✓ Evidence Based

Seaweed: Facts, Nutrition, Benefits, Risks & More

Seaweed holds many of the essential vitamins and nutrients our body needs to thrive (1). It’s high in many B vitamins, vitamin A, and vitamin C (2). Research suggests that including seaweed in your diet may support thyroid health and weight management and may also help manage diabetes (3).

What is seaweed?

Seaweed includes various types of algae and sea plants. These organisms are usually found in oceans and seas. Many types of seaweed found in oceans are usually safe for consumption, but they should be properly identified and prepared to ensure they are free from toxins.

Edible seaweed is typically categorized according to color. The main colors include green, blue-green, red, and brown. Seaweed is also categorized by size, which can include algae as small as a microscopic phytoplankton up to towering kelp.

Seaweed is the primary form of food for many sea creatures. It has also been a staple food in some cuisines around the world, particularly the Japanese and Chinese cuisines.

Common types of edible seaweed

Seaweed is a nutritious ingredient that has found its way into different dishes worldwide. Let’s take a look into some of the most common types of edible seaweed used in cooking:

  • Kombu: Kombu is a variety of kelp. This type of seaweed is popular in East Asia. Kombu is mostly used in Japanese cuisine, where it serves as a main ingredient in dashi. Dashi is a popular soup stock that is used to make ramen and miso soup.
  • Wakame: This plant is known for providing a habitat for many sea creatures. Wakame, also referred to as sea mustard, has a silky and smooth texture. It’s a dark green seaweed that is typically used in miso soup. This seaweed is known for its rich omega-3 content and delicious sweet taste (4).
  • Dulse: Known for its unique bacon taste, Dulse is a popular snack in Canada. This seaweed is harvested from the cold northern waters of the Atlantic and Pacific. This reddish seaweed is usually cooked until crispy and enjoyed as a snack.
  • Nori: Enjoyed in many parts of the world, nori is commonly used for wrapping sushi rolls. Nori has a deep purplish-red color when being harvested but quickly turns into a dark green color after getting dried. This type of seaweed is usually used dry and compressed in sushi rolls or in powder form to complement dishes like yakisoba and okonomiyaki.
  • Irish Moss: Native to the Atlantic shorelines, this purplish red algae looks just like miniature trees due to its unique branching structure. Irish moss is rich in carrageenan, which is a natural thickening agent. This makes it perfect to add to desserts like ice cream and tapioca.
  • Hijki: This brown seaweed is typically found in rocky shorelines in Japan, China and Korea. Its appearance resembles that of thin twigs and is usually used in stir-fries or served with fish.
  • Sea Lettuce: This algae is commonly found alongside coastlines. It’s a type of edible blue-green nori that is used in a variety of dishes due to its nutritional value.

    Because of its diverse use in the culinary world, seaweed not only adds a unique taste to dishes but it also offers a wide range of health benefits.

Nutrition of Seaweed

Seaweed is packed with nutrients such as vitamins A, C and E (1). This ingredient is most mostly notable for its high iodine content (5, 6). A 20 grams serving of seaweed (Ingredients: Wakame, Kelp, Laver) contains nutrients including (7):

  • Calories: 8.2
  • Carbohydrates: 1.59 grams
  • Protein: 0.7 grams
  • Fat: 0.1 grams
  • Sugars: 0.12 grams
  • Fiber: 0.14 grams
  • Vitamin C: 3.0 mg (3.33% daily value DV)
  • Sodium: 76.8 mg (3.34% DV)
  • Copper: 0.05 mg (5.11% DV)
  • Riboflavin: 0.06 mg (4.31% DV)

It’s important to keep in mind that the nutritional value varies slightly depending on the type of seaweed.

Health Benefits of Seaweed

Seaweed can be beneficial whether it’s consumed or taken as a dietary supplement. Let’s cover some of the health benefits it’s well-known for:

May Improve Heart Health

Many of the nutrients found in seaweed may contribute to cardiovascular health (8, 9, 10. It a good source of long-chain omega-3 fatty acids and soluble fiber (11, 1). Both components are known for promoting heart health.

