Edible seaweed benefits your whole body

Seaweed Types, Health Benefits and Recipe Ideas

Published: March 2021 | Updated: April 2024

By: Holli Ryan, RD, LD/N

Working on eating more vegetables daily? I bet that sea vegetables aren't the first thing to come to mind. However, those almost alien-looking plants that grow in the ocean can, in fact, be a valuable part of your diet, not to mention delicious in recipes!

Sea vegetables are a type of algae (a large group of aquatic plants) that grow in the ocean. Edible seaweed falls into three categories: red algae, brown algae and green algae. This low-calorie and nutrient-dense food has long been harvested and consumed in Asian cuisine, particularly in Japan and Korea, where dishes like wakame and hijiki (and of course sushi) are popular.

In fact, experts have suggested that regular intake of edible seaweeds is one of the factors that contributes to the long lifespan enjoyed by residents of Okinawa, Japan as a staple of the Japanese diet. Japan has a high amount of centenarians per capita, and the Japanese diet is thought to contribute to this.

So let's dive in to the world of seaweed and explore the benefits!

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Nutrition facts about edible seaweed

Let's start with the nutrients. Here is a quick overview of some key nutrients found in edible seaweed.

  • Iodine and other minerals
  • Fiber
  • Polyphenols
  • Protein
  • Omega-3 fatty acids EPA and DHA
  • Vitamin K and other vitamins
  • Poly- and oligosaccharides that function as prebiotics
  • Beta-glucans

Edible seaweed is a great addition to almost any diet, and it can help provide vegetarians and vegans with certain nutrients they may be lacking, such as vitamin B12, amino acids, DHA, and iodine.

Pro tip: seaweeds absorb nutritive and non-nutritive minerals from their environment. Be sure to choose a quality product that ensures it has been tested for environmental contaminants such as heavy metals. Additionally, watch out for the sodium content, especially if following a low-sodium diet.

Health benefits of sea vegetables

  • Immune system support
  • Thyroid health
  • Gut health
  • Healthy blood sugar support
  • Brain health
  • Cardiovascular health
  • Healthy aging

It turns out that those plants from the ocean are an excellent source of iodine, an essential mineral for thyroid health. Additionally, a meta-analysis of 25 clinical trials using various seaweeds (as supplements or dietary additions) found that consumption of these plants was associated with a variety of benefits, including cardiovascular, thyroid, blood glucose metabolism, and antioxidant benefits. A study surveying nearly 100,000 Japanese people aged 40-69 found that consumption of sea vegetables was associated with heart health. The omega-3 fatty acid DHA derived from sea vegetables is a great option for vegans and vegetarians who do not eat fish or take fish oil, which is important to maintain heart health and more. Plus, the prebiotic fibers found in seaweeds may also benefit gut health.

What are the different types of seaweed?

Fun fact: the number of species of algae in the ocean is estimated to range from 30,000 to more than 1 million! AlgaeBase, an online database, lists 175,063 species. But to make this vast array a little easier to navigate, edible seaweed are classified into three groups based on their colors: brown algae, green algae, and red algae.

1. Brown seaweeds

Brown sea vegetables contain fucoidan, a type of carbohydrate found in wakame and other plants this color. Fucoxanthin is a carotenoid found in brown sea vegetables.

Kombu (Saccharina japonica)

Kombu is widely consumed in Asian countries and the fermented variety have intrigued researchers as the benefits may be further enhanced after fermentation. Kombu, not to be confused with kombucha, is an integral ingredient for making dashi, a clear but flavorful stock that is the cornerstone of Japanese cuisine and serves as the base for miso soup.

Sugar kelp (Saccharina latissima)

Closely related to Saccharina japonica, sugar kelp contains mannitol, a naturally occurring sugar that will add sweetness.

Kelp (Ascophyllum nodosum)

This variety grows on the coast and is typically found as a powder or supplement form as a source of iodine.

Bladder wrack (Fucus vesiculosus)

Bladder wrack is similar to kelp, which grows in coastal areas, and is also available as a supplemental source of iodine.

Patagonian wakame (Undaria pinnatifida)

As a source of fucoidan, wakame has been primarily studied for its benefits to immune function. If you are interested in adding it to your regimen but don't dine regularly on wakame, Maritech® 926 is a fucoidan extract sourced from hand-harvested, wild sea plants growing in the pristine ocean waters of Patagonia. A single vegetarian capsule of Optimized Fucoidan with Maritech® 926 provides 88.5 mg of standardized Undaria pinnatifida extract, equaling the amount of fucoidan typically consumed daily in the traditional Japanese diet.

Hijiki (Sargassum fusiforme)

Hijiki grows along the rocky coastlines of Japan, Korea and China and is said to have a strong, salty flavor. Hijiki turns black after being boiled and dried and takes on a thin strand-like appearance once it's reconstituted and prepared for eating. Like other types of seaweed, hijiki is a source of dietary fiber and minerals. However, more human studies are needed to confirm variety-specific benefits.

2. Red seaweeds

Red sea vegetables (Rhodophyta) are composed of about 7,000 species.

