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Is Seaweed Good for You?
Updated on September 13, 2023
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Diet / Weight Loss
Is Seaweed Good for You?
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Seaweed is definitely good for your health. However, like with all things, it should be taken in moderation.

Seaweed has been consumed in many parts of the world for years for its health benefits and high nutritional value.

It has many essential nutrients, such as vitamins, minerals, and antioxidants. It’s an excellent alternative source of protein, too.

What is Seaweed?

Is Seaweed Good for You? 2

Seaweed is a common name referring to various kinds of algae and marine plants. They thrive on the rocky shores of oceans and seas around the world.1 Many of their species are edible.

Edible seaweeds are a key ingredient in many Asian dishes, such as sushi, salad, and stews. It’s recently gained popularity in Western cuisine as well.

What Makes Seaweed Healthy?

Seaweed is healthy because it contains different vitamins, minerals, and other nutrients like antioxidants. These nutrients help support a number of body functions, like hormone production and digestion.

How Does Seaweed Support Thyroid Function?

Seaweeds support your thyroid health by supplying the thyroid gland with essential minerals—iodine and tyrosine—it needs for hormone production.2,3

Iodine is a mineral, and tyrosine is an amino acid. Your thyroid uses iodine and tyrosine to make thyroxine and triiodothyronine. These hormones help manage your metabolism.4

Good thyroid function relies on an adequate amount of these hormones to prevent a condition called hypothyroidism.

Since your body doesn’t make iodine, you must rely on foods to meet your iodine needs. An iodine deficiency may lead to symptoms like fatigue, neck lumps, and excess weight gain.5 

Seaweed is among the food sources that can help you get enough iodine.

Vitamins and Minerals in Seaweed

Seaweed contains nutrients, which vary depending on the type. Eating seaweed is an easy way to get your fill of many forms of vitamins and minerals, including the following:

  • Vitamin A
  • Vitamin B1
  • Vitamin B2
  • Vitamin C
  • Vitamin E
  • Vitamin K
  • Calcium
  • Copper
  • Folate
  • Iron
  • Potassium
  • Manganese

Some edible seaweeds are also a good source of vitamin D and B12, which are rare in plant foods.

Antioxidant Properties of Seaweed

Seaweed has antioxidant properties in the form of Vitamins C and E. Antioxidants are substances that can give electrons to free radicals.6

Free radicals are unstable molecules that can cause damage to your cells. Antioxidants neutralize free radicals by donating electrons to them, protecting your cells from damage.6

In addition to these vitamins, seaweed also contains a plethora of plant compounds that have simultaneous substantial antioxidant benefits, such as:

  • Carotenoids – offer protection from different diseases by boosting your immune system7
  • Polyphenols like catechins, flavonols, and phlorotannins – help fight oxidative stress and inflammation and avoid certain types of cancer8
  • Phlorotannins – have promising health benefits, including antioxidant, antibacterial, anti-diabetic, anti-inflammatory, anti-cancer, and so on9

Many studies focus on the primary carotenoid in seaweeds, fucoxanthin, which contains 13.5 times the antioxidant potency of vitamin E.10 

Seaweed's Role in Gut Health

Adding seaweed to your diet can help improve gut health by promoting a balanced gut microbiome.

First, seaweed is a good source of fiber. Fiber is essential to your gut health because it helps good gut bacteria thrive by providing their food.

Seaweed has more fiber content than most fruits and vegetables since 25 to 75 percent of its dry weight is from fiber.11 

Second, seaweed contains sugars—sulfated polysaccharides—that promote the growth of beneficial bacteria in the gut. These certain sugars aid the production of short-chain fatty acids (SCFA).12

SFCAs help fortify the lining and protect against harmful bacteria by nourishing the cells in your gut lining.

Seaweed is also a good source of prebiotics. Prebiotics act as food for good bacteria located in the gut to thrive.

Seaweed and Weight Management

Seaweed can help manage your weight since it’s an excellent source of natural fiber

Several studies show that fiber naturally present in food can slow down gastric emptying, which helps you feel full for periods.13

Aside from fiber, seaweed contains fucoxanthin, a plant compound that may encourage weight loss. Studies have shown that it can boost your metabolism and reduce your body’s accumulated fat.14

Seaweed is also low in calories. You can freely incorporate them into your meal plans without worrying about exceeding your calorie intake.

This can help you achieve a calorie deficit by reducing your calorie intake. Creating a calorie deficit is one of the many ways to lose weight efficiently.

Seaweed's Impact on Blood Sugar Management

There’s a potential link between seaweed and improved blood sugar control.

One study shows that taking seaweed supplements has a favorable effect on the blood sugar levels of people with type 2 diabetes.15

Another study demonstrates that seaweed helps increase insulin sensitivity. Insulin is a hormone that helps your body process glucose for energy.16

When your insulin sensitivity is enhanced, your body can better utilize glucose, which can help reduce your blood sugar levels. Aside from this, it also has an effect on lowering blood lipids.

