Wakame: Nutrients, What Research Shows and Safety
Wakame as a food: iodine is the main safety point, USDA values for raw wakame, miso soup use, what research shows, arsenic and pregnancy notes, and the invasive-species background.
Content last updated . This page has not been medically reviewed.
Wakame is a brown seaweed, Undaria pinnatifida, native to Japan, Korea and parts of China. [6] It is a staple of Japanese and Korean cooking, best known as the soft green pieces floating in miso soup. [6] It is sold dried, salted, or fresh. People eat it for taste and for minerals, and sometimes for health claims. This page keeps the food apart from extracts and supplements, and apart from hype.
Read this first
- Iodine is the main safety point. Wakame holds much less iodine than kombu, but still a lot. One review lists 30 to 185 micrograms (mcg) of iodine per gram of dried wakame, versus 2,500 to 10,000 mcg per gram for kombu-type kelp. [2] The adult upper level is 1,100 mcg a day in the US and Canada, and 600 mcg a day for the European Food Safety Authority (EFSA). [2] [5]
- Amounts vary and labels rarely help. A Norwegian survey of 96 seaweed products found iodine varied hugely, and labeling of species and iodine was often inadequate or inaccurate. [3] In a UK survey, only 10% of 224 seaweed products stated their iodine content. [4]
- Thyroid disease, pregnancy, breastfeeding and infants: the American Thyroid Association (ATA) says people with thyroid disease, infants, older adults and pregnant or breastfeeding women are more susceptible to harm from excess iodine. [5] Ask your clinician; this page does not tell anyone to eat or avoid wakame.
- Arsenic: a small feeding study found urinary arsenic rose after volunteers ate wakame. [9] A review says most seaweed arsenic is in forms much less toxic than inorganic arsenic. [2]
- Evidence in one line: wakame is a tasty food with real iodine and mineral content. We found no human trial showing it treats or prevents a disease.
What is in it (USDA values)
The values below are for raw wakame (USDA FoodData Central item 170496, SR Legacy), which is mostly water (about 80 g of water per 100 g). [1] Dried wakame is a different form and holds far more per gram; do not mix the two. The serving column is the USDA household portion of 2 tablespoons (1/8 cup), 10 g. [1]
| Nutrient | Per 100 g raw | Per 2 tbsp (10 g) | % Daily Value per serving |
|---|---|---|---|
| Energy | 45 kcal | 4.5 kcal | not set |
| Protein | 3.03 g | 0.3 g | 1% |
| Fiber | 0.5 g | 0.05 g | 0% |
| Sodium | 872 mg | 87 mg | 4% |
| Calcium | 150 mg | 15 mg | 1% |
| Magnesium | 107 mg | 10.7 mg | 3% |
| Iron | 2.18 mg | 0.22 mg | 1% |
| Manganese | 1.4 mg | 0.14 mg | 6% |
| Copper | 0.284 mg | 0.028 mg | 3% |
| Folate (DFE) | 196 mcg | 19.6 mcg | 5% |
| Vitamin K | 5.3 mcg | 0.5 mcg | 0% |
% Daily Value uses the FDA 2016 Daily Values and was computed by us from the per-100-g numbers; values vary with harvest site, season and processing. USDA lists no iodine value for this food, and its vitamin B12 value of 0 does not tell us whether wakame has or lacks B12; see seaweed and vitamin B12 claims checked. [1] A review table puts wakame iodine at 30 to 185 mcg per gram of dry weight (it lists the species under green algae, but wakame is a brown seaweed). [2]
Plant compounds: the sources we read for this page did not measure fucoxanthin, fucoidan or other compounds in wakame as eaten, so we make no claim about them. Many web claims about seaweed compounds come from lab or animal work. [8]
What research says
| Health goal | What the sources found | Strength of evidence | What was studied |
|---|---|---|---|
| Iodine intake | Seaweed raises iodine intake. In a feeding study of 11 volunteers, urinary iodine rose after eating nori, kombu or wakame, and most after kombu. [9] | Established for raising iodine intake (a measure, not a health result) | Small feeding study, whole seaweeds |
| Arsenic exposure | In the same study, total urinary arsenic rose, with the largest effect after wakame. The abstract gives no health outcome. [9] | Established as an exposure measure; health effect not shown | 11 volunteers |
| Heart disease, diabetes, weight | A 2019 narrative review says more evidence from human intervention studies is needed to confirm benefits of seaweed. [8] | Insufficient evidence | Reviews of whole seaweeds, extracts and seaweed foods mixed together |
| Thyroid support | Iodine is needed for thyroid hormones, but excess can harm. Nothing we read shows wakame improves thyroid health. [5] [2] | No good evidence of benefit found in the sources we read | Not applicable |
| Cancer, antiviral, "detox" | Proper evidence not found in the sources we read. | Lab or animal only at best | Not applicable |
Eaten as food vs taken as extract or supplement. The studies above concern the seaweed as food or seaweed in general. Extracts and capsules are different products and are covered on their own pages, such as fucoxanthin.
