The Top 7 Seaweed Benefits for Health

With evidence of its use as both food and medicine dating back to the Mesolithic period in countries like Japan, Korea, Chile, Ireland, and Iceland, seaweed has been a staple food for millennia, providing a vital source of essential micronutrients, fiber, and antioxidants.^1,2

Despite the use of seaweed in cultures around the globe, the U.S. has been slow to adapt to consuming this nutritional powerhouse. Although coastal Indigenous tribes like the Makah of the Pacific Northwest certainly utilized seaweed, it did not become mainstream in the U.S. until the health-conscious eras of the 1980s and 90s.³

If your only introduction to seaweed has been the little strip wrapped around your spicy tuna roll, you’re not alone—but there is a whole world of seaweed to be explored. In this article, we’ll dive into all the different varieties and seaweed benefits for health.

Edible Seaweed 101

There are a whopping 10,000 different species of seaweed living in our oceans, with 145 of these species being eaten today (mostly in Asia). However, an even smaller amount is commonly consumed around the world, with just a handful of species being the most popular. 

Although people often use “seaweed” and “kelp” interchangeably, they are not the same. Seaweed is in the algae family, and kelp is the largest subtype of seaweed. Essentially, all kelp are a type of seaweed, but not all seaweed is kelp.

In general, edible seaweed can be grouped into three categories: brown, red, or green seaweed—here are a few of the most commonly consumed types of each:

Brown Seaweed

Brown seaweed is olive green to brownish in color, often found in deep, cold waters and used in soups and broths. The most common types of brown seaweed include: 

• Kombu: The most iodine-rich seaweed, kombu is a type of kelp with an umami flavor most often used in Japanese soup broths called dashi. However, kombu has excessively high amounts of iodine, which can harm your thyroid. Eat kombu in very moderate amounts and always boil it first and discard the water to reduce its iodine content.
• Wakame: Wakame, more mildly flavored, is famously used in miso soup. It is also a type of kelp and most often comes dried in small strips that need to be rehydrated before use.
• Hijiki: Also called hiziki, this seaweed is savory and earthy (almost mushroom-like in taste) and comes in small, brown-black, twig-like pieces. 

Red Seaweed

With pinkish to deep red hues, red seaweed is the kind most often used in sushi rolls (it is red when it grows but turns deep green during the drying and roasting process), with types including:

• Nori: Red nori is the type you see adorning sushi rolls and found in seaweed snack packs or sheets. 
• Dulse: Dulse is most commonly consumed in dried or flaked form and has a salty and slightly smoky flavor. 
• Irish Moss (Sea Moss): Sea moss gel has seen a huge uptick in popularity in the past couple of years, with its name indicating its long history of use in Ireland.

Green Seaweed

Green seaweed is less consumed, with its bright green varieties originating in shallow waters and often used in fresh seaweed salads. Just like green plants growing on land, green seaweed contains chlorophyll. 

• Green Nori: Green nori is a different species than red nori, with its finer texture leading to its use as flakes or powder rather than seaweed sheets.
• Sea Lettuce: Like its land-based counterpart, sea lettuce looks quite a bit like a green leafy lettuce, which can be eaten dried, raw, or cooked.

Now, let’s take a look at some of the leading health benefits of seaweed.

Top Seaweed Health Benefits

1. High in Nutrients and Antioxidants

The wide-ranging types of seaweed vary in their nutritional value, but all are nutrient-dense superfoods packed with vitamins, minerals, and antioxidants. Some of the key nutrients found in seaweed include:

• Iodine (kombu, wakame, and other brown seaweeds have the highest)
• Iron
• Magnesium
• Potassium 
• Vitamin B12 (mainly nori) 

Seaweed also contains plentiful antioxidants, helping to fight oxidative stress that leads to disease development and aging.⁴ The prominent antioxidants include fucoxanthin (found mainly in brown seaweed), phycocyanin (red seaweed), chlorophyll (found in green and red seaweed), and flavonoids.⁵

2. Supports Heart Health

The antioxidant content and anti-inflammatory potential of seaweed make it beneficial for cardiovascular and metabolic health, including supporting healthy blood sugar and lipid levels.

One meta-analysis from 2023 concluded that brown seaweed consumption significantly reduced post-meal blood glucose, markers of insulin resistance, and hemoglobin A1C levels (a 3-month average of blood sugar).⁶

3. Brain Health

Green, red, and brown seaweed have all been found to have therapeutic potential for brain and cognitive health.

One review paper states that these seaweeds may be beneficial for preventing neurodegenerative conditions, including Alzheimer’s and Parkinson’s diseases.⁷

Dozens of bioactive compounds in seaweed play a role here, including antioxidants, minerals, terpenes, polysaccharides, phycocolloids, sterols, phycobilins, and phycocyanins.⁸ 
One polysaccharide compound called fucoxanthin (found in brown seaweed like wakame) is thought to benefit cognitive health by reducing neuroinflammation and oxidative stress in the brain.⁸

4. Skin Health

The anti-inflammatory and antioxidant effects of seaweed also support skin health. While there has been a rise in seaweed in topical skincare, consuming seaweed may also benefit skin appearance and certain skin conditions.

One study found that brown, red, and green seaweed improved symptoms of atopic dermatitis, also known as eczema.⁹

It’s thought that seaweed helps with eczema because it improves skin barrier function, modulates immune responses, and reduces epidermal thickness (a symptom that can occur with chronic eczema).⁹

5. Healthy Thyroid Function

Food from the sea (including sea vegetables and seafood) are the best natural dietary sources of iodine, a mineral essential for healthy thyroid functioning. Thyroid issues like goiter are commonly seen in regions with iodine deficiency, which led to many countries introducing iodized salt.

That said, iodine consumption and the thyroid are kind of a “Goldilocks” situation—you don’t want to undereat or overeat it, as excessive iodine intake can cause either hypothyroidism or hyperthyroidism.¹⁰

In general, brown seaweed varieties have more iodine than red or green seaweed. Just 1 gram of kombu kelp (less than a teaspoon) contains over 20 times the recommended daily intake of iodine and almost 3 times the upper limit for safe consumption.¹⁰

However, kombu is typically not eaten whole—it’s usually used to flavor dashi stock and then discarded. If you boil kombu and discard the water, it reduces the overall iodine content. 

Overall, if you already have a thyroid condition, ask your doctor or endocrinologist if you are unsure if you should eat seaweed or stick to red and green seaweed.

6. Gut Health

Several polysaccharides that are unique to seaweed—including fucoidan, laminarin, alginate, ulvan, and porphyran—act as prebiotic fibers, which provide fuel for our healthy gut bacteria to survive and thrive on.¹¹ 

More prebiotic fibers in the digestive system benefit our gut microbiome, which supports digestion and other aspects of health.

7. May Help Weight Management

Several of the bioactive compounds, polysaccharides, and antioxidants found in seaweed have been shown to help with weight loss or management.¹²

One study looked at fucoxanthin supplements—a polysaccharide prebiotic fiber found in brown seaweed. The researchers found that mildly obese people who took 3mg per day of fucoxanthin had significant reductions in body weight, BMI (Body Mass Index), and visceral fat compared to a placebo group.¹³ 

Research published in Nutrients concluded that macroalgae like seaweed help to reduce obesity by increasing fatty acid oxidation and thermogenic capacity, essentially elevating fat burning and metabolism. The researchers also suggest that the healthier gut microbiome from eating seaweed also contributes to lower body fat.¹² 

Seaweed Benefits FAQs