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Types of seaweed are sorted in this guide by color group: red, brown and green algae. A 2019 review in Nutrition Reviews calls edible seaweeds macroalgae, and FDA’s food regulations list brown algae and red algae species by name. USDA SR Legacy data hold five raw seaweed entries that this guide compares: kelp, laver, wakame, agar and Irish moss. In USDA data, 100 grams of raw laver list 5.8 grams of protein, the most of the five, and 100 grams of raw wakame list 872 milligrams of sodium.
Peptide Labs does not sell foods. This article is general nutrition information, not medical advice.
Key Takeaways
- NOAA describes seaweed as the common name for countless species of marine plants and algae, in colors of red, green, brown and black.
- FDA's food regulations list Porphyra species among red algae and Laminaria species and Undaria pinnatifida among brown algae; the 2019 review identifies them as nori, kombu and wakame.
- Per 100 grams raw in USDA data, laver lists the most protein (5.8 grams), Irish moss the most iron (8.9 milligrams) and wakame the most sodium (872 milligrams).
- NIH ODS says the iodine amounts in different seaweed species vary greatly; USDA SR Legacy holds no iodine value for these five entries.
Edible seaweed: what the federal sources say
NOAA’s National Ocean Service describes seaweed as the common name for countless species of marine plants and algae that grow in the ocean as well as in rivers, lakes and other bodies of water, and notes that most come in colors of red, green, brown and black. The review by Cherry and colleagues in Nutrition Reviews uses the same three main groups when it describes edible seaweed: brown, red and green. In Japan, the review states, approximately 20 different types of seaweed are consumed, the majority being wakame (Undaria), kombu (Laminaria) and nori (Porphyra).
FDA’s food regulations name two of the groups. FDA’s rule 21 CFR 184.1120 says brown algae are seaweeds of named species, among them several Laminaria species, Macrocystis pyrifera and Undaria pinnatifida, harvested principally in coastal waters of the northern Atlantic and Pacific oceans. FDA’s rule 21 CFR 184.1121 says red algae are seaweeds of the species Gloiopeltis furcata, Rhodymenia palmata and several Porphyra species. FDA says both are dried and ground or chopped for use in food.
Types of seaweed ranked by USDA values per 100 grams
Values are per 100 grams of the raw seaweed as USDA SR Legacy lists them, ranked by protein; the ranking is an editorial choice. Raw values are used because USDA has no dried entry for most of these seaweeds. For scale, FDA’s Daily Value for sodium on a label is 2,300 milligrams (21 CFR 101.9). Packaged seaweed products can differ from these raw entries, so check the Nutrition Facts label, which FDA rules require to show sodium.
| Food (USDA FDC ID) | Amount | Calories | Protein | Fiber | Calcium | Iron | Magnesium | Sodium |
|---|---|---|---|---|---|---|---|---|
| Laver, raw (168458) | 100 g | 35 | 5.8 g | 0.3 g | 70 mg | 1.8 mg | 2 mg | 48 mg |
| Wakame, raw (170496) | 100 g | 45 | 3.0 g | 0.5 g | 150 mg | 2.2 mg | 107 mg | 872 mg |
| Kelp, raw (168457) | 100 g | 43 | 1.7 g | 1.3 g | 168 mg | 2.9 mg | 121 mg | 233 mg |
| Irish moss, raw (168456) | 100 g | 49 | 1.5 g | 1.3 g | 72 mg | 8.9 mg | 144 mg | 67 mg |
| Agar, raw (169280) | 100 g | 26 | 0.5 g | 0.5 g | 54 mg | 1.9 mg | 67 mg | 9 mg |
In USDA data, raw kelp lists the most calcium of the five, 168 milligrams per 100 grams, and Irish moss the most iron and magnesium, 8.9 and 144 milligrams. Wakame lists 872 milligrams of sodium per 100 grams in USDA data, against 233 for kelp and 9 for agar. All five list between 26 and 49 calories per 100 grams in USDA data. Our low sodium foods guide explains how FDA defines sodium label terms.
Red algae in FDA rules and the review: laver, dulse and agar
- Nori: the review identifies Porphyra species as nori, and FDA’s red algae rule lists several Porphyra species, among them Porphyra tenera, which a study cited in the review calls laver, the name of the USDA raw entry. Our nori guide covers the dried sheets.
- Dulse: the review names Palmaria palmata (dulse) with nori as red seaweeds with a high protein content. USDA SR Legacy has no dulse entry, so dulse is not in the table.
