If ever a seafood deserved the name super, it’s seaweed! There’s no end to the ways seaweed is used. It can be eaten fresh, dried, frozen, cooked, used in baked goods, added to soups, rolled into sushi, and more. You also likely have seaweed in your home already without even realizing it. Extracts from seaweed are used as additives in foods and other consumer products — even beer! Giant kelp, for example, is a source of algin, an emulsifying and binding agent used in the production of many foods and cosmetics like ice cream, cereal, and toothpaste. (The Monterey Bay Aquarium logo also represents the tip of a growing giant kelp!)

The name seaweed is a little deceptive. They’re not plants at all. Seaweeds are a large, diverse group of marine macroalgae that can be subdivided into three distinct groups: brown, green, and red algae. Seaweeds don’t have roots, stems, or leaves like plants; instead, they have holdfasts, stipes, and fronds. While they might look similar, these features have different functions and structures. Holdfasts anchor seaweed to the seafloor, stipes are similar to stems, and fronds look a lot like leaves.

Seaweeds generally grow in coastal waters where they can anchor themselves to the seafloor but still get enough light for photosynthesis. Like plants, seaweeds use photosynthesis to create their own energy! Seaweed is an important component of ocean ecosystems. They provide oxygen, food, and habitat for fish and other marine species.

Thanks to its rich umami flavor, diverse applications, and nutrient-density, seaweed has been an essential part of traditional diets in many coastal communities over the centuries. In Japan, Korea, and China, a variety of seaweeds are enjoyed in salads, soups, and side dishes. In Scotland, Irish moss is used in puddings, and, in some Indigenous cultures in the Americas, kombu seaweed is simmered with beans.

The vast world of seaweed offers a delicious array of options, much like your other favorite leafy greens. While there are more than 10,000 types of seaweed, some varieties commonly available in the U.S. include hijiki, kombu, and nori. Each type of seaweed has its own unique attributes, with flavors that range from rich and savory to mildly sweet and nutty; deep colors like red, green, brown, and black; and textures such as smooth fronds, small twigs, and wide strips. 

Seaweed farmed using off-bottom aquaculture is one of the most sustainable seafood items you can buy. Seaweed sequesters carbon, provides important marine habitat, and helps support biodiversity.

Seaweed is one of the world’s most nutrient-dense foods. While each variety has its own unique nutritional profile, its general nutritional benefits include:

• Being a health powerhouse. Seaweed contains a variety of 23 essential nutrients, including vitamin A, iron, and magnesium.
• An excellent source of iodine, a mineral which supports thyroid function and a healthy metabolism.
• Bioactive compounds, such as astaxanthin, porphyran, and fucoidan, which have been researched for their potential health benefits including cancer-fighting, antioxidant, and anti-viral properties.
• Beneficial prebiotics, which promote a healthy gut microbiome and help boost immune health.
• Promoting heart health. Seaweed's natural profile of low to moderate sodium and high glutamic acid (an ideal salt substitute) levels help keep dietary sodium intake in a healthy range.

Different types of seaweed provide different benefits. (Note: Seaweed omega-3 levels vary by species. See our FAQs at the bottom of the page for more information.)

• A kelp native to Japan, kombu has an astonishing 9333 percent Daily Value of iodine, 13 percent Daily Value of magnesium, and 14 percent Daily Value of potassium per serving (7 grams dried seaweed).
• A 7 gram serving of dried nori provides 98 percent Daily Value of iodine, 23 percent Daily Value of vitamin A, and 33 percent Daily Value of folate. This dried seaweed is often used to wrap sushi rolls.
• A brown kelp, wakame has 75 percent Daily Value of iodine and 24 percent Daily Value of magnesium per 7-gram serving (dried).

In 2018, there were over 32 million metric tons of seaweed produced globally. About 99.5 percent of that is farmed in Asia, with over half coming from China. There are about 10 different major species of seaweed farmed for commercial use, but kombu (Japanese kelp) makes up about 35 percent of this global production.

Seaweed farmed using off-bottom culture is rated green for environmental sustainability and accounts for almost 90 percent of the seaweed farmed worldwide. Off-bottom aquaculture methods grow shellfish, seaweed, and more in ways that don’t harm the seafloor. The vast majority of seaweed is grown using floating rafts with netting or longlines attached to them or lines that are staked to the ocean floor.

Overall, off-bottom culture methods have relatively few environmental impacts. For example, since these algae use sunlight and photosynthesis to nourish themselves, there’s no additional feed needed or nutrient waste discharged into the environment. Seaweeds also scoop up and store carbon dioxide and nutrients from the seawater around them.

Learn more about seaweed from Barnacle Foods

Explore other items on the Super Green List