Forget that image of a creature from the sea, dripping with seaweed, lurching toward bikini-clad beach-goers. Considering the enormous health benefits of these phytonutrient-rich greens, we might instead wonder why Popeye didn’t opt for them over canned spinach. Maybe it’s in the name. “Seaweed” is a blanket term that’s been attached to a vast group of sea vegetables, some varieties of which are invasive algae, hence the suffix “weed.” Its benefits aren’t limited to nutrients, either – seaweed can be farmed sustainably on coasts around the world, improving the environment as it grows.
A staple of East Asian cuisines, seaweed is slowly making headway in American food culture, mostly thanks to Japanese restaurants. Although 99 percent of the world’s production of seaweed is consumed in Asia, Western European cultures have a history of eating seaweed, too. And we may see more of that in the future, as troubled fishing industries in North America turn to seaweed and sea vegetable aquaculture as a viable alternative.
But first, what exactly is seaweed? What types exist, and how are they eaten? Given its vague definition, there are thousands—if not millions—of distinct weeds from the sea. Here are some of the most common varieties used for human food, along with brief descriptions and culinary uses.
Kelp: A group of seaweed species with large, broad leaves that may be brown or dark green. Varieties include kombu which are thick, dried sheets used to flavor stocks, and wakame, often served in cold salads or soups, in Japanese cuisine.
Laver: Typically thick and tough, this group of seaweeds ranges from reddish-brown or purple to bright lime green (the latter is called “sea lettuce”). Easily found in the wild, they are eaten in a traditional Welsh dish called laverbread; and in Japan, this type of seaweed is dried and roasted until crackly as nori, often found in sushi.
Hijiki: These dark-brown algae that resemble crinkly threads are a specialty in Japan, where they are often marinated and eaten in cold salads.
Dilisk / Dulse: This large, brown seaweed grows in leathery-textured clumps and has a long history of being enjoyed in Iceland and Ireland. It’s often eaten simply sundried, as a snack.
Sea Beans / Sea Asparagus: These green, finger-shaped succulent plants are known botanically as salicornia and can be found on haute restaurant menus in the US nowadays. With a mild taste, they are usually prepared minimally by boiling or steaming and sprinkling into salads.
A Brief History
The consumption of seaweed in various coastal areas around the world dates back thousands of years. There is evidence that seaweed was eaten and used for medicine in Chile 14,000 years ago. It has also been a traditional food of the Maori peoples of New Zealand.
The earliest known record of eating seaweed in the Western World dates to around 500 BC, in a Scottish poem describing the monks of Iona who ate porridge and seaweed as a paltry diet. In the Western world, eating seaweed was hence associated with being poor and desperate for nutrients, given the scarcity of vegetables throughout the cold months. Yet it has been enjoyed throughout the centuries, with some notable traditions such as laverbread, in coastal regions of Iceland, Ireland, Scotland, Norway and Great Britain.
In Asia, seaweed has been incorporated into everyday diets since prehistoric times. Since seaweed is easily dried to lightweight, shelf-stable products, the enjoyment of seaweed was also not limited to coastal areas as was common in the West. Depending on the variety and processing methods used, seaweeds are even regarded as delicacies. High-grade kombu, for example, is especially sought after in Japan as a flavoring agent in soups. In Japan, China and Korea, numerous forms and shapes of seaweed are eaten as additions to soup, or as chilled salads, in the average household.
- During the 18th Century, kelp ash was a hot commodity in Britain, where it was used in glassmaking. It was a cheaper, domestic source of sodium bicarbonate than imported Spanish barilla, also used to make “soda ash.”
- The seaweed variety known as hai zao has been traditionally used in Chinese medicine to treat thyroid disease.
- The word “laver” is derived from an Old English name of a sea vegetable written about by Pliny the Elder—not to be confused with the French word laver, from Latin for bathing, or place to bathe.
- You can laver in laver, however: in Ireland, spas specializing in vitamin-rich seaweed baths were found throughout the country around the turn of the 20th century. Some still exist.
Like fish, seaweed was traditionally foraged wild from the sea. Seaweed farming as a more reliable means for producing quality seaweed was first developed in Japan in the 1600’s. Early methods of seaweed farming involved placing bamboo sticks in shallow waters, where spores would attach to the wood naturally and grow along its length (a process quite similar to oyster farming). Today, large nets or ropes of synthetic material are more commonly used, making harvesting more efficient.
For as long as Asia has been farming seaweed, North America is just getting started. Because of its beneficial effects on the environment and its relatively easy, low-tech operations, kelp farming has been making headway in the Northeast in recent years, as well as in Mexico, where recent efforts have been helped in part by the marine conservation organization Olazul.