- Agar: FDA’s rule 21 CFR 184.1115 describes agar-agar as a dried, colloidal polysaccharide extracted from one of a number of related species of red algae (class Rhodophyceae). USDA lists raw agar at 26 calories per 100 grams, the fewest in the table.
- Red seaweed fibers: the review states that red seaweeds contain agar, carrageenan, porphyran and xylan.
Brown algae in FDA rules and the review
- Kombu: the review identifies kombu as Laminaria, and FDA’s brown algae rule lists Laminaria digitata, Laminaria japonica and several other Laminaria species. Our kelp guide covers kombu with the other kelps.
- Wakame: the review identifies wakame as Undaria, and FDA’s brown algae rule lists Undaria pinnatifida. USDA lists raw wakame at 872 milligrams of sodium per 100 grams.
- Giant kelp: FDA’s brown algae list also names Macrocystis pyrifera.
- Brown seaweed fibers: the review states that brown seaweeds contain alginate, laminarin and fucoidan polysaccharides.
Green algae in the review, and two USDA entries outside the groups
The review states that green seaweeds contain ulvan, xylan and cellulose. USDA SR Legacy holds no green seaweed entry, and neither FDA rule lists a green species, so this guide has no USDA values to show for that group.
USDA lists Irish moss as a raw seaweed entry; it appears on neither of FDA’s two algae lists, so this guide does not place it in a color group. USDA also files spirulina under the same seaweed heading. FDA’s color additive rule for spirulina extract (21 CFR 73.530) says it is made from the dried biomass of Arthrospira platensis, a species that is on neither FDA algae list, so spirulina is left out of the table here.
Iodine: what NIH ODS says
The NIH Office of Dietary Supplements (ODS) names seaweed, such as kelp, nori, kombu and wakame, among the food sources of iodine. ODS adds that the iodine amounts in different seaweed species vary greatly, and that commercially available seaweeds in whole or sheet form range from 16 to 2,984 micrograms of iodine per gram. In the ODS food table, 2 tablespoons of dried, flaked nori (5 grams) list 116 micrograms, or 77% of the FDA Daily Value.
The same ODS fact sheet has a section on health risks from excessive iodine. USDA SR Legacy holds no iodine value for the five seaweeds in the table, so this guide cannot rank them by iodine. Our foods high in iodine guide shows the ODS food values, and anyone who has been told to watch iodine should ask a healthcare provider before eating seaweed often.
Where these algae show up in foods, per FDA and NOAA
NOAA notes that nori is the seaweed wrapped around a sushi roll; our sushi guide covers that dish. FDA lists agar-agar as an ingredient used in foods such as baked goods and confections as a stabilizer and thickener, and the review notes that alginate, carrageenan and agar have been used for decades to thicken and stabilize food. Our miso guide covers a soup often served with seaweed.
Food first: what this list does not cover
This list is about food. It gives no intake target: USDA publishes content data and FDA sets Daily Values for labels, and these are official reference facts, not a target for any reader. The list makes no health promises. Each USDA value describes one food entry, and packaged seaweed products can differ. Check the label, and ask a healthcare provider about your own needs, especially if you take medicines or have a health condition.
Frequently Asked Questions
What are the main types of seaweed?
Red, brown and green algae. The 2019 review uses those three groups, and FDA’s food regulations list red algae such as Porphyra species and brown algae such as Laminaria species and Undaria pinnatifida.
What is agar made from?
FDA’s rule 21 CFR 184.1115 describes agar-agar as a dried, colloidal polysaccharide extracted from one of a number of related species of red algae (class Rhodophyceae).
Which raw entry ranks first in the USDA table?
Laver, at 5.8 grams of protein per 100 grams raw in USDA data, followed by wakame at 3.0 grams and kelp at 1.7 grams.
Does USDA list iodine for these entries?
No. USDA SR Legacy holds no iodine value for the five raw entries; NIH ODS lists 116 micrograms for 2 tablespoons of dried, flaked nori and says iodine amounts vary greatly between species.
Why are some USDA entries left out of the table?
USDA files spirulina under the same heading, but FDA’s color additive rule describes spirulina extract as made from Arthrospira platensis, which is on neither FDA algae list, so this guide leaves it out; our spirulina guide covers it.
Questions about a label? Contact us or read our Buyer’s Guide. Food comes first; follow the label and ask a healthcare provider before starting a supplement, especially if you take medicines, are pregnant or have a health condition. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Last reviewed October 2026.
Related guides: Types of Oats: Groats, Steel-Cut, Rolled and Instant, Nori and Seaweed: USDA Nutrition, Benefits, Iodine and Safety, Kelp: USDA Nutrition, Benefits, Iodine and Who Should Be Careful.