Health Benefits of Seaweed

Medically Reviewed by Poonam Sachdev on September 19, 2022
4 min read

Seaweed is a general term that refers to a number of algae and marine plants that grow along rocky shorelines around the world. There are many different types, including red (Rhodophyta), green (Chlorophyta), blue-green, and brown (Phaeophyceae). Some of the most common types of edible seaweeds include:

  • Wakame
  • Dulse
  • Kombu
  • Kelp
  • Sea lettuce
  • Nori
  • Arame
  • Chlorella

While seaweeds grow in all different areas of the world, they’re most prevalent in Asian cuisines, where they’re featured in sushi, salads, soups, and stews.

In prehistoric times, seaweed was an important part of coastal peoples’ diets. Today, more than 145 varieties are used around the world.

While it doesn’t have the same popularity in the United States as it does in Asian countries, people are beginning to recognize that seaweed is a nutritious addition to the diet and provides several health benefits.

Seaweed is an excellent source of iodine, a vital trace mineral that plays a critical role in thyroid health. The body doesn’t make iodine on its own, so you need to get it from food sources or supplements. 

Health benefits of seaweed include:

Improves thyroid function.

Your thyroid plays a crucial role in your overall health, and iodine plays a vital role in its ability to function properly. Insufficient iodine means that your thyroid can’t make enough thyroid hormone (a condition known as hypothyroidism), which regulates many bodily functions, including metabolism. If you don’t get enough iodine, you may develop a goiter, a visible enlargement of your thyroid. Iodine deficiency can also impact children during development, both in the womb and during early childhood.

May improve gut health.

Seaweed has carrageenans, agars, fucoidans, which act as prebiotics, non-digestible fibers that feed the healthy bacteria in your digestive tract. Sulfated polysaccharides (sugars found in seaweed) help to increase the growth of the good bacteria and increase the short-term fatty acids that keep the lining of your gut healthy.

Improves heart health.

Some studies show that seaweed intake may help to reduce blood pressure. It may also help to reduce LDL cholesterol and total cholesterol levels. Results of human studies are promising, but more research is needed. 

Stabilizes blood sugar levels.

Brown seaweed contains fucoxanthin, an antioxidant that gives the vegetable its color. The antioxidant may play a role in helping to improve blood sugar control and reducing your risk of developing type 2 diabetes.

May boost your immune health. Some studies show that seaweed may help to boost your immune system by fighting viruses and preventing them from getting into your system. More studies are needed, however. 

May reduce cancer risk. Adding seaweed to your diet may help to reduce your risk of developing certain types of cancer. It may decrease estrogen levels, which may reduce the risk of breast cancer. Again, there are very few human studies available, so more research is necessary.  

While the nutrition content of seaweed varies based on where it grows and what type it is, they all contain a healthy vitamin and mineral profile. Most seaweeds contain nutrients such as:

  • Vitamin A
  • Vitamin B1
  • Vitamin B2
  • Vitamin C
  • Vitamin E
  • Vitamin K
  • Calcium
  • Folate
  • Potassium
  • Iron
  • Manganese
  • Copper

Seaweed contains many antioxidants in the form of certain vitamins (A, C, and E) and protective pigments. It has a decent amount of iodine, a trace mineral vital for the health and function of the thyroid. Some seaweeds, such as purple laver, contain a good amount of B12 as well.

Nutrients Per Serving

A 2-tablespoon serving of wakame seaweed has:

  • Calories: 5
  • Protein: 0 grams
  • Fat: 0 grams
  • Carbohydrates: 1 gram
  • Fiber: 0 grams
  • Sugar: 0 grams

Things to Watch Out For

Eating fresh seaweed is generally considered safe for most people. While the plant offers many health benefits, there are a few things to watch out for:

Too much iodine. While iodine is a vital trace mineral for thyroid health, too much can have the opposite effect. 

May interfere with certain medications. Seaweed contains a high amount of potassium, which can be harmful to individuals with kidney disease. Seaweed also contains vitamin K, which could interfere with blood-thinning medications such as Warfarin. 

Some varieties may have high levels of heavy metals. Some varieties of seaweed may contain high levels of arsenic, cadmium, mercury, or lead, depending upon how they’re grown. The FDA regulates the heavy metals in fresh seaweed, but not supplements. 

Many grocery stores carry some forms of dried seaweed. You may find dried seaweed snacks, nori for sushi, or dried dulse flakes. Many Asian food stores carry a greater variety of dried and fresh seaweed products. 

There are many ways to add seaweed into your diet, including:

  • Make a soup broth dried kelp or kombu
  • Mix fresh arame and wakame with vinegar, sesame oil, scallions, and garlic for a seaweed salad
  • Top meals with a mix of ground nori, kombu, dulse, salt, black pepper, and sesame seeds
  • Snack on dried nori
  • Add kombu to cooked beans
  • Make homemade sushi
  • Make a vegan “tuna” salad with chickpeas, vegan mayonnaise, celery, red onion, salt, pepper, and dulse flakes

Show Sources


BBC News: “Seaweed: Should People Eat More of It?”

University of Michigan-Michigan Medicine: “Thyroid Hormone Production and Function.”

Sultan Qaboos University Medical Journal: “Health Consequences of Iodine Deficiency.”

Marine Drugs: “Prebiotics from Marine Macroalgae for Human and Animal Health Applications.”

International Journal of Biological Macromolecules: “Digestibility of Sulfated Polysaccharide from the Brown Seaweed Ascophyllum nodosum and Its Effect on the Human Gut Microbiota In Vitro.”

Journal of Clinical Biochemistry and Nutrition: “Clinical Effects of Brown Seaweed, Undaria pinnatifida (Wakame), on Blood Pressure in Hypertensive Subjects.”

Journal of Nutritional Science: “Reduction of HbA1c Levels by Fucoxanthin-Enriched Akamoku Oil Possibly Involves the Thrifty Allele of Uncoupling Protein 1 (UCP1): A Randomized Controlled Trial in Normal-Weight and Obese Japanese Adults.”Current Medicinal Chemistry: “Phenolic Compounds from Edible Algae: Bioactivity and Health Benefits.”

PloS One: “Aqueous Extracts of Marine Brown Alga Lobophora variegate Inhibit HIV-1 Infection at the Level of Virus Entry into Cells.”

Journal of Applied Phycology: “The Consumption of Seaweed as a Protective Factor in the Etiology of Breast Cancer: Proof of Principle.”

Nutrition Reviews: “Nutritional Value of Edible Seaweeds.”

Nutrients: “Vitamin B12-Containing Plant Food Sources for Vegetarians.”

ESHA Research, Inc., Salem, Oregon.

Endocrine Journal: “Suppression of Thyroid Function During Ingestion of Seaweed “Kombu” (Laminaria japonoca) in Normal Japanese Adults.”

Journal of Medical Case Reports:Palmaria pamata (Dulse) as an Unusual Maritime Aeteology of Hyperkalemia in a Patient with Chronic Renal Failure: A Case Report.”

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