Ao-nori (Green Laver): Nutrients, What Research Shows and Safety
Ao-nori (green laver) as a food: Japanese dried flake nutrient values, iodine per gram, why it is not nori for B12, salt, naming mix-ups, and who should ask a clinician first.
Content last updated . This page has not been medically reviewed.
Ao-nori ("blue-green nori," also called green laver) is a green seaweed sold as dried flakes or powder. In Japan it is sprinkled on okonomiyaki, yakisoba, tempura and similar dishes. The Japanese food table describes ao-nori as a group of green algae in the Ulvaceae family, and says the product is mostly one species called sujiaonori with some usuba-aonori mixed in. [2][3] This page keeps the whole food apart from extracts and from hype.
Read this first
- Iodine is the main safety point. The Japanese food composition table lists 2,700 micrograms (mcg) of iodine per 100 g of dried ao-nori, about 27 mcg per gram. [2] About 41 g would reach 1,100 mcg, the adult upper limit quoted by the American Thyroid Association (ATA). [6] A sprinkle is far less. These are arithmetic from one table, not advice.
- People with thyroid disease, and pregnant or breastfeeding women, should ask a clinician before eating seaweed often. In 49 regular Norwegian seaweed eaters (species not named), thyroid-stimulating hormone (TSH) fell after six weeks without seaweed. [5]
- Ao-nori is not nori. Nori is purple laver, a red alga. The B12 research we read is about purple laver only. [8] Do not count on ao-nori for vitamin B12.
- Labels can mislead. The Japanese table notes that "aosa" (sea lettuce) is sometimes sold as ao-nori, and in some regions "hitoegusa" is called ao-nori. [3]
- Evidence in one line: ao-nori is a flavoring with measured nutrients. Proper evidence not found in the sources we read for disease treatment or prevention.
What is in it (USDA values)
No USDA entry for this food: USDA FoodData Central (SR Legacy) has no ao-nori item. The values below are from the Japanese Standard Tables of Food Composition (8th revised, 2023 supplement), item 09002 "aonori, sun-dried." [2] They are for the dried product (6.5 g water per 100 g), not rehydrated and not fresh. [2] The table gives no portion size, so the "per 1 g" column is our simple division by 100, to picture a pinch of flakes. Percentages use FDA 2016 Daily Values, calculated by us.
| Nutrient | Per 100 g dried | Per 1 g (our arithmetic) | % Daily Value in 1 g |
|---|---|---|---|
| Energy | 249 kcal | 2.5 kcal | not set |
| Protein | 29.4 g | 0.29 g | 1% |
| Dietary fiber (total) | 35.2 g | 0.35 g | 1% |
| Iodine | 2,700 mcg | 27 mcg | 18% |
| Iron | 77.0 mg | 0.77 mg | 4% |
| Manganese | 13.0 mg | 0.13 mg | 6% |
| Magnesium | 1,400 mg | 14 mg | 3% |
| Calcium | 750 mg | 7.5 mg | under 1% |
| Potassium | 2,500 mg | 25 mg | under 1% |
| Sodium | 3,200 mg | 32 mg | 1% |
| Vitamin A (retinol activity equivalents) | 1,700 mcg | 17 mcg | 2% |
| Vitamin K | 3 mcg | 0.03 mcg | under 1% |
The table also lists vitamin B12 at 41.6 mcg per 100 g, vitamin C at 62 mg and riboflavin at 1.66 mg. [2] We do not treat the B12 number as a B12 claim (see the research table). Values vary with species, harvest place and processing, and the table says its figures come from commercial samples. [3]
Plant compounds: the table gives beta-carotene equivalents of 21,000 mcg per 100 g. [2] We did not read a study of other plant compounds in ao-nori itself.