Seaweed grows well in winter, and commercial seaweed farming often begins in the fall, and the mature plants are harvested in the spring. This ensures a cleaner product; it’s harvested before biofouling and competing algae can begin to deteriorate its quality. After harvest, the seaweed is commonly sundried until brittle. There is hardly an expiration date for this food afterward; lightweight and easy to store, dried seaweed is available year-round in markets.
Seaweed farming is praised for its beneficial effects on the environment. Seaweed naturally removes nitrogen and other contaminants from the water. Seaweed meal made from brown seaweeds, which have absorbed more nitrogen, are often used as a fertilizer for soil on land farms. It provides land plants with a rich meal of vitamins and minerals that encourages growth. Seaweed fertilizer has also been found to improve soil by stimulating bacteria activity and helping retain water.
While controlled seaweed farming operations are low-cost and actually a boon to its environment, wild seaweed washed ashore caused a health scare in 2009. In Normandy, excessive amounts of green seaweed rotting on the beach created toxic fumes that were dangerous enough to kill several wild animals. The excess of seaweed was linked to increased industrial agriculture in the area, with nitrate runoff encouraging the growth of green seaweed.
It’s worth noting that the biggest advantage of seaweed from an environmental perspective is that it requires no fertilizer or fresh water to grow. When you compare that with other vegetables like, say, spinach or kale, which require intensive amounts of (non-salty) water along with fertile soil and sun for cultivation, seaweed looks effortless. And after all that, these land plants are only fresh for a few weeks unless frozen (which requires much energy).
Characteristics and What to Look For
Look for seaweed in the international foods aisle of a big supermarket, or in an Asian grocery. You’ll find it dried in bags, appearing like dark, crinkled sheets (as for popular edible varieties wakame and kombu), or as thin, crisp sheets (as for nori). Don’t mind the whitish cast that may be visible on the surface of dried seaweed; if it’s fully dried, that’s salt remnants, not mold. There are more seaweed and seaweed-flavored snacks on the market today than ever, boasting the health benefits of seaweed even in crispy, fried forms. Bite-size sheets of roasted nori, sprinkled with salt, have become a popular obsession in health food stores. In a well-stocked Asian market you may be able to find fresh, or fully reconstituted, seaweed in the refrigerated produce aisle—like ribbons of kelp that are tied into knots, for example. Seaweed can be found sold frozen from a few domestic sources, such as Ocean Approved, too.
A few tips for foraging seaweed from the wild have surfaced, although harvesting wild seaweed is not regulated and therefore not recommended in general. If dabbling, however, it’s best to soak and drain the collected seaweed a few times to rinse impurities.
Seaweed is a superfood that offers many benefits when consumed. As its appearance hints, leafy green seaweed is incredibly dense in vitamins, like Vitamin K, Vitamin A and antioxidants. Its mineral composition is even more impressive; it provides a high amount of calcium, protein and soluble fiber. It’s also packed with iodine, an essential nutrient that’s often added to table salt, and promotes thyroid and brain functions.
Eating seaweed also helps alkalize the body and is therefore an important part of a modern diet. With so many foods that are acid-forming, eating more alkaline foods helps your body balance its pH level. Seaweed is a highly detoxifying food, protecting our bodies against environmental and other toxins. However, some have become wary of seaweed’s ability to absorb toxins and other contaminants from the sea, carrying them into your body at the same time. Scares of contamination in seaweed have occurred in areas with industrial runoff and chemical waste—including radiation pollution in seaweed after the Fukushima nuclear disaster. However, credible seaweed producers ensure safety and quality through testing. In fact, studies suggested that eating seaweed as part of a healthy diet helped reduce the effects of radiation poisoning in patients after the bombing of Hiroshima.
What to Do with It and Cooking
With all the health benefits of seaweed, it’s no surprise that supplements are readily available in health food stores. But that would be denying how delicious and versatile these edible weeds can be. Seaweed is one of few plant-based sources of umami, a flavor profile that’s best translated as “savory” in English. Its generous flavor can be absorbed into soups, like the classic dashi broth or miso soup, and hidden from view. Or it can be eaten whole, fresh or dried.
An easy way to start eating seaweed is to fully soak a leafy green variety, such as wakame, and toss it in a sesame-based vinaigrette, or just a drizzle of sesame oil and rice vinegar. Chefs have been experimenting with seaweed in playful preparations like seaweed pesto. You can crush dried seaweed into a powder to sprinkle atop foods as a seasoning (found also in various mixes called furikake in Japanese cuisine). You can fold that powder into a savory baked good, as a nod to laverbread. Or make a hand roll with sticky sushi rice and any toppings rolled into a cone of nori. Works as a snack on the go!
