Sea Greens 101: Types, Benefits, Where to Buy Them, and More

Medically Reviewed
Seaweed nori irish moss kombu sea greens
If you've only ever had seaweed in sushi, you may be surprised at how many varieties there are — and how good they are for you!Adobe Stock

When you were little, your parents probably told you it’s important to “eat your greens.” And while they may have been thinking of greens grown in soil, it turns out greens from the sea are just as beneficial — and they’re a food trend for 2022 in the United States (though they’ve long been a staple of certain cultures and regions around the world).

“Sea greens or sea vegetables are simply edible plants, such as seaweed and algae, that come from the sea,” says Vicki Shanta Retelny, RDN, of Chicago, the author of The Essential Guide to Healthy Healing Foods and host of Nourishing Notes podcast. They can be a nutritious and tasty addition to your diet. This guide will tell you everything you need to know about sea greens, why you should add them to your next meal, and creative ways to do just that.

Common Questions & Answers

What are sea greens good for?
Sea greens add nutrition to your meal, including vitamins A, B, and E. They are also one of the few vegetarian sources of omega-3 fatty acids, which have been associated with heart health and may help protect against a number of chronic illnesses. You’ll also get added flavor, which can vary, depending on what type of sea green you choose.
Which sea greens are edible?
Most types of sea greens are edible, when cooked or prepared properly. Nori, Salicornia, dulse, kombu, wakame, sea purslane, and Irish moss are all popular, edible sea veggies.
What are some of the healthiest sea vegetables?
Good news: Most sea veggies are very healthy (unless they have been harvested near a place with contaminated water). Nori, spirulina, Salicornia, and dulse, kombu, wakame, sea purslane, and Irish moss are common and very healthy sea veggies.
How can I use sea greens?
You can use sea greens as wraps for sushi and salads, as an addition to smoothies and oatmeal, or as a topping for your main dish. Salicornia (also known as “sea beans”), for example, can be eaten as an alternative to a salad.
Are there any risks to eating sea veggies?
Although sea greens can add a healthy dose of nutrition to your meals, there are risks if you consume too many. You might take in too many heavy metals or too much of the mineral iodine, which can affect your thyroid. If you harvest sea veggies and then do not properly wash them you could get sick.

What Are Sea Greens?

As their name implies, sea greens are types of plants or algae that grow in or near the ocean, according to the Smithsonian.

These healthy sea vegetables are like veggies on land, according to the University of California in San Diego (UCSD), in that they require sunlight, nutrients, and water to grow.

You can even harvest the sea vegetables yourself to cook with, UCSD notes (and you don’t need a license to do so, although it is a good idea to check with local wildlife authorities before harvesting). Their pro tip: Harvest fresh seaweed (not what’s been washed up on the sand) and always rise off your sea greens, in case there was any contamination in the water. Avoid areas that are likely to be contaminated as well: Sea greens harvested from water that is near sewage outfalls or storm drainage pipes, for example, can contain pathogenic microbes like Escherichia coli or Vibrio parahaemolyticus.

Sea vegetables offer other perks, too. “Sea greens are vegan and gluten-free and considered a ‘superfood’ because they contain several antioxidants and are a good source of fiber,” says Shilpi Agarwal, MD, a board-certified physician in Washington, DC.

Potential Health Benefits of Sea Greens

There are many good reasons to add sea greens to your diet. “Sea greens are highly nutritious, as they are loaded with vitamins and minerals, such as potassium, calcium and magnesium, as well as iron and iodine,” says Retelny.

A review of research in the Journal of Applied Phycology

points out that sea veggies are a good source of the ever-important B-group of vitamins, as well as vitamin A and vitamin E. Vitamin A is crucial for vision and your immune system, according to the National Institutes of Health (NIH)

, and vitamin E is essential for everything from your blood to your brain to your skin.

Kelp, for example, has 70 micrograms (mcg) of beta-carotene in 100 grams (g), or about ? of a cup (and your body converts beta-carotene into vitamin A), according to the U.S. Department of Agriculture (USDA).