Nori (Porphyra yezoensis)

Despite its dark green or even black appearance, this common edible seaweed is prevalent even here in the U.S. If you enjoy sushi rolls regularly, you are also enjoying the benefits of nori which comprises the "wrap" portion of the roll. Nori is a source of protein, antioxidants, vitamin B12, and other nutrients.

Dulse (Palmaria palmata)

Found along the rocky northern coasts of the Atlantic and Pacific Oceans, dulse can be eaten fresh or dried. Dulse is enjoyed in traditional Irish and Icelandic dishes, and is commonly served with fish and butter. In a randomized double-blind placebo-controlled trial, 2 grams of dulse a day was found to help support healthy triglyceride levels.

Sea moss (Chondrus crispus)

Also referred to as Irish moss, this type of sea moss has gained quite the buzz in recent years. You may have seen it at your local farmers market or used in vegetarian-friendly foods as a replacement for gelatin. Carrageenan, a gel-like substance found in its cell walls, is used as a thickener and stabilizer for foods and beverages such as dairy milk alternatives. Aside from its culinary and food industry uses, does it live up to the hype for our health? Like other seaweeds, it is a source of minerals, omega-3, and prebiotic fiber. These nutrients can support thyroid, gut health, bone health, and more.

Ogonori (Gracilaria)

Ogonori is sometimes pickled or used in salads and is a popular ingredient in the Caribbean and in Hawaii where it might be found a bowl of poke. Similar to Irish moss, ogonori is a source of agar-agar, a jelly-like substance that is a vegetarian counterpart for gelatin. It can be used to make jellies, puddings and custards.

3. Green seaweeds

Edible seaweed that is green in color (Chlorophyta) gets its pigment from chlorophyll.

Chlorella (Chlorella sp.)

Chlorella is a green unicellular microalgae, in contrast to the macroalgae species discussed above. Small but mighty, it is a source of a variety of nutrients such as vitamins and minerals. A meta-analysis on the effects of chlorella supplementation found that it can support heart and liver health.

Spirulina

Spirulina is sometimes referred to as blue-green algae but is actually a bacteria that is "algae-like." Spirulina is a source of protein, B12, iron, beta-carotene, and fatty acid GLA. Some research indicates it may help our response to seasonal changes.

Sea grapes or green caviar (Caulerpa lentillifera/Caulerpa racemosa), "Umibudo"

Popular in the Philippines, Malaysia, and Japan, sea grapes are one of the few varieties sold fresh. Like caviar, the tiny pearls burst in the mouth when eaten and release the brininess of the sea. Although sea grapes contain polysaccharides which can act as prebiotics and dietary fiber, minerals, and vitamins, more human studies are needed to confirm variety-specific benefits. Interestingly, C. lentillifera is considered to be a source of high-quality protein as the essential amino acids present make it similar to egg and soy in terms of protein content.

Sea lettuce (Lumot/Rupurupu/Limu ele-ele/Limu pipilani) Ulva spp.

As the name indicates, sea lettuce has leaf-like structures that resemble garden lettuce. It can be eaten raw or cooked and is high in fiber, minerals like iron, and vitamins. But unlike land lettuce, it is approximately 13.6% protein by dry weight.

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Seaweed recipe ideas

So how can you eat sea vegetables? Turns out, there's plenty of ways: with rice dishes or incorporated into miso soup or as seaweed salad. The major amino acids in its proteins are aspartic and glutamic acid, which contribute to the umami flavor, making it a great addition to savory recipes.

Some of the most commonly eaten varieties include: nori, kombu, wakame, and sea moss, with nori being the most popular in the U.S. You may be surprised to find (as I was with mine) that your toddler loves to snack on crispy sheets of roasted nori, which are widely available at many commercial grocery stores. Other varieties that you won't find there may be available in specialty stores and Asian food markets.

Here are some fun and easy recipes.

Poke bowls or noodle bowls

This treasure from the sea makes a great topping to add additional favor, color, texture, and of course nutrition to your favorite poke or noodle bowls.

Seaweed salad

Seaweed salad is commonly served as a side dish in Japanese cuisine. It's simple to make at home using sea vegetables of your choice along with a soy sauce and vinegar-based dressing.

Sushi burrito

This trendy food is not only Instagram-able but can do double-duty by delivering a healthy dose of fillings: vegetables, protein, you name it. Like its roll counterpart, sushi burritos usually use nori. They are like your favorite roll, but just are not sliced.

Temaki handrolls

If you're not sure about the intricate work that goes into making, say, a maki roll, a handroll is an easy alternative! Plus, if you are cutting back on starches such as rice, this is a good option that omits it.

Whether seaweeds already are a staple in your kitchen or you're just ready to expand your recipe repertoire and get adventurous and benefit from sea vegetables, there are many ways to enjoy these nutrient-dense treasures!

About the Author: Holli Ryan is a food & nutrition expert, registered & licensed dietitian-nutritionist, health & wellness writer, blogger, and social media specialist. She graduated from Florida International University and is a member of the Academy of Nutrition and Dietetics. In her free time she enjoys photography, travel, cooking, art, music, and nature.

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