Invasive species note. Wakame is also a well-known marine invader. The Global Invasive Species Database calls it an opportunistic weed that spreads mainly by fouling ship hulls, and says its impacts are not well understood. [6] A 2017 review found it established in 13 countries, with minimal ecological impact in most places, and management had little success. [7] This is about wild populations, not about the safety of the farmed seaweed sold as food.
How much is a normal serving
The USDA household portion is 2 tablespoons (10 g) of raw wakame, about 4.5 kcal. [1] That is information from the USDA data, not a prescription. The review table estimates that 2 to 6 g of dried wakame would reach the 150 mcg iodine intake recommended for adults, based on its 30 to 185 mcg per gram range. [2] Miso soup uses a small pinch of rehydrated dried wakame; for miso itself see miso. We found no source measuring how much iodine is lost when dried wakame is soaked or boiled, and that review says cooking losses must be considered but gives no figure. [2]
Safety, allergy and medicines
- Iodine excess. Excess iodine can cause both overactive and underactive thyroid in some people. [2] [5] The ATA advises against iodine and kelp supplements giving more than 500 mcg a day. [5] Wakame is not a supplement, but regular large amounts add up with other sources.
- Pregnancy and breastfeeding. The ATA lists upper limits for pregnancy and lactation of 500 to 1,100 mcg a day, depending on the body. [5] LactMed says iodine passes actively into breast milk and that some sources recommend against seaweed while breastfeeding because of iodine and possible heavy metals. [10] See what official bodies advise.
- Arsenic and metals. Seaweeds take up arsenic; most is in arsenosugars, much less toxic than inorganic arsenic. [2] We did not find a source with a specific inorganic-arsenic figure for wakame, so we cannot say how much. See heavy metals and seaweed.
- Sodium. USDA lists 872 mg sodium per 100 g raw wakame. [1] Salted wakame and miso soup add more; we did not read a source with figures for them.
- Vitamin K and warfarin. USDA lists 5.3 mcg vitamin K per 100 g raw wakame, a small amount. [1] We did not find a source that tested wakame with warfarin. If you take a blood thinner, keep your diet steady and ask your clinician; see medicines and conditions.
- Allergy. Seaweed allergy is not covered in the sources we read for this page. For trouble breathing or swelling of the face or throat after eating, call 911 (or your local emergency number).
Choosing, storing and food safety
- Dried, salted and fresh wakame are different forms. Iodine per gram is far lower in the wet forms because of water. [1] [2]
- Because labels often omit iodine and species, [3] [4] ask the seller or choose a product with a stated amount if you eat seaweed often.
- Food safety rules for ready-to-eat seaweed foods are on seaweed salad; buying and storing tips are on how to buy, prepare and store seaweed.
Related pages
Health connections for Wakame
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.
Wakame and iodine intake
Clinically supportedWakame holds much less iodine than kombu, but a review lists 30 to 185 mcg per gram of dried wakame, enough that 2 to 6 g dried reaches the adult 150 mcg recommended intake.
Supplements: This is about a raised intake measure, not a disease outcome; labels rarely state iodine.
Wakame in miso soup and cooking
Established roleA staple of Japanese and Korean cooking; USDA lists raw wakame as low in energy (45 kcal per 100 g) with 872 mg sodium per 100 g.
Supplements: Not a supplement topic.
Minerals in raw wakame
Established roleUSDA lists per 100 g raw: magnesium 107 mg, calcium 150 mg, manganese 1.4 mg, folate 196 mcg DFE. A 10 g portion gives small percentages of Daily Values.
Supplements: Normal portions are small, so mineral contribution is modest.
Wakame for heart disease, diabetes or weight: evidence
Preliminary or mixedA 2019 narrative review says more evidence from human intervention studies is needed to confirm benefits of seaweed.
Supplements: No wakame-specific trial was found in the sources read.
