.

On what people eat: using Korea's 2023 national nutrition survey, the average person eats 1.02 g of dried laver a day, which is about 102 µg of iodine. People who reported eating laver that day averaged 2.94 g, about 295 µg. The paper's hazard index against Korea's 2,400 µg upper limit is 0.04 for the average person and 0.12 for laver eaters. Against the stricter 600 µg limit it takes from EFSA it is 0.17 and 0.49. Kelp eaters average about 1,633 µg a day.

One oddity: the paper's table gives kelp as about 24 times laver, while its text says "more than 45 times". Another Korean paper cites an earlier study with different ratios, so I wouldn't lean on any single multiple.

Sources:

– The 2025 paper (English): https://pmc.ncbi.nlm.nih.gov/articles/PMC12385538/

– The Korean article with the sheet claim: https://v.daum.net/v/tYUCMs0Cy0

My longer write-up with the tables and the grams-per-sheet math: https://koreantable1.blogspot.com/2026/10/korean-laver-gim-iodine-100-mgkg-vs.html

Do you check iodine when you eat a lot of seaweed? And how many grams are in a sheet of the gim you buy?