Sample a Sea Vegetable


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Imagine my surprise when, one night, some friends came to supper and brought dessert—made from seaweed! The gelatin-like confection was made of agar and coconut milk. We found it mildly sweet and surprisingly pleasant. Most people assume all edible seaweeds taste fishy, but they are more complex than that, with flavors ranging from very salty (and, yes, fishy) to delicate or bland.

Seaweeds can be used in desserts, salads, soups, stir-fries, pasta fare and bean dishes, and some even can be eaten as snacks. They are rich in nutrients and contain bioactive compounds that may thwart cancer, fortify the immune system and support the thyroid. So if you’ve bashfully avoided these jewels of the sea, here are a few worth meeting.

Choose Your Type

Seaweeds are large algae (or macroalgae) that live in the oceans, seas and brackish waters. There are three main types: red, brown and green. Not all seaweeds are safe to eat, but the edible species that serve as sea vegetables can bring a rounded, salty flavor to food, adding variety and important nutrients to our diets.

Relish the Reds

Agar (Gelidium spp.). Known also as agar-agar (a Malay term) or Japanese gelatin, this mild-tasting sea vegetable is translucent and almost colorless when you buy the dried strands. (It typically is dried in the sun, which bleaches out the color.) Agar often is used as a natural gelling agent or thickener in jellied desserts, aspics, molds, pies and puddings. Whole dried agar is either boiled to release the gelling agent for thickening, or soaked and chopped into salads, soups and other dishes. You also can sprinkle dried agar flakes onto fruit juice, soup stock or other liquid, simmer a few minutes to dissolve, then cool to thicken or solidify.

Nori (Porphyra spp.). The favorite of sushi lovers, purple-hued nori turns to phosphorescent green when dried and toasted. Nori sheets can be used to fashion sushi rolls or crumbled into soups and chowders. Nori also is sold as powder or flakes that can be sprinkled as a slightly salty seasoning onto grains, mild-flavored vegetables, seafood, tofu or pasta.

Irish moss (Chondrus crispus). A main ingredient in the classic pudding-like dessert known as blancmange, Irish moss has long been a popular food. It is widely used as a source of carrageenan—a natural gelling agent used to thicken and stabilize soups, dairy products, and a host of commercial confectionary products and pharmaceuticals. Irish moss contains more than 60 percent carrageenan. It is available in dried form.

Dulse (Palmaria palmata). Often eaten as a healthy snack right out of the bag, dulse has a salty flavor yet is relatively low in sodium, compared with other sea vegetables. Its tangy marine flavor works well in salad dressings, soups and sautés. Some people eat it fresh by grabbing a handful off the coastal rocks to which dulse attaches itself. If that’s too adventurous for you, try it baked, fried or simply sun-dried. It comes as whole fronds as well as flakes or powder.

Brown Sea Vegetables for Real Marine Character

Brown sea vegetables can have a distinct marine, or “fishy,” flavor, so they should be used with a light hand. Some types are mild and are ideal for newcomers to sea vegetable cuisine.

Kelp (Laminaria spp.). Kelp’s ribbon-like fronds have a strong flavor. Kelp can be eaten whole or chopped, but is best known in North America as a dietary supplement and for its MSG-like tenderizing action on meats. Uncooked, kelp tends to be salty and acrid, but frying or toasting tones down the marine taste a bit for sautés, stir-fries and soups. Kelp is excellent as seasoning flakes instead of salt. An Asian type known as kombu (L. japonica) frequently is added to cooking liquid for rice, beans and soups to enhance their flavor. A stamp-sized piece of dried kombu cooked with beans will help make them more digestible.

Milder-tasting members of the kelp family include ocean ribbons (Lessoniopsis littoralis), which cooks quickly for Asian stews and tamari dishes; wakame (Undaria pinnatifida); and alaria (Alaria spp.). All are great choices for the first-timer. Wakame and alaria are good in miso soup, or tossed with orange slices and chopped scallions into a salad. First-timers also might enjoy arame (Eisenia bicyclis), whose thin black strands can be simmered with tamari, lemon juice and rice wine, then sprinkled with toasted sesame seeds; or sea palm (Eisenia arborea), whose fronds are delicious raw or added toasted to trail mix, granola, quiches or omelets.

Bladderwrack (Fucus vesiculosus). A common food in Japan, bladderwrack also is used as an additive and flavoring in many European food products. In North America, it typically is used in kelp nutritional supplements and teas, although “kelp” technically refers to a different seaweed species. You’ll see bladderwrack in some oral over-the-counter products for heartburn—its alginic acid (in this and some other seaweeds) swells upon contact with water and helps seal the top of the stomach during digestion. The same constituent also functions as a laxative.

Sea Lettuce: A Novel Take on Salad

Bright green sea lettuce (Ulva lactuca) grows in thin, frilly sheets that really do resemble terrestrial lettuce. It adds flavor and color to many dishes, and can be used raw in salads, toasted and crumbled into soups and sauces, or even as an ingredient in ice cream. Sea lettuce can be stored in the fridge for two to three weeks or frozen for up to six months without losing its flavor.

Despite its positive culinary attributes, however, you won’t find many fans of sea lettuce among water resource managers. Although under natural conditions sea lettuce plays an important role in the ecosystem for small fish and birds, today it tends to multiply quickly in polluted areas and can stifle other aquatic plants. So check the origin of your product before purchase—it should provide assurance that it comes from a non-polluted environment, preferably by making results available from analyses of chemical residues.

Nutrient Supply

Sea vegetables—especially kelps—are excellent sources of macrominerals, trace elements and some vitamins, with notably high levels of iodine, magnesium, vitamin K and folate. They are rich sources of dietary fiber, essential amino acids and essential omega-3 fatty acids, particularly eicosapentaenoic acid, which can be as high as 50 percent of total fatty acid content. (In fact, fish get their omega-3s from eating seaweeds, since they don’t make their own.) A recent report in Food Chemistry indicates that various types of seaweed were found to contain a nutritionally ideal balance of omega-6 to omega-3 fatty acids.
Seaweeds—typically kelps in whole or supplement forms—traditionally have been promoted for treating hypothyroidism. However, caution is needed because, while they can help if there is an iodine deficiency, taking excessive iodine when you don’t need it might disturb normal thyroid function. The U.S. Food and Drug Administration recommends 150 micrograms of iodine daily for adults, which is present in about 4 teaspoons of kelp.

Brown Seaweed—Cancer’s Foe?

For centuries, certain sea vegetables have been used in Japanese and Chinese medicine for the treatment of cancer.  Several laboratory studies have stoked interest in seaweed’s anti-cancer possibilities, but results from human clinical trials are not yet available. 

Fucoidans, which are complex polysaccharides found in the cell walls of many brown seaweeds, have anti-cancer actions. For example, they can prevent tumor cells from latching onto other parts of the body, thereby stalling metastasis. And they boost the activity of natural killer cells which destroy tumor cells.
Fucoidans might hinder other invaders, too, such as viruses. Lab research with kelp points to antiviral action against influenza, herpes simplex and HIV. Fucoidans can induce viral cells to self-destruct, as shown with the virus that causes human adult T-cell leukemia.

Another polysaccharide, carrageenan—prevalent in red seaweeds such as Irish moss—has been shown in lab tests to fight the human papillomavirus (HPV), which is linked to cervical cancer. Carrageenan is used as a thickening agent in many everyday foods (e.g., coffee creamer, yogurt, chocolate milk and desserts), but whether the small quantities used are sufficient to provide anticancer benefits is not known.

Seaweeds Bind Heavy Metals

Seaweeds have long been known to bind dangerous heavy metals in the body that contribute to cancer and a host of other problems. Alginates, for instance, which are polysaccharides found in brown seaweeds, can bind and reduce the amount of the radioactive element strontium-90 absorbed by the human body.

The flip side is that seaweeds also can concentrate heavy metals and other contaminants from the sea and expose them to your body. Reliable seaweed suppliers (such as Maine Coast Sea Vegetables in Franklin, Maine; test for residues of heavy metals, pesticides, herbicides, PCBs and other contaminants, and make their results available to buyers.

Ensure Best Quality

You can buy sea vegetables in health-food stores, fish markets, Asian markets, specialty sections of your local grocers and on the Internet. Look for tightly sealed packages with no excessive moisture, and store items tightly sealed at room temperature. Dried sea vegetables will keep for several months.

“Organic” products are available, but since it is impossible to fully control the growing environment of wild sea vegetables, organic certification governs mainly harvesting and handling practices and quality testing (e.g., for chemical residues). Look for certification from a recognized body such as the internationally based Organic Crop Improvement Association.

Overall, sea vegetables can be an exciting addition to your cookery. But buy from a reputable supplier, read quality test results, and consume only small servings (typically less than 1/4 cup). Remember—a little seaweed goes a long way!

Gina Mohammed, Ph.D., is a plant physiologist in Sault Ste. Marie, Ontario, Canada. She is the author of Catnip and Kerosene Grass: What Plants Teach Us About Life (

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