Studies have found that regular seaweed consumption among children and adults can lead to decreased blood pressure levels (12, 13, 3). Although the findings are promising, more human studies are needed in order to come to better conclusions.

According to animal studies, some nutritional compounds found in seaweed such as sulfated polysaccharides may help reduce “bad” (LDL) cholesterol levels (14).

Provides Thyroid Support

The thyroid gland is responsible for the production of certain hormones that regulate metabolism, mood, and other bodily functions. Iodine consumption is important for the thyroid to function properly. Due to its high iodine content, seaweed is highly beneficial for thyroid support (15, 16).

Here’s the average Iodine content of some common dried seaweeds (17, (18):

  • Kombu: 2581 mcg per gram (1720.7% of the RDI)
  • Wakame: 139.5 mcg per gram (93% of the RDI)
  • Nori: 37.6 mcg per gram (25.1% of the RDI)
  • Kelp: 7,800 mcg per gram (5,200% of the RDI)

Note:While kelp is a rich source of iodine, it is important to consume it in moderation. Excessive intake of kelp may lead to iodine-induced hyperthyroidism (19), especially in individuals with existing thyroid conditions.

Apart from seaweed, many types of seafood and iodized salt have high iodine content.

Lack of iodine intake may lead to hypothyroidism (20), where the thyroid releases less hormones and eventually becomes underactive. Symptoms of hypothyroidism include fatigue, tingling sensation in the arms and legs, depression, dry skin, forgetfulness, and weight gain (21 22).

It’s recommended for an adult to take about 150 mcg of iodine daily (23). Including a couple of servings of seaweed a week may help reach the daily requirement easier. Always eat seaweed in moderation, especially seaweed like kombu and dulse as they contain extremely high levels of iodine. Other seaweed varieties like spirulina contain very low iodine, so eating it may not meet daily iodine requirements.

May Help Reduce Allergy Symptoms

Seaweed contains bioactive compounds called Fucoidans that can help with allergies. Brown seaweed is especially rich in Fucoidans. These compounds soothe the body’s response to allergens by reducing inflammation and stabilizing the cells that make allergic reactions (24).

Another compound called phlorotannin, found in some seaweed, has also shown similar allergy-reducing effects (25).

Research suggests that regularly consuming seaweed during pregnancy may help reduce allergy symptoms, like runny nose (26).

May Help Reduce Inflammation

Seaweed is rich in atioxidants that can help reduce inflammation in the body (27,28, 29, 30).

Fucoidans, in particular, are responsible for this anti-inflammatory effect of seaweed (31).

Seaweed is also rich in polyphenols, polysaccharides, and healthy fats (EPA and DHA). These compounds are known for their anti-inflammatory properties (32, 32).

Even though more research is needed to understand the seaweed’s anti-inflammtory effects, there is no denying that consuming it will promote overall well being.

Improves Digestive Health

Seaweeds play an important role in supporting digestive health and maintaining a healthy gut microbiome (33). Because of its high fiber content, seaweed keeps your digestion running smoothly and prevents constipation (34)

Seaweed also contains prebiotics such as carrageenans, agars, and fucoidans. These prebiotics act as food for the gut and promote good gut bacteria while swiping away the harmful ones (35). Getting rid of harmful bacteria helps reduce inflammation in the gut.

Over time, inflammation can cause issues such as stomach ulcers and inflammatory bowel disease (36). So, if you want to keep your gut happy and healthy, adding some seaweed to your diet might do the trick.

May Help Control Blood Sugar

Regular seaweed consumption may help reduce the risk of developing type 2 diabetes (37). Compounds in seaweed, such as fucoxanthin, have shown to play an important role in combating insulin resistance by stabilizing blood sugar levels (38).