You’ll also get 1.3 g of fiber, 89 milligrams (mg) of potassium, and 168 mg of calcium.
Wakame, meanwhile, has a whopping 216 mcg of beta carotene in about ? of a cup, as well as 1 mg of vitamin E, 150 mg of calcium, and 107 mg of magnesium.

And a type of seaweed called agar contains small amounts of the vitamin B6 (0.03 mg) in about ? of cup, plus 226 mg of potassium and 54 mg of calcium.

A word of caution, though: “Care must be taken not to over consume iodine from sea greens,” says Retelny. Per NIH, too much iodine can affect how your thyroid functions, leading to a variety of problems, including hypothyroidism. In most cases, it is hard to exceed the upper limit of 1,100 mcg per day from food and supplements, but two tablespoons (tbsp) of dried flaked nori, for instance, provides more than 100 mcg.

In addition, sea greens can also contain beneficial dietary fibers called polysaccharides, according to a study published in Marine Drugs.

These fibers can work as prebiotics to potentially help maintain a person’s gut bacteria, which is beneficial for one’s health and well-being, the researchers note. “The health benefits of sea greens also appear to be related to constipation and improving bowel regularity,” says Dr. Agarwal.
Another perk? You’ll also load up on beneficial omega-3 fatty acids. One study (done in a laboratory setting) found both red and brown seaweed could be a valuable source of fatty acids, including omega-3s. Eaten on their own or used as an ingredient in dietary supplements and other products, these sea greens could be a great vegan source of these healthy fats.

Omega-3s are essential fatty acids that help everything from your heart to your immune system and lungs function at their best.

Additionally, research published?Antioxidants

found that adding brown seaweed to rye snacks upped the antioxidant levels of the snacks. The researchers note that this shows that sea greens can potentially be used as a natural ingredient to improve the health of consumers. (As a reminder, antioxidants are natural substances that can delay — or even prevent — cell damage in the body, according to the NIH.)

Still, not all sea greens are created equal. “Vitamin, mineral and antioxidant content in sea greens is highly variable based on their marine environment, and more,” says Retelny.

Types of Sea Greens

Just like there are many different types of “land greens,” like arugula, spinach, and kale, there are many types of sea greens and algae. Here are some common varieties.

Kelp is a type of brown algae. There are three different varieties of algae — brown, red and green, explains Retelny. “The largest are brown algae, such as kelp and they tend to contain the most iodine.” And iodine is a crucial nutrient that helps your thyroid make important hormones, according to the Academy of Nutrition and Dietetics.

Salicornia is also called “sea bean” and has a similar crunch factor to the green bean (though they are in no way related).

Dulse is a red algae that grows in the Atlantic as well as the Pacific ocean, and has a salty flavor, which makes for a great addition to snacks like popcorn, and you can often buy it in flakes.

Nori is the go-to sea vegetable for sushi, and USDA data shows that the algae has protein and beneficial vitamins like C and K, and compounds (including taurine, which can help prevent gallstones).

Spirulina is a green algae that’s found in both oceans and salty lakes, according to the Cleveland Clinic, and is typically sold as a powder or in supplement form.

Like nori, it also contains protein, plus is a good source of B vitamins, they note, which can help with your metabolism as well as your immunity. For example, 1 tbsp of spirulina has 4 g of protein, which is almost 13 percent of your daily value.

Other popular varieties of sea vegetables include kombu, wakame, sea purslane, and Irish moss.

Sea Greens and Weight Loss

While they are no magic bullet for slimming down, sea greens do have a few properties that are beneficial if you’re trying to shed pounds. “They’re relatively very low in calories, so they can be a good addition to your diet if you are aiming to lose weight,” says Agarwal. One strip of dried seaweed has just 1.5 calories.

Like land vegetables, sea greens also tend to have some fiber, which has been shown to help with satiety and weight loss and maintenance. “Sea greens may be effective for weight loss or management due to their prebiotic fiber content,” says Retelny. “Fiber not only fills you up, but these types of prebiotic fibers can feed the beneficial bacteria in the gut, and a healthy microbiome may help prevent weight gain,” she says. For example, a?review of research in?Preventive Nutrition and Food Science, discovered that a healthy gut microbiome affects how calories are burned and nutrients are broken down in the body.