Spicy Asparagus or Okra Rolls
(from Not Eating Out in New York)
(makes 3 rolls, or 15-18 pieces)
3 square sheets of nori seaweed (can be found in packages at most Asian groceries)
1 cup uncooked sushi rice
4 tablespoons sushi vinegar*
about 1 lb fresh asparagus, okra or a mixture of both
1⁄4 cup mayonnaise
2 teaspoons chili sauce, such as Sriracha
toasted sesame seeds (optional)
*I used a bottle of stuff simply called “Sushi Vinegar,” and its ingredients are vinegar, water, sugar and “seasonings.” If you want to mix up your own from scratch, get yourself some Japanese rice vinegar and dissolve sugar and salt into it, following one of these recipes.
- Rinse and drain the rice, and cook in a rice steamer according to your machine’s regular instructions. In the meantime, spread about half of the sushi vinegar into the bottom of a large square or rectangular baking pan (unless you have the traditional porous, wooden flat-bottomed bowl, or hangiri, which is preferred). Transfer the rice to the pan and gently mix with a soft rubber spatula, while you fold in the rest of the sushi vinegar. Do not overmix, as you don’t want to break any of the grains. Cover the pan with a wet towel and let cool to room temperature before using.
- Meanwhile, preheat oven to 450 degrees. Snap off any tough ends of the asparagus and arrange flat on a cookie sheet or roasting pan along with the whole, washed okra pods, if using. Roast for 3-4 minutes, then stir up the vegetables with a pair of tongs. Roast another 2-3 minutes. Remove from heat and let cool.
- Place a square of nori on top of a sushi rolling mat (these are ideal because its long slats of wood distribute pressure throughout the length of the roll). Wet your fingertips, and place little handfuls of rice evenly on top of the nori square. Spread until it has reasonably even, light layer of rice.
- For asparagus rolls: depending on how thick your asparagus are, arrange a few stalks about a half-inch away from one end of the nori sheet, on top of the rice.
- For okra rolls: Cut off the stems of the okra pods once they have cooled. Arrange thick pods lengthwise a half-inch from one end of the sheet. Overlap a little when you come to skinny, pointy ends so that ideally, every piece of the roll will show a fat cut-out of okra.
- Dab one third of the spicy mayonnaise mixture along the length of the veggie filling. Lift up the straw mat on that same side, and roll until the nori covers the vegetables. Without pressing too hard, continue to roll, lifting the straw mat out of the way as you go along, until the entire nori sheet is rolled up. Press down a little bit on the finished roll to secure the ends (the sticky rice should help the roll stick together). Using a very sharp knife, cut the roll into five or six pieces. Place the pieces cut-side-up or down on a plate. Serve with wasabi and soy sauce.
Soba Seaweed Salad
(from The Candida Diet)
2 oz. soba noodles
1⁄4 cup dry Wakame seaweed
2 Tbsp. sesame oil
Sprinkle of sesame seeds
Salt to taste
- Soak the seaweed in a bowl with warm water for about 10 minutes.
- Boil the soba noodles for 6 minutes.
- Chop the tomatoes and avocado, then add everything to a bowl and mix.
- Drizzle with sesame oil and sprinkle with the sesame seeds
Seaweed & Tofu Soup
(from Eating Well)
1⁄4 cup crumbled dried seaweed, such as wakame or kelp (see Tip)
1⁄4 cup diced strip steak (optional)
1⁄4 cup thinly sliced scallions
2 teaspoons minced garlic
2 teaspoons toasted sesame oil
1⁄4 teaspoon freshly ground pepper
4 cups water
2 tablespoons white miso (see Note), or to taste
1⁄2 cup diced firm tofu
- Place seaweed in a medium bowl, cover with water and let soak for 20 minutes.
- Combine steak (if using), scallions, garlic, sesame oil and pepper in another bowl.
- Warm a medium saucepan over high heat and add the scallion mixture. Cook, stirring, until fragrant, about 1 minute. Stir in 4 cups water and miso. Reduce the heat to medium-low so the liquid does not boil. Whisk to dissolve the miso.
- Drain the seaweed and stir it into the soup along with tofu. Cook over medium-low for about 10 minutes. Remove from the heat. Taste and season with more miso, if desired.
Note: Miso is fermented bean paste made from barley, rice or soybeans used to add flavor to dishes such as soups, sauces and salad dressings. It is available in different colors, depending on the type of grain or bean and how long it’s been fermented. In general, the lighter the color, the more mild the flavor. It will keep, in the refrigerator, for at least a year.