Additionally, the fiber content found in seaweed may aid in blood sugar regulation by slowing the absorption of carbohydrates from meals (39). One study found that consuming brown seaweeds at the same time as meals improved blood sugar control and appetite regulation after eating in healthy adults

Although seaweed consumption has been shown to effectively control blood sugar levels, an accurate dosage for this purpose remains unknown. More research is required to further analyze the effects that has on blood sugar.

Potential for Lowering Cancer Risk

According to research, regular seaweed consumption may help lower estrogen levels, which may lower the risk of breast cancer (41, 42, 43). There are also certain compounds found in brown seaweed, like wakame, that may help by preventing the spread of cancerous cells (44).

However, it’s important to keep in mind that the relationship between seaweed and cancer risk is not yet fully understood by scientists. Even though seaweed holds numerous benefits, consuming too much of it may increase the risk of thyroid cancer (45).

Adding seaweed to your diet should be done in moderation and as part of a balanced diet. There is more research to be done in order to understand the impact that seaweed has on human health.

Tips for Eating Seaweed

Although seaweed is often overlooked, it’s an amazing ingredient to make your dishes more flavorful and nutritional.

Explore Your Local Stores

If you want to find out if seaweed is available in your area, check out your nearby grocery stores. Asian food markets usually keep many variations of seaweed in stock. You will most likely come across dry seaweed options like nori and dulse.

Get Creative in the Kitchen

There are endless ways to use seaweed in dishes. Here are a few tips that may inspire your next meal:

  • Toss a fresh seaweed salad by mixing wakame with scallions, vinegar, garlic, and sesame oil.
  • Simmer dried kombu or kelp to create a delicious flavorful soup broth.
  • Simply enjoy dry nori or dulse as a crispy treat.
  • Sprinkle a blend of kombu, nori, and dulse flakes on top of your rice dishes.
  • Enhance the flavor of beans by adding kombu while cooking them.
  • Try making a vegan tuna salad by combining dulse flakes, mayonnaise, chickpeas, red onion, celery, salt and pepper.
  • Make homemade sushi rolls using nori as sushi wrap.

Seaweed is highly nutritious and easy to add to your diet. By exploring different types of recipes and experimenting with various types of seaweed, you’ll discover new tastes and reap the health benefits that this ocean treasure has to offer.

Risks of Seaweed

Consuming seaweed is considered safe for most people. However, it’s important to cover some of seaweed’s potential risks:

  • Iodine overload: Although iodine is important for proper thyroid function, taking too much of it may lead to hypothyroidism. It’s recommended to consume less than 1,100 mcg of iodine in one day (46).
  • Heavy metal content: Some seaweeds contain high levels of heavy metals such as mercury, arsenic, lead, and cadmium. This depends mainly on location and cultivation methods (47).
  • Medication interference: Seaweed contains high amounts of potassium which may not be beneficial for those suffering from kidney disease and may interfere with blood thinning medications.

It’s important to be mindful of the risks associated with too much seaweed consumption. Consulting with a healthcare provider or certified dietician is the best way you can make informed choices and enjoy the health benefits that seaweed has to offer while avoiding its harmful risks.

Frequently Asked Questions

Can you eat Seaweed raw?

Yes, you can eat many types of edible seaweed raw. In fact, it’s commonly eaten this way in some cultures, particularly in salads or sushi. However, some varieties of seaweed can taste tough and chewy if eaten raw, and is better cooked.

Can Seaweed cause diarrhea or constipation?

Although Seaweed helps promote gut health, eating large amounts of it may cause diarrhea in some people. This is mainly because of its high fiber content and the presence of certain sugars that the body may have difficulty digesting. Eating large amounts may also cause constipation if someone consumes it in large amount without proper hydration.


Consuming seaweed has been linked with many health benefits, such as supporting thyroid function, improving heart health, and boosting the immune system. Seaweed is nutritious, low in calories and comes in different varieties and tastes. It can be added as an ingredient in various dishes.