What research says
| Health goal | What the sources found | Strength of evidence | What was studied |
|---|---|---|---|
| Iodine intake and thyroid tests | In 49 habitual seaweed eaters (species not named), median iodine intake was 658 mcg a day before and 189 mcg after six weeks without seaweed. TSH fell significantly after stopping. [5] | Mixed (observational pre-post; not specific to ao-nori) | Regular seaweed eaters in Norway |
| Vitamin B12 | A review concluded that dried purple laver (nori) is the most suitable plant B12 source for vegetarians. It did not discuss green laver. [8] | Insufficient evidence for ao-nori | Nori only |
| Iron, fiber and protein | The table lists high amounts per 100 g (77.0 mg iron, 35.2 g fiber, 29.4 g protein). [2] A pinch supplies little; we found no study of ao-nori and iron status. | Insufficient evidence | Food composition table only |
| Iodine compared with other seaweeds | The Japanese health ministry page lists dried cut wakame at 10,000 mcg and shredded kelp at 230,000 mcg per 100 g. [9] A Korean survey of five edible seaweeds found sea tangle (a kelp) highest, at 2,432 mg per kg dry weight. [4] | Composition data (not a health outcome) | Food composition table |
| Weight loss, detox, cancer, blood sugar | Proper evidence not found in the sources we read | No good evidence of benefit found | Not applicable |
We found no human trial of ao-nori. Studies of extracts or other Ulva seaweeds are not the same food and are not used here.
How much is a normal serving
No official serving exists in the sources we read. USDA has no entry, and the Japanese table gives per 100 g values only. [2] For scale, 1 g of dried ao-nori is about 27 mcg of iodine and 2.5 kcal by simple division. [2] The ATA says intake above 1,100 mcg of iodine a day is not recommended, [6] and NHS says adults need 140 mcg a day. [7] This is information, not a prescription. For furikake mixes, see furikake.
Safety, allergy and medicines
- Iodine and thyroid: NHS says taking high doses of iodine for long periods could change how the thyroid works. [7] The ATA advises against iodine and kelp supplements above 500 mcg a day and says intake above 1,100 mcg a day is not recommended. [6] People with thyroid disease or on thyroid medicine should ask their clinician or pharmacist. We did not read a source on medicine interactions for ao-nori.
- Pregnancy and breastfeeding: the ATA encourages 220-250 mcg a day in pregnancy. [6] We found no source giving a safe amount of ao-nori. See seaweed in pregnancy.
- Salt: dried ao-nori lists 3,200 mg sodium, or 8.1 g salt equivalent, per 100 g. [2] That is about 0.08 g of salt per gram of flakes. The finished dish, sauces and seasoned mixes were not measured in sources we read.
- Vitamin K and warfarin: the table lists just 3 mcg vitamin K per 100 g. [2] We did not read a source on warfarin and ao-nori; ask your clinician if you take warfarin.
- Metals and pollutants: we did not find a measured arsenic, cadmium or lead value for ao-nori in sources we read. See the metals guide.
- Allergy and mixes: seaweed is not fish or shellfish. We did not read a source on ao-nori allergy. Seasoned mixes and okonomiyaki or yakisoba sauces can contain wheat, soy, fish or sesame, so read labels. For trouble breathing or swelling of the face or throat, call 911 (or your local emergency number). See food allergy basics.
Choosing, storing and food safety
- We did not read a source on ao-nori storage. For general advice see how to buy, prepare and store seaweed.
- Check what the jar really contains: aosa and hitoegusa are sometimes sold as ao-nori. [3] The iodine values differ (aosa 2,200 and ao-nori 2,700 mcg per 100 g dried). [1][2]
- The Japanese table says its ao-nori values rest on commercial samples. [3]
Related pages
Health connections for Ao-nori (Green Laver)
What research links to eating or drinking this food, and how strong the evidence is. Many studies are observational or use juice, powder, oil or extracts rather than the food as eaten; each card says which.
Ao-nori and vitamin B12 claims
Not enough evidenceThe Japanese table lists 41.6 mcg B12 per 100 g, but the B12 review we read found purple laver (nori), not green laver, useful for vegetarians.
Supplements: No evidence that ao-nori corrects B12 status.
Minerals and vitamins listed for dried ao-nori
Established roleThe Japanese table lists iron (77.0 mg), magnesium (1,400 mg), manganese (13.0 mg) and riboflavin per 100 g dried; a pinch supplies little.
Supplements: Composition only; no health benefit is claimed.
Fiber and protein in dried ao-nori
Established roleThe Japanese table lists 35.2 g fiber and 29.4 g protein per 100 g dried. Sprinkle amounts are small.
Supplements: No health outcome studied.