How to Eat Sea Greens

Because there are so many types and forms of sea greens, there are a lot of different ways to incorporate them into your diet. “You can add seaweed to soups, sauté sea greens with a hint of oil and seasoning, use nori sheets instead of tortillas or wraps, and use nori flakes in salads, soups, and scrambled eggs,” suggests Retelny. Some research has found that processing treatments may potentially impact the nutritional value of nori sheets, but new technologies may help limit this, the researchers note.

Seaweed also comes in powder form that you can add to your breakfast. “You can use powdered spirulina in smoothies, as well as blend it with yogurt or warm oatmeal,” says Retelny.

Recipes With Sea Greens

For a creative take on sea greens, try these Nori Salad Wraps from the Kitchen Paper. In addition to the good-for-you nori, they’re also loaded with other healthy veggies like cucumbers, carrots, and red cabbage.

If you’re looking to switch up your smoothie game, this Green Spirulina Smoothie from Minimalist Baker has you covered. With just five ingredients, it’s simple to make, and comes with healthy additions like cucumber, banana, and kale.

And if you want a simple and delicious recipe for Salicornia (aka sea beans) check out this recipe for Sea Bean Salad from chef Hank Shaw. The sea beans are the main event, tossed with garlic, olive oil, and red pepper flakes, along with a little lemon and feta cheese.

Also, sea greens are increasingly popular in powdered and supplement form. They can come in blends, too, with a variety of sea greens combined into one pill or powder. It’s important to know, though, that supplements aren’t regulated by the FDA, so talk with your doctor before you start a regimen.

Other Uses for Sea Greens

You may have noticed that some of your favorite beauty products boast on the label that they contain sea greens. And that can be a good thing!

“Seaweed is used in skincare products, as it has bioactive, anti-inflammatory, and moisturizing compounds,” says Retelny. One review of research found that seaweed can be used as an ingredient in skin-care products to help with everything from moisturizing to anti-acne and even anti-aging.

Researchers at Newcastle University (in partnership with Proctor and Gamble) have found a way to use sea greens in laundry detergent, to make a more sustainable and eco-friendly product.

Side Effects of Sea Greens

Sea vegetables do contain iodine, and while it’s an important trace mineral to include in your diet, too much can be a problem. “Excessive iodine intake can cause thyroid problems,” says Retelny. Adults only need 250 mcg a day, and should not exceed 1,100 mcg.

Sea greens can contain a lot of iodine, so anyone with thyroid disease or who takes thyroid medicine should be careful, says Agarwal. In fact, it’s best for anyone to be cautious when it comes to regularly consuming sea greens, or products or supplements that include them, because you can easily exceed the recommended limits for iodine. In one case study a woman who drank an herbal tea containing kelp developed hyperthyroidism due to the excess iodine.

Another potential side effect? “Sea greens can contain heavy metals, and although toxicity is rare, if you eat sea greens daily it can build up over time,” Retelny says. A study in the journal Chemosphere found that some sea green products had high levels of heavy metals and didn’t label the amounts of iodine correctly on the packaging, which could pose health risks.

Where to Buy Sea Greens

Fortunately, you don’t have to look too hard to find sea vegetables in your local grocery store. “Sea green–infused products are everywhere now, from puffed chips to hot sauce to spice blends to frozen kelp cubes,” says Retelny. “You can purchase them online, or most grocery stores carry sea green enhanced products — it’s just a matter of scouting them out,” says Retelny. And research shows that processing, especially heat, can reduce the antioxidant compounds in the sea greens, so it’s important to know that you might not be getting the most out of your sea greens when you buy them in a super-processed form.

If you do buy a product that boasts it’s made with sea greens, you’ll still want to make sure it’s an overall healthy food. “It’s always a good practice to check food labels and see what other ingredients are in the products you are buying,” says Retelny. Also, basic is best, when it comes to getting the most out of sea veggies. “Try to purchase sea green products with minimal ingredients, such as dried, roasted nori sheets,” Retelny advises.

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