Wakame as an invasive species
Lab or animal research onlyThe Global Invasive Species Database calls Undaria an opportunistic weed spreading mainly by hull fouling; a 2017 review found it established in 13 countries with minimal ecological impact in most places.
Supplements: Not a health topic.
Connected topics
Open a group to see how each topic connects and how strong the evidence is.
Body systems (1)
- Endocrine SystemDocumented risk
Iodine in wakame supports thyroid hormones, but too much can disturb the thyroid. Seaweed iodine varies widely.
Body parts (1)
- ThyroidDocumented risk
Excess iodine from seaweed can cause overactive or underactive thyroid in some people; people with thyroid disease are more susceptible.
Root causes (1)
- Heavy Metal ExposureDocumented risk
Urinary arsenic rose after wakame in a small feeding study; most seaweed arsenic is the less toxic organic kind per a review.
Conditions & symptoms (3)
- GoiterDocumented risk
Excess iodine from seaweed may cause thyroid problems including goiter in susceptible people, per a review.
- HyperthyroidismDocumented risk
Excess iodine from seaweed can lead to overactive thyroid in some people.
- HypothyroidismDocumented risk
Excess iodine can lead to underactive thyroid in some people.
Documented risks and interactions (4)
- Iodine excess, thyroid disease and wakame. Too much iodine can cause overactive or underactive thyroid in some people. The American Thyroid Association says people with thyroid disease, infants, older adults and pregnant or breastfeeding women are more susceptible.
- Arsenic from wakame. In a feeding study of 11 volunteers, urinary arsenic rose after eating wakame, the largest effect among the seaweeds tested. A review says most seaweed arsenic is in forms much less toxic than inorganic arsenic.
- Wakame and breastfeeding. LactMed says iodine passes actively into breast milk and that some sources recommend against seaweed while breastfeeding because of iodine and possible heavy metals.
- Wakame, sodium and salted forms. USDA lists 872 mg sodium per 100 g raw wakame; salted wakame and soups add more but no figure was found in the sources read.
Frequently asked questions
Does wakame have a lot of iodine?
More than most foods, but far less than kombu. One review lists 30 to 185 mcg per gram dried wakame, against 2,500 to 10,000 mcg per gram for kombu-type kelp. [2] Amounts vary by product. [3]
Is wakame safe if I have a thyroid condition?
We cannot say for you. The ATA says people with existing thyroid disease are more susceptible to harm from excess iodine. [5] Ask your clinician.
Is wakame in miso soup a concern?
The soup uses small amounts of rehydrated dried wakame. We found no source measuring iodine in a bowl of miso soup, so we make no claim either way.
Does wakame contain arsenic?
Seaweeds take up arsenic, mostly as forms much less toxic than inorganic arsenic. [2] In a small feeding study, urinary arsenic rose after wakame. [9]
Is wakame an invasive species?
Wild Undaria is listed as invasive in many coastal areas. [6] [7] Farmed wakame sold as food is a separate question this page does not judge.
References
- USDA FoodData Central. Seaweed, wakame, raw (FDC 170496), SR Legacy. April 2018 release. Read 2026-10-24.
- Smyth PPA. Iodine, Seaweed, and the Thyroid. Eur Thyroid J. 2021;10(2):101-108. Read 2026-10-24.
- Aakre I, et al. Commercially available kelp and seaweed products - valuable iodine source or risk of excess intake? Food Nutr Res. 2021;65. PubMed 33889064 (abstract via Europe PMC). Read 2026-10-24.
- Bouga M, Combet E. Emergence of Seaweed and Seaweed-Containing Foods in the UK. Foods. 2015;4(2):240-253 (abstract via Europe PMC). Read 2026-10-24.
- American Thyroid Association. ATA Statement on the Potential Risks of Excess Iodine Ingestion and Exposure. Read 2026-10-24.
- IUCN Global Invasive Species Database. Undaria pinnatifida. Read 2026-10-24.
- Epstein G, Smale DA. Undaria pinnatifida: a case study to highlight challenges in marine invasion ecology and management. Ecol Evol. 2017. Read 2026-10-24.
- Cherry P, et al. Risks and benefits of consuming edible seaweeds. Nutr Rev. 2019;77(5):307-329 (abstract via Europe PMC). Read 2026-10-24.
- Exposure to iodine, essential and non-essential trace element through seaweed consumption in humans. 2024. PubMed 38871780 (abstract via Europe PMC). Read 2026-10-24.
- Drugs and Lactation Database (LactMed). Seaweed. Record via Europe PMC. Read 2026-10-24.