The Possible Risks of Nori Seaweed

Is Nori Seaweed Safe to Eat?

Is Nori Seaweed Safe to Eat?
Everyday Health
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Updated on August 7, 2025
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A type of dried seaweed commonly featured in Japanese and Korean cuisine, nori is typically available in thin sheets that you cut or tear into smaller pieces. The smaller pieces then wrap around a bite-size portion of rice, as a garnish or in various sushi dishes. Nori is generally safe to eat in moderate amounts and offers numerous health benefits: Seaweed is low in calories, fat, and sugar, while also providing essential minerals and plant compounds.

However, excessive nori consumption may contribute to a high sodium or vitamin K intake. If you have underlying health problems that require close monitoring of your sodium or vitamin intake, consult with your medical provider regarding your dietary needs.

High Sodium Content

The body needs sodium to regulate how its nerves and muscles work and to maintain a healthy blood pressure.

 The Dietary Guidelines for Americans recommends 2,300 milligrams of sodium each day for adults over 18 years of age.

However, adults in the United States consume around 3,400 milligrams of sodium daily, putting them at risk of health complications, including high blood pressure. This, in turn, can cause issues with the heart, brain, kidneys, and eyes, including heart attacks, heart failure, kidney disease, stroke, and blindness.

Nori ingredients differ from one product to another.

 For example, one full sheet of roasted nori from Blue Dragon contains 15 milligrams of sodium.

 Another, from Gimme Seaweed, contains 5 milligrams.

 These amounts may not seem like much in the context of a 2,300-milligram daily value, but they can add up quickly. After all, you’ll rarely be eating nori on its own, but instead as part of a sushi roll.
When dining out in a Japanese restaurant, sodium consumption can add up further when you consider the nori, soy sauce, added salt, flavorings, and other items.

 Individuals on a low-sodium diet will need to restrict their sodium intake and may find it challenging to track the sodium in these individual elements, including nori.
However, if you’re preparing nori at home, you can check the nutrition label to get a sense of how much sodium it contains.

Rich in Vitamin K, Which Risks Medication Interactions

Seaweed is a good source of vitamin K.

 Vitamin K serves as an anticoagulant and protects against blood clotting in the arteries. This lets blood flow freely to the heart, lungs, and brain.

Drastic, sudden changes in your vitamin K intake may reduce the effectiveness of medications that also aim to reduce blood clots, such as warfarin, and increase the risk of blood clots and stroke.

 If you’re taking warfarin or another blood thinner, discuss nori with your doctor to determine how it can fit into your diet plan.

Can the Omega-3s in Nori Interact With Medications?

Docosahexaenoic acid (DHA) is a type of omega-3 fatty acid. While oily fish such as salmon, mackerel, herring, and sardines are familiar animal sources of DHA, seaweed is a good vegetarian alternative.

The Office of Dietary Supplements notes that omega-3 fatty acids, such as DHA, promote the proper development of the nervous system and support brain and eye health.

However, high doses of omega-3 fatty acids such as DHA may increase the effects of anticoagulant medications, leading to an increased risk of bleeding.

 That said, with the amount you’re likely to get from eating nori, interactions are very unlikely. Speak to a healthcare professional if you’re concerned about foods in your diet interacting with the medications you take.

Additional Health Concerns

Some types of seaweed, including nori, contain large quantities of iodine, which is crucial for the functioning of your thyroid gland but may cause health issues if you consume too much.

 You need around 150 micrograms of iodine daily.

 Two tablespoons of flaked nori seaweed, or around 5 grams, provides 116 micrograms, or 77 percent, of the recommended daily value.

 Keeping an eye on your nori consumption can mean you get the benefits of its iodine content without consuming too much.
If a seaweed cultivator grows seaweed in an area with arsenic, mercury, lead, or cadmium contamination, the seaweed might absorb these potentially toxic heavy metals in trace amounts.

 Although the presence of these in each serving would be tiny, if they’re present at all, these metals can build up in the body over time via a process known as bioaccumulation. Lead, cadmium, and arsenic have a particularly high capability for bioaccumulation.

The Takeaway

  • Nori is a type of dried seaweed that is low in calories and fat, and is generally safe and nutritious when eaten in moderation.
  • However, excessive intake can pose risks, such as high sodium and vitamin K content. Both are necessary for health, but high or changing intakes may affect individuals with specific dietary restrictions or those taking certain medications, including blood thinners.
  • Nori contains beneficial omega-3 fatty acids, which can also interact with certain medications — though the risk is minimal with the amount typically ingested from nori. However, it is always advisable to consult with healthcare professionals before making dietary changes, if you have concerns.
  • Environmental factors may lead to nori containing trace amounts of heavy metals like arsenic and lead, and it can also lead to excess iodine in your diet if you eat too much of it.
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
  1. Seaweed: A Tasty, Nutritious Snack. Harvard Health Publishing. August 19, 2024.
  2. Sodium. MedlinePlus. April 17, 2023.
  3. Dietary Guidelines for Americans 2020–2025. Department of Health and Human Services. December 2020.
  4. Sodium in Your Diet. U.S. Food and Drug Administration. March 5, 2024.
  5. Sushi Nori: Blue Dragon. Nutritionix. May 31, 2025.
  6. Organic Sushi Nori Sheets. Gimme Seaweed.
  7. Imamoto M et al. Salt Intake per Dish in the Japanese Diet: A Clue to Help Establish Dietary Goals at Home. Journal of Nutritional Science. December 15, 2021.
  8. Vitamin K: Fact Sheet for Health Professionals. National Institutes of Health: Office of Dietary Supplements. March 29, 2021.
  9. Rocha CP et al. Seaweeds as Valuable Sources of Essential Fatty Acids for Human Nutrition. International Journal of Environmental Research and Public Health. May 7, 2021.
  10. Omega-3 Fatty Acids: Fact Sheet for Health Professionals. National Institutes of Health: Office of Dietary Supplements. December 17, 2024.
  11. Daily Value on the Nutrition and Supplement Facts Labels. U.S. Food and Drug Administration. March 5, 2024.
  12. Iodine: Fact Sheet for Health Professionals. National Institutes of Health: Office of Dietary Supplements. November 5, 2024.
  13. Khandaker MU et al. Elevated Concentrations of Metal(loids) in Seaweed and the Concomitant Exposure to Humans. MDPI Foods. February 10, 2021.
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