When we talk about seafood, we usually mean fish and shellfish. But they aren’t the only food in the sea! Many species of seaweed have a lot to offer in both flavor and nutrition, with very low calories.
I’ve always lived hundreds of miles from the ocean, but my mother’s fondness for Asian-style cooking brought a little seaweed into my life! We used to get it mailed to us by my grandma in New York!
These days, many supermarkets across the United States carry some type of seaweed. Asian markets, health-food stores, and some online retailers offer a wide array of seaweeds.
Seaweeds are not animals, plants, nor fungi–they’re protists. Like plants, seaweeds convert sunlight into energy through the process of photosynthesis and convert carbon dioxide into oxygen. Unlike plants, seaweeds absorb nutrients and water through all their tissues instead of having a circulatory system.
Health Benefits of Seaweed
Let’s look at why you’ll want to slip some seaweed into your supper!
- Iodine is a critical nutrient that our bodies can’t make–we need to eat it so that our thyroid glands work properly to produce and regulate our hormones. The high iodine level in a traditional Japanese diet is believed to be one of the factors supporting the unusual good health of Japanese traditional eaters.
- Some seaweeds (such as kombu and dulse) are so high in iodine that they can be dangerous if eaten in large quantities, if you’re using medication or having medical procedures with iodine, or if you have thyroid nodules, hyperthyroidism, or autoimmune thyroid disease.
- If you’re anxious about overdoing iodine, serve seaweed with foods that inhibit iodine uptake, like broccoli, cabbage, bok choy, edamame, or tofu.
- Vitamin B12, necessary for proper iron absorption, is found in many animal foods but not in any plants . . . but remember, seaweed is not a plant! Although many seaweeds contain quite a bit of B12, there’s debate over whether our bodies can absorb it effectively. Don’t count on seaweed to supply all your B12, but it can give you a tasty boost!
- Other vitamins, antioxidants, and minerals vary among different types of seaweed, but all seaweeds collect nutrients from the ocean water.
- Digestive health is improved by seaweed’s fiber and polysaccharides, which feed “good” gut bacteria and increase the production of short-chain fatty acids that nourish the gut lining.
- Blood sugar levels can be stabilized by fucoxanthin, an antioxidant abundant in seaweed. That’s great news for people at risk for diabetes or obesity, and it explains why eating seaweed can prevent the post-party sugar crash!
- Satiation is the feeling of having had enough to eat. Seaweed is surprisingly satiating, considering its low calories. There’s a lot of anecdotal evidence of this, but science has yet to find a specific component of seaweed that has this effect. (So, don’t take alginate capsules–eat whole seaweed!)
- Umami is that awesome savory flavor that makes food fabulous! Many seaweeds–especially kombu and nori–are high in glutamates, amino acids that “bring out” the flavor in food. (Monosodium glutamate is a synthetic version. It’s safer to eat the real thing! But people who are sensitive to MSG might also feel funny after eating large amounts of seaweed.)
Seaweeds are abundant and quick-growing–up to two feet per day!–which makes them a very sustainable food source.
They grow without fertilizer or fresh water, counteract ocean acidification, and help control pollution by absorbing nitrogen and phosphorus. They don’t contribute to deforestation, erosion, or soil depletion.
Mark Sisson’s article on seaweed gives a clear and beautifully written explanation of why seaweed has so much to offer:
Living on a planet where the soil has been depleted by industrialized agriculture, we may need to turn to the sea to find the nutrients we need!
What’s Wrong with Seaweed Snacks?
Seaweed packaged for snacking has become popular in the past few years.
Each little plastic tray holds a dozen or so neat, crispy rectangles of flavorful, salty, paper-like sheets of nori seaweed, with significant fiber, Vitamins A and C, and a range of B vitamins–yet less than 50 calories.
The trouble with seaweed snacks is the packaging. To keep it crisp, each serving is sealed in a thick plastic+foil packet. To protect the delicate sheets from crumbling, they’re stacked in a plastic tray.
If you save money by buying a multi-pack, there’s another plastic bag around them all. None of this packaging is recyclable in most places! All of it adds to the single-use plastic choking our planet!
And there’s another problem:
Every single-serving seaweed snack includes a packet labeled DO NOT EAT. This contains silica gel, a desiccant, absorbing moisture from the air to keep the seaweed crisp. It’s not poisonous, but it’s a choking hazard because your body can’t dissolve or absorb it!