Despite the promising findings, scientists need to conduct more studies to further confirm these health benefits of seaweed.

Are There Different Types of Seaweed?

Yes, seaweed has many different types. They have three classifications based on their pigmentation: brown seaweed, red seaweed, and green seaweed.

Brown Seaweeds

Brown seaweeds are a group of algae with an appearance of a spectrum from brown to olive green. They are multicellular organisms.

The amounts of chlorophyll and fucoxanthin they contain determine their color. They come in various sizes and shapes, with roughly 1,500 different species.

Most brown algae inhabit colder coastal areas. They might be free-floating or anchored to a layer of rock or soil (substratum).

The following are some common brown seaweeds:

  • Ectocarpus – a non-parasitic alga that thrives on another plant
  • Fucus – found attached to rocks
  • Sargassum – a free-floating type of brown algae

Red Seaweeds

Red seaweeds are a group of algae that lives in different aquatic habitats, mostly tropical seas or marine. Only a few species live in freshwater environments.

The pigments phycoerythrin and phycocyanin mask the chlorophyll in red seaweeds, resulting in their red appearance.

Red seaweed can thrive in deeper waters where green seaweeds may not flourish. It’s because their pigments allow them to photosynthesize in lower light levels.

Plants undergo photosynthesis to convert nutrients from carbon dioxide and water into energy using sunlight.

Common examples of red seaweeds include:

  • Nori – the most well-known edible dried red seaweed
  • Dulse – generally found on the rocky northern shores of the Atlantic and Pacific oceans
  • Agar – is used to make gelatin and can also serve as a stabilizing and thickening agent
  • Carrageenan – is used as an additive to emulsify, thicken, and preserve foods

Green Seaweeds

Green seaweeds are the most diverse algae, with at least 7,000 identified species. About 800 kinds of green seaweeds are found in aquatic environments, specifically saltwater habitats. 

The rest of the green seaweed species flourish in terrestrial and freshwater environments. Some can make their homes on soils or tree trunks or develop symbiotic relationships with fungi and animals.

Green seaweeds need to absorb sunlight and transform it into food (glucose) to thrive. Because of this, they are less likely to live in deeper waters.

Some examples of well-known green seaweeds are:

  • Sea lettuce (Ulva lactuca) – known for its leaf-like structures that resemble garden lettuce
  • Aonori (Green laver) – often used as a garnish and has a mild, slightly salty flavor
  • Mermaid's hair (Codium fragile) – has a felt-like appearance and slimy texture

Does Eating Seaweed Have Side Effects?

It’s generally safe to eat seaweed. But there are a few potential side effects you should be aware of.

The side effects can vary according to the type of seaweed, the amount you consume, and your overall health.

Excess Iodine Intake

Seaweed is abundant in iodine, a mineral essential for thyroid function.

However, too much iodine in your body from excess seaweed consumption can cause hyperthyroidism.17

Hyperthyroidism is when the thyroid gland produces too many thyroid hormones. Symptoms include weight loss, palpitations, and sleeping difficulties.

Since seaweed can absorb iodine from seawater, those varieties gathered from tropical oceans will have more iodine content than those found in other bodies of water.

For instance, kelp and nori contain more iodine than other varieties because they are commonly grown in tropical oceans.

If you plan to include seaweed in your diet, knowing how much iodine it contains is essential to ensure you are only getting enough.

Heavy Metal Contamination

Heavy metals occur naturally in the environment and are vital to life. But they can become toxic when they accumulate in living things. Some heavy metals like cadmium, lead, and aluminum are toxic even when ingested in small amounts.

Seaweed can accumulate heavy metals in their environment and may pose a health risk.18 

The amount of heavy metals they take depends on the seaweed type, the location where it was grown, and the processing method used.

Heavy metal exposure can cause several symptoms and health concerns, including:

  • Headaches
  • Tremors
  • Difficulty concentrating
  • Diarrhea
  • Nausea
  • Vomiting
  • Kidney damage and failure
  • Liver damage and failure
  • Increased risk of certain cancers

Allergies and Sensitivities

Seaweed allergies and sensitivities are rare but not unheard of. A reaction to seaweed can be triggered by skin contact or through consumption.

Studies have identified the phlorotannins, polysaccharides, and proteins in seaweed as possible allergens.19

The common symptoms of seaweed allergy and intolerance may include one or more of the following:

  • Skin irritation, such as rash or hives, itching, blisters
  • Nausea
  • Vomiting
  • Diarrhea
  • Abdominal pain
  • Wheezing
  • Shortness of breath
  • Difficulty breathing
  • Drop in blood pressure

Seaweed in Different Cuisines

Many cultures have incorporated edible seaweed into their cuisine because of its versatility. It's a kitchen staple in many Asian cuisines but has recently found its way to different Western dishes.