Aonori, aosa and hitoegusa: what the label may mean
Not enough evidenceThe Japanese table notes aosa (sea lettuce) is sometimes sold as ao-nori and hitoegusa is called ao-nori in some regions; iodine differs (2,200 vs 2,700 mcg per 100 g dried).
Supplements: Check the label and ask the seller.
Connected topics
Open a group to see how each topic connects and how strong the evidence is.
Body systems (1)
- Endocrine SystemDocumented risk
Iodine from seaweed can affect thyroid hormone balance when intake is high.
Body parts (1)
- ThyroidDocumented risk
Dried ao-nori is a notable iodine source per gram. Too much iodine can change how the thyroid works; ask a clinician if you have thyroid disease. This is about excess, not thyroid support.
Biomarkers (1)
- TSHPreliminary or mixed
In 49 regular seaweed eaters (species not named), TSH fell after six weeks without seaweed. This is not specific to this seaweed and is not proof of harm.
Documented risks and interactions (4)
- Ao-nori and iodine intake. Dried ao-nori is listed at 2,700 mcg iodine per 100 g, about 27 mcg per gram. The ATA says intake above 1,100 mcg a day is not recommended.
- Habitual seaweed eating, iodine and thyroid tests. In 49 regular seaweed eaters (species not named), TSH fell after six weeks without seaweed. People with thyroid disease should ask a clinician before eating seaweed often.
- Sodium in dried ao-nori. Dried ao-nori lists 8.1 g salt equivalent per 100 g (about 0.08 g per gram). Seasoned mixes and sauces were not measured in sources we read.
- Pregnancy, breastfeeding and seaweed iodine. The ATA encourages 220-250 mcg iodine a day in pregnancy and advises against iodine or kelp supplements above 500 mcg. We found no safe amount of ao-nori for pregnancy.
Frequently asked questions
What is the difference between ao-nori and nori?
Nori is dried purple laver (a red alga) sold as sheets. Ao-nori is a green alga sold as flakes or powder. [3][8] Their nutrients differ, and the B12 findings we read apply to nori, not ao-nori. [8]
How much iodine is in ao-nori?
The Japanese table lists 2,700 mcg per 100 g of dried ao-nori, about 27 mcg per gram. [2] A light sprinkle gives a small part of the 1,100 mcg adult upper limit quoted by the ATA, but frequent heavy use adds up. [6]
Does ao-nori contain vitamin B12?
The Japanese table lists 41.6 mcg per 100 g. [2] We cannot say whether that is active B12 in people, because the B12 review we read looked at purple laver (nori) only. [8] If you eat no animal foods, see the B12 claims guide.
Who should be careful with ao-nori?
People with thyroid disease or on thyroid medicine, and pregnant or breastfeeding women, should ask a clinician before eating seaweed often because of iodine. [6][7] Check mixed seasonings for allergens.
References
- Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. Standard Tables of Food Composition in Japan, item 09001 aosa, sun-dried (8th revised, 2023 supplement). Read 2026-10-24.
- MEXT. Item 09002 aonori, sun-dried (8th revised, 2023 supplement). Read 2026-10-24.
- MEXT. Standard Tables of Food Composition in Japan 2020 (8th revised), explanatory notes on algae. 2020. Read 2026-10-24.
- Lee Y, et al. Analysis and Risk Assessment of Total Iodine Content in Edible Seaweeds in South Korea. Foods 2025. Read 2026-10-24 (abstract; used for context only: sea tangle 2,432 mg/kg dry weight was the highest of five).
- Aakre I, et al. Impact of habitual seaweed consumption on iodine nutrition and thyroid function. Eur J Nutr 2026. Read 2026-10-24.
- American Thyroid Association. Statement on the potential risks of excess iodine ingestion and exposure. 2013, page updated 2024. Read 2026-10-24.
- NHS. Vitamins and minerals: Iodine. Read 2026-10-24.
- Watanabe F, et al. Vitamin B12-containing plant food sources for vegetarians. Nutrients 2014. Read 2026-10-24 (abstract via Europe PMC).
- Japan Ministry of Health, Labour and Welfare (e-JIM). Iodine page, seaweed iodine table. Read 2026-10-24.