Kelp | whatsinit

About

What it is and where it shows up.

Kelp is a group of large brown seaweeds of the order Laminariales, consumed as whole food and used as a food ingredient globally—especially in East Asian cuisines—for its high iodine, mineral, and dietary fibre content; its extracted polysaccharides (alginates, fucoidan, laminarin) are also used as thickeners and gelling agents. It is not a single chemical compound and carries no INS/E number as a whole food.

Safety summary

The regulatory and scientific consensus.

Kelp preparations are generally recognised as safe (GRAS) in the US and broadly approved as food worldwide; however, Laminaria/Saccharina species accumulate extraordinarily high iodine concentrations—a single portion of some kelp products can exceed the EFSA tolerable upper intake level of 600 µg iodine/day many-fold, with iodine-induced hypo- and hyperthyroidism both documented in kelp-consuming populations. Kelp also bioaccumulates heavy metals (arsenic, cadmium, lead, mercury) from seawater, and regular or high-dose consumption can elevate exposure to these contaminants to potentially harmful levels.

Regulatory landscape

What food-safety regulators have decided.

Jurisdiction	Status	Note
FSANZ (Food Standards Australia New Zealand) (Australia)	Approved	Kelp and seaweed are approved as food in Australia. FSANZ has established maximum levels for inorganic arsenic in seaweed; imported food compliance data (2006–2014) showed a 21.5% failure rate for inorganic arsenic in seaweed samples. Use of generic terms like 'kelp' on product labels has been flagged as problematic for arsenic risk communication. France, New Zealand, and Australia permit iodine content up to 1000–2000 mg/kg DW in seaweed products.source
EFSA (European Food Safety Authority) (European Union)	Approved	Kelp/seaweed is approved as a food. EFSA's Scientific Committee on Food (SCF, 2002) established a tolerable upper intake level (UL) for iodine of 600 µg/day for adults. The 0.6 mg/day figure reflects the iodine UL, not an ADI for kelp per se. EU Commission Recommendation 2018/464 requires monitoring of metals and iodine in seaweed. EFSA 2023 scientific report quantified heavy metal and iodine exposure from seaweed consumption across 19 European countries and recommended further work to consider setting maximum levels.source
MHLW (Ministry of Health, Labour and Welfare) (Japan)	Approved	Kelp (kombu, Laminaria spp.) is a staple food with a long history of safe use in Japan. Average dietary iodine intake from seaweed in Japan (1–3 mg/day) far exceeds EFSA and WHO upper tolerable limits, yet the Japanese population appears to have adapted to high iodine intake; no formal maximum level for iodine in kelp is established.source

Who should approach with care

Whose guidance would steer them away.

Thyroid Disease — Excess iodine from kelp can trigger or worsen both hypothyroidism and hyperthyroidism in individuals with pre-existing thyroid conditions (Hashimoto's disease, Graves' disease, nodular goiter, history of partial thyroidectomy), as documented by the ATA and multiple clinical case reports of iodine-induced thyrotoxicosis from kelp ingestion.

Pregnancy — High iodine intake from kelp supplements during pregnancy has been associated with an increased risk of maternal thyroid dysfunction and potential adverse effects on fetal thyroid development; the ATA advises against kelp supplements containing >500 µg iodine during pregnancy, and a review of iodine supplementation in pregnancy recommends that women planning to conceive, or who are pregnant, refrain from kelp supplements.

Lactation — High iodine from kelp is transferred into breast milk and can adversely affect the nursing infant's developing thyroid; the ATA advises against kelp supplements with >500 µg iodine daily during lactation, and Korean seaweed soup has been documented as a high-iodine health risk for lactating women and their infants.

Infants — Infants are highly susceptible to iodine excess—which can impair thyroid function and neurodevelopment—and are also at disproportionate risk from lead neurotoxicity due to lower body weight, per EFSA CONTAM Panel guidance on seaweed consumption in vulnerable subgroups.

Research citations

The sources behind this verdict.

1other. Kelp – LiverTox: Clinical and Research Information on Drug-Induced Liver Injury, 2024. ncbi.nlm.nih.gov
2EFSA. Dietary exposure to heavy metals and iodine intake via consumption of seaweeds and halophytes in the European population, 2023. efsa.europa.eu
3WHO. Report of the Expert Meeting on Food Safety for Seaweed – Current Status and Future Perspectives, 2022. openknowledge.fao.org
4PubMed. Commercially available kelp and seaweed products – valuable iodine source or risk of excess intake?, 2021. pmc.ncbi.nlm.nih.gov
5PubMed. Risks and benefits of consuming edible seaweeds, 2019. pmc.ncbi.nlm.nih.gov
6PubMed. Potential Risks of Excess Iodine Ingestion and Exposure: Statement by the American Thyroid Association Public Health Committee, 2015. pmc.ncbi.nlm.nih.gov

Independently researched6 citations