Nori and Seaweed: USDA Nutrition, Benefits, Iodine and Safety

Nori is the thin, dark seaweed sheet wrapped around sushi and sold as roasted seaweed snacks. It is made from red algae that USDA FoodData Central lists as laver, and nutritionally it is a low-calorie food with some plant protein, vitamin C, vitamin A, folate and manganese, plus iodine. The catch with nori and every other seaweed is variability: the NIH Office of Dietary Supplements (ODS) notes that iodine content differs greatly from one seaweed to the next. Below are the USDA nori nutrition numbers, how nori compares with kelp and wakame, which seaweed benefits are actually supported, and who should be careful.

Peptide Labs does not sell nori or seaweed snacks. This article is general nutrition information, not medical advice.

Nori nutrition: what USDA data show

USDA SR Legacy has one entry for this seaweed, raw laver (FDC 168458), and lists 10 raw sheets at 26 grams. There is no separate entry for the dried, roasted sheets sold for sushi. Drying removes water, so nutrients are more concentrated per gram in dried nori, and seasoned snacks add oil and salt. Use the package Nutrition Facts for the product you actually eat. The %DV column uses FDA Daily Values and refers to the 100-gram amount.

Two points stand out. First, nori is mostly water and air by weight in the form people eat, so the amounts in a few sheets are modest even when the per-100-gram percentages look high. Second, plain nori is low in sodium in the USDA data, but flavored seaweed snacks are a different product, so check the label if you are watching salt (see our low sodium foods guide). USDA also lists no vitamin B12 for raw laver. Online claims that nori is a vegan B12 source are not a safe bet; our B12 foods guide covers fortified options. For iron, nori adds a little non-heme iron; our iron foods list has richer sources.

Iodine in nori and other seaweed

Iodine is the nutrient that makes seaweed different from land vegetables. ODS explains that iodine is an essential part of the thyroid hormones T4 and T3, and lists seaweed, including kelp, nori, kombu and wakame, among food sources along with fish, other seafood and eggs. In the ODS food table, 2 tablespoons of dried, flaked nori (about 5 grams) provide about 116 micrograms of iodine, or 77% of the Daily Value.

That single number hides a lot of spread. ODS cites a 2004 study in the journal Thyroid that tested commercially available seaweeds sold whole or as sheets and found iodine concentrations from 16 to 2,984 micrograms per gram, depending on species and product. ODS also points out that Nutrition Facts labels usually do not list iodine unless the manufacturer added it, so a nori package will rarely tell you how much is inside. Brown seaweeds such as kelp are covered in our kelp guide.

Seaweed benefits: what is and is not known

The seaweed benefits that hold up are nutritional. Nori is low in calories and fat, adds vitamin C, vitamin A, folate and manganese, and contributes iodine, a nutrient some people fall short on. ODS says the general US population appears to get enough iodine, but people who do not use iodized salt, pregnant people, vegans and people who eat little dairy, seafood or eggs are more likely to fall short. For those groups, a food source can matter, although the variability above makes seaweed an unreliable way to hit any particular number.

Many other claims go well beyond the evidence. Most articles promoting seaweed for weight loss, blood sugar, detox or a thyroid boost lean on laboratory or animal studies of single compounds, not on trials of people eating nori. We found no good basis for promising any of those outcomes, and seaweed is not a substitute for medical care for a thyroid condition.

Nori vs kelp, wakame and other seaweeds

The table compares raw seaweeds in USDA SR Legacy per 100 grams. Values for dried products are higher per gram because the water is gone, and none of these entries include iodine.

Nori has the most protein of the true seaweeds in this list and the least sodium after agar, while wakame is far saltier per 100 grams. Irish moss is the seaweed sold as sea moss; see our sea moss guide for its iodine and contamination questions. USDA files spirulina under seaweed, but it is a cyanobacterium; our spirulina and chlorella guides cover those algae.

Is seaweed healthy? Who should be careful

For most people, nori in normal food amounts is a nutritious addition. The cautions are mostly about iodine and about which seaweed you are buying.

• Thyroid conditions. ODS notes that people with autoimmune thyroid disease may react to iodine intakes considered safe for others. Ask your clinician before eating seaweed often.
• Antithyroid medicines. ODS lists an additive effect between iodine and medicines such as methimazole that could cause hypothyroidism.
• Pregnancy and breastfeeding. Iodine needs are higher, but so is the stake in avoiding excess. Talk to your OB-GYN; our iodine guide covers the professional recommendations.
• Seasoned snacks. Added salt and oil change the numbers, so read the label.
• Vitamin K and warfarin. Raw laver is low in vitamin K in USDA data, but kelp is higher; see our vitamin K foods guide.

Upper limit for iodine

The Food and Nutrition Board set a Tolerable Upper Intake Level for iodine of 1,100 micrograms a day for adults, from food and supplements combined, according to the ODS fact sheet. It is a regulatory reference, not a goal. ODS lists goiter, raised TSH, hypothyroidism, iodine-induced hyperthyroidism and thyroiditis among the effects of excess iodine. At the top of the seaweed range ODS cites, a single gram of seaweed would hold more iodine than that adult upper limit, which is why steady, heavy seaweed eating deserves a conversation with a clinician.

Arsenic and hijiki

Hijiki (Sargassum fusiforme) is a different, brown seaweed sold as dark strands. A 2012 review in Regulatory Toxicology and Pharmacology notes that the UK Food Standards Agency and its counterparts in other countries warned consumers not to eat hijiki because it contains large amounts of inorganic arsenic. A 2019 Japanese duplicate-diet study of 104 children and 101 pregnant women found that frequent hijiki eaters had higher inorganic arsenic intake. Nori is not hijiki, but it is a good reason to know which seaweed you are buying. Rice is another dietary arsenic source; see our brown rice guide.

Enjoying nori

Nori works as a sushi wrap, a crumbled topping for rice, eggs or soup, or a crisp snack. Plain sheets keep sodium low; seasoned versions vary. Because labels rarely show iodine, variety in the seaweeds you eat and attention to how often you eat them are sensible habits, and anyone with a thyroid condition should get personal advice. If you take a supplement that lists kelp or iodine, count it too, and look for third-party testing.

Frequently Asked Questions

Questions about a label? Contact us or read our Buyer’s Guide. Food comes first; follow the label and ask a healthcare provider before adding seaweed products or supplements, especially if you have a thyroid condition, take medicines or are pregnant. 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: Kelp: USDA Nutrition, Benefits, Iodine and Who Should Be Careful, Iodine Supplement Guide: Deficiency, Kelp and Thyroid Safety, Sea Moss: Benefits, Iodine, Heavy Metals and Sea Moss Gel Safety.