Laver

BotanicalSeaweedBest with a meal

What is it

Laver is a group of edible red seaweeds (Porphyra and Pyropia species), best known as the source of nori used in Asian cuisine. It is consumed as food and used in supplements as a source of iodine, B12 (in some forms), and minerals.

Evidence for 1 use

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Iodine source

Good Evidence

Documented dietary source of iodine, though content is variable. Excess intake can disrupt thyroid function.

How it works

Laver provides iodine, protein, vitamin C, magnesium, iron, and (uniquely among plant foods) potentially bioavailable vitamin B12 in some forms. It also contains porphyran, a sulfated polysaccharide with antioxidant and immune-modulating activity in laboratory studies. Iodine and mineral content vary by species and preparation. The vitamin B12 content is controversial; some species and preparations contain corrinoid analogs that may not be active in human metabolism.

Dosage

Typically consumed as a food. Supplement use varies; typical sheet of nori (3 g) provides 30-50 mcg of iodine.

When and how to take it

WHEN: Anytime as food. HOW: Eat as a snack or with meals; supplements with water and food.

2 commercial forms

Compare the main delivery options and what they’re best suited for.

Dried nori sheets

Toasted, sliced seaweed used in Asian cuisine.

Well-tolerated culinary form.

Powdered supplement

Concentrated form used in capsules.

Variable composition.

Safety

Generally safe in moderate amounts. Excessive intake can deliver too much iodine, affecting thyroid function. Heavy metal contamination can occur in poorly sourced products.

Who should be cautious

Caution with thyroid disorders. Verify iodine content if you have hyperthyroidism, Hashimoto's, or are pregnant. Choose tested products to minimize heavy metal exposure.

Interactions

Iodine content interacts with thyroid medications (levothyroxine, methimazole).

Food sources

Nori (dried laver)

Amount
1 sheet (3 g)
%DV
—

Frequently asked questions

Can vegans get B12 from laver?⌄

Some research suggests certain laver species contain bioactive B12, but content varies and reliability is uncertain. Vegans should not rely on laver alone for B12; supplementation is more dependable.

References

Laver on Wikidata — Wikidata link

Laver on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on Laver (PubMed search) — PubMed link

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.