Seaweed in Asian Cuisine

In Asian cuisine, particularly in Japan, Korea, China, and other East Asian countries, seaweed is essential. It is commonly added to dishes like sushi, miso soup, and tempura. 

Seaweed in Western Cuisine

In Western cuisine, seaweed is a main ingredient in salads, soups, and snacks.

They are also used in baking for additional flavor. For instance, the Irish add dulse to their Irish soda bread, while the Welsh make their laverbread from boiled seaweed.

How to Incorporate Seaweed into Your Diet

You can get creative with including seaweed in your meals since it’s a flexible ingredient. Here are some ideas for how you can incorporate seaweed into your diet.

Seaweed Snacks

Using seaweed to replace traditional snacks completely changes your whole snacking experience.

Seaweed snacks like seaweed chips or crisps are made by adding flavors to dried seaweed. They can replace less-healthy foods, like chips and cookies, with empty calories.

Seaweed Salads

If you enjoy making a salad, then you’d definitely love fresh seaweed salads.

Enjoy eating fresh seaweed salad by combining it with other ingredients, such as vegetables, fruits, and nuts. You can dress it with vinaigrette or soy sauce dressing for a more savory flavor.

Cooking with Seaweed

There are different ways to include seaweed in your cooking, depending on the seaweed type and desired result.

Dried Seaweeds

Try dry seaweeds first if you’re just getting started with incorporating seaweeds into your diet. They’re widely available, and you can store them for periods since they have a long shelf-life.

Dried seaweeds can be used to prepare stocks with a savory umami flavor. Add them to your soups, salads, deviled eggs, and other dishes.

Some of the usual dried seaweeds used for cooking are:

  • Nori – made from minced, pressed, and roasted red seaweed
  • Hijiki – its tiny, black, twig-like appearance resembles tea leaves
  • Wakame – commonly used in miso soups
  • Dulse – often added in Irish bread and pudding

Fresh Seaweeds

Unlike dried seaweeds, you need to cook fresh seaweeds immediately because they are perishable. They have more water content, making them more prone to spoilage.

Fresh seaweeds make a good side dish to seafood meals or soups. Some recipes include quickly deep-frying them for up to 20 seconds for a light and appealing side.

But some seaweed varieties are delicate and best prepared tenderly or eaten raw, like sea lettuce. Sea lettuce has a sheet-like structure, which you can also use to wrap fish before cooking for an added sea flavor.

Updated on September 13, 2023
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19 sources cited
Updated on September 13, 2023
  1. Everything You Need to Know About Seaweed.” American Oceans.
  2. Seaweeds as a Source of Functional Proteins.” Phycology.
  3. Iodine.” Harvard T.H. Chan School of Public Health.
  4. Chapter 3: The Thyroid Gland.” Endocrinology: An Integrated Approach.
  5. Iodine Deficiency.” Cleveland Clinic.
  6. Understanding Antioxidants.” Harvard Health Publishing.
  7. Carotenoid composition and antioxidant potential of Eucheuma denticulatum, Sargassum polycystum and Caulerpa lentillifera.” Heliyon.
  8. Potential Role of Seaweed Polyphenols in Cardiovascular-Associated Disorders.” MDPI.
  9. “Antioxidants From The Red Algae Kappaphycus Alvarezii.” Marine Antioxidants.
  10. Biosynthetic Pathway and Health Benefits of Fucoxanthin, an Algae-Specific Xanthophyll in Brown Seaweeds.” International Journal of Molecular Sciences.
  11. Prebiotics from Marine Macroalgae for Human and Animal Health Applications.” MDPI.
  12. Digestibility Of Sulfated Polysaccharide From The Brown Seaweed Ascophyllum Nodosum And Its Effect On The Human Gut Microbiota In Vitro.” National Center for Biotechnology Information.
  13. The Role of Fiber in Energy Balance.” Journal of Nutrition and Metabolism.
  14. Brown Seaweed Contains Promising Fat Fighter, Weight Reducer.” American Chemical Society.
  15. Effects Of Seaweed Supplementation On Blood Glucose Concentration, Lipid Profile, And Antioxidant Enzyme Activities In Patients With Type 2 Diabetes Mellitus.” Nutrition Research and Practice.
  16. Antioxidant and Antidiabetic Activity of Algae.” MDPI.
  17. Iodine, Seaweed, and the Thyroid.” European Thyroid Journal.
  18. Atomic Spectroscopy-Based Analysis of Heavy Metals in Seaweed Species.” Applied Sciences.
  19. Edible Algae Allergenicity – A Short Report.” Journal of Applied Phycology.
Cristine Santander
Cristine Santander
Content Contributor
Cristine Santander is a content writer for KnowYourDNA. She has a B.S. in Psychology and enjoys writing about health and wellness.
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