Why Seaweed is Amazing!

March 17, 2016 in Categories: , by

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SushiCreative chefs have long known that seaweed is a tasty vegetable that can liven up a meal. But, it just so happens to be one of the most nutrient-dense plant foods as well! Seaweed is teeming with essential minerals, carotenoids, and even long-chain omega-3 fatty acids, making it a powerful addition to our diets. In fact, the benefits of seaweed are even greater than most of us realize. Let’s take a closer look at this amazing food!

Types of Edible Seaweed

Most of us are familiar with the nori that wraps sushi rolls, but list of edible seaweeds definitely doesn’t end there. Other types of seaweed fit for human consumption include:

  • Seaweed_SaladDulse, a salty red seaweed that can be eaten without any soaking or cooking!
  • Kombu, a thick seaweed often used as a flavor enhancer in broth and a tenderizer for beans
  • Arame, a mild-flavored seaweed high in lignans
  • Wakame, a subtly sweet seaweed often used in soups and salads (especially the seaweed salad found in Asian restaurants)
  • Laver, a smooth, sheet-like red algae with a very high iodine content (which makes its flavor similar to olives and oysters!), which is used to make nori for sushi

I have dried versions of all of the above in my pantry at all times!

A Nutrient Superstar

Plenty of vegetables have impressive nutritional résumés, but seaweeds really take the cake (er, the salad)! Although each variety of seaweed has a different overall profile of vitamins and minerals, in general, you can expect these foods to be rich in:

  • Iodine
  • Calcium
  • Magnesium
  • Iron
  • Potassium
  • Phosphorus
  • Manganese
  • Copper
  • Chromium
  • Zinc
  • Selenium
  • Vitamin C
  • Vitamin E
  • Vitamin K
  • B vitamins (B1, B2, B3, B5, and B6)
  • Dozens of additional trace minerals! (this may be one of the more compelling reasons to include seaweed in our diets as many of these important minerals are hard to find in the modern food supply)
  • In the case of algae, DHA (an omega-3 fat not found in many plant foods)

On top of all that, seaweeds have some special components that aren’t found in any land-based vegetables, and which may be responsible for some of their unique health benefits:

  • Fucoxanthin, a type of carotenoid that gives seaweeds a brown pigment, and which has potent anti-cancer properties, the ability to reduce liver fat and liver enzymes, and the potential to boost metabolic rate and assist in fat loss!
  • Fucoidans and laminarins, sulfated polysaccharides that have been shown to induce cell death of certain cancers (such as lymphoma), have antiviral and neuroprotective properties, help slow blood clotting, and may help modulate the immune system (although in most of these cases, more research in humans is needed to know for sure).
  • Alginates, cell-wall constituents of brown algae that may help in weight loss, glycemic control, and appetite regulation.

Anti-Inflammatory Effects



Numerous studies have shown that some components in seaweed help fight inflammation! The fucoxanthin in seaweed is the biggie here: it can inhibit nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) protein expressions, and also suppress the production of a variety of inflammatory cytokines (like IL-1β, TNF-α, and IL-6). That might sound like a lot of complicated science, but basically, it just means that the carotenoid in seaweed can tank pro-inflammatory mediators and help reduce excessive inflammation in the body. (Of course, that has a risk-lowering effect for the numerous conditions that stem from chronic inflammation, too!)

Seaweed May Fight Heart Disease


Dried Kombu

Among seaweed’s many perks is the potential to cardiovascular health! The antioxidant and anti-inflammatory properties of fucoxanthin can help thwