Real Food Encyclopedia | Seaweed

Considering the enormous health benefits of phytonutrient-rich seaweed, it’s a wonder Popeye didn’t opt for it over canned spinach. “Seaweed” is a blanket term that’s been attached to a vast group of sea vegetables. Its benefits aren’t limited to nutrients, either — seaweed can be farmed sustainably on coasts around the world, improving the environment as it grows.

<<View All Real Food Encyclopedia Entries

Fun Facts about Seaweed:

  • 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 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.

What to Look for When Buying Seaweed

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 sun-dried, 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.

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.

Sustainability of Seaweed

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).

Seaweed Seasonality and Geography

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 sun-dried 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 and Cultivation

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 1600s. 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.

How to Cook Seaweed

Cooking With Seaweed

It’s impossible to deny 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!

Seaweed Nutrition

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.

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.