If you give a child a seaweed snack, first pick up all the seaweed and take out the desiccant packet from underneath. Put it in a safe place, out of reach of children and pets.
You can reuse desiccant packets to keep other things dry in storage. Here are more ideas. Once they’re in your home, you may as well use them before sending them to the landfill!
You can reduce packaging by buying the same type of seaweed (nori, also known as laver) in a larger, flat package with just one silica packet. Other varieties of dried seaweed also are packaged this way.
Not Just a Snack: How to Use Dried Seaweed in Meals
If you live near the ocean, you might be able to buy fresh seaweed or even harvest it yourself. But dried seaweed retains plenty of nutrition, and it’s quite convenient and easy to use.
Some types are ready to eat, while others need to be softened in warm water before use.
Sample a seaweed medley in a recipe like seafood seaweed coconut stew, or try one variety of seaweed at a time and get to know its special properties.
My local food co-op sells at least 6 varieties of dried seaweed, so I bought 4. The one I’d never tried using in my own cooking before is wakame.
This is the seaweed most familiar to Americans: thin, papery, black or dark-green sheets wrapped around sushi, maki rolls, and rice balls. Those tidy rectangles, with straight edges and even thickness, are not nori’s natural form: This seaweed is shredded finely and then pressed into sheets for drying.
A 9-inch-square sheet of nori has 80% of the Daily Value of Vitamin B12, 50% of Vitamin K, 25% of iodine, and 10% of Vitamin A. (Note that excess Vitamin K is dangerous to people with certain blood-clotting disorders.) Nori also contains zinc, copper, manganese, and selenium.
In addition to sheets of various sizes, nori is also available in small flakes–sometimes mixed with sesame seeds, fish flakes, or dried egg–to sprinkle on food. My family loves nori goma furikake on rice or on a buttered baked potato!
Nori isn’t just for Asian cuisine. Try it in this salmon soup!
Wakame (Sea Mustard)
Those dark-green ribbons floating in miso soup or served as the main ingredient of “seaweed salad” are wakame, a subtly sweet seaweed that is usually dried for sale, then boiled or steamed to a silky-yet-chewy consistency. (Even if it’s served cold, it’s been cooked.)
Here’s a summary of wakame’s health benefits, which include reducing cancer risk and balancing female hormones.
I made seaweed salad from this recipe–without the pepper flakes or cilantro–and it was delicious! The dressing has plenty of gingery flavor but doesn’t overwhelm the yummy taste of the seaweed. Wakame’s bouncy texture is pleasing once you get used to it. Both flavor and texture were better a day after making it.
Wakame is used in Korean as well as Japanese cuisine. Miyeok guk is a soup traditionally served to nourish new mothers recovering from childbirth. This quick and easy cold cucumber soup is great for summer!
Kombu is used mostly to enhance the flavor of other foods and as one of the main ingredients in dashi, the Japanese broth used as the base for many soups. Kombu simmered in soy sauce and mirin (rice wine) becomes a tasty cooked vegetable side dish.
Dried kombu is sold in big, rumpled, stiff strips. You can get “paper cuts” crumbling it in your hands! Most recipes tell you to soak it in warm water and then cut it up. If you need to cut dry kombu, it’s best to use scissors.
You’ll probably notice white “dust” on the surface of kombu. That’s mannitol, a sugar alcohol that occurs naturally and comes to the surface when the kelp is dried. It gives it a sweeter flavor.
I soaked a strip of kombu before using it in a recipe. Look how much bigger it is when it’s uncrumpled!
Whether you cook dry beans on the stovetop or in a slow-cooker or Instant Pot, adding a piece of kombu to the water when soaking and/or boiling beans releases the enzyme alpha-galactosidase, which helps to break down complex carbohydrates in the beans so you can digest beans more effectively and suffer less gas. It also helps the beans soften more quickly when cooking, which saves time and energy! Note: If you need canned beans in a pinch, you can actually buy them cooked with kombu seaweed.
Kombu is extremely high in iodine–depending on where it grew, it can have 20 to 120 times the Daily Value!
A serving of kombu also has as much fiber as two slices of whole-wheat bread. It has 13% of the Daily Value of magnesium and 11% of iron.
Quick-pickled vegetables make a delicious garnish or snack food! Add kombu to your quick pickles to enhance each vegetable’s own flavor while adding something special. (My family thought this recipe was okay, but we prefer the style of quick pickles in The Wanderlust Kitchen’s recipe for Bi Bim Bop.)
Kombu and shiitake mushrooms combine to make a delicious soup stock that’s a vegan substitute for fish broth as the basis for hearty soups. Try it in Japanese udon noodle soup! I did, and we were very happy with the flavor.
I just boiled a piece of kombu and 10 dried shiitake mushrooms in water while I cut up a sweet potato. Then I pulled out the kombu and mushrooms (with tongs), cut them up while the sweet potato started cooking, and put them back in along with some fresh ginger, soy sauce, and garlic. Later I added tofu and udon noodles.
Dulse (Sea Lettuce or Sea Parsley)
This beautiful dark-red seaweed is a great source of Vitamin B6, iron, and potassium. The iron is a type that’s difficult to absorb without Vitamin C–so eating dulse along with tomatoes or citrus fruit is a good idea. Dulse also is high in iodine, about 8 times the Daily Value.
My food co-op sells dulse flakes in a bulk bin, from which you can scoop into the container of your choice. I’ve used dulse flakes for years as an addition to marinara sauce, honey baked lentils, and soups. They’re so small that they’re barely noticeable. Reduce the salt in the recipe; like all seaweeds, dulse tastes saltier than its sodium content would predict.
Tiny dulse flakes are easy to sprinkle over any food to add savory flavor. Simply mix dulse into butter to make a delicious topping for toast or a baked potato! I made a smaller version of this recipe, 1 Tbsp. dulse in 1/2 stick of butter. Everyone in my family liked it but thought it was not much different from plain butter in flavor, although we did notice the little flakes of texture. Mixing in a little wasabi made it more exciting!
Can You Eat Too Much Seaweed?
Although most seaweeds are very high in iodine, this won’t be harmful to most people because about 90% of the iodine we ingest leaves the body in urine within a day or two. Just don’t eat seaweed at every meal! If you have any sort of thyroid problem, be cautious about eating large portions of seaweeds other than nori.
My main concern when I eat a lot of seaweed is that I’ll forget to eat enough total food! Because seaweed makes you feel full but is actually quite low in calories, if you’re mindful about not eating until you feel hungry, a high-seaweed diet might not maintain your weight.
I once had a weird moment during pregnancy when I ate a large bowl of miso soup generously laced with seaweed, and then I felt too full to eat anything else for two hours…during which I got dizzy and almost fainted because I had run out of calories!
Surprisingly, most varieties of seaweed seem to be almost immune to soaking up pollutants from the ocean. The one exception is hijiki, found to be high in arsenic. Still, you’ll want to avoid eating seaweed that grew in a particularly polluted part of the sea.
Dried Seaweed Sourcing Concerns
Seaweed farming has been going on for about 300 years and is a growing business worldwide.
This profile of a seaweed farmer shows how easy it is to grow seaweed in a selected location in the ocean and how valuable seaweed farms are as habitat for fish and shellfish who benefit from the cleaner water and higher oxygen levels created by the seaweed. Farmed seaweed is considered one of the most environmentally sustainable foods.
The nori and wakame I bought were farmed by Emerald Cove, which has a description of each farming practice on the back of the packet. The nori is certified organic. The kombu I bought was wild-harvested by Maine Coast Sea Vegetables; here are some details on their harvesting practices and organic standards.
Of course, farming in a specific area gives more control over pollution…but it’s still the ocean, so bad stuff can come drifting in! Organic standards require regular testing of both the growing conditions and the finished product. Wild harvesting by a conscientious company can be safe, too.
Is It Safe to Gather Your Own Seaweed?
Unlike picking wild mushrooms, seaweed foraging is pretty safe: No species of saltwater seaweed is poisonous. (However, some freshwater algae are dangerous.)
Some seaweeds are hard to digest, though, and can give you a stomachache! It’s best to learn about foraging before you start eating stuff washed up on the beach!
Also, be aware that clumps of seaweed lying on the beach may have broken loose from the roots days ago and begun to decay. Rotting seaweed won’t be so appetizing and might make you sick. Harvest just the fronds of seaweed growing on rocks and such, leaving the roots in place to grow new leaves.
Whether you gather it yourself or buy it from the store, seaweed can be a flavorful ingredient in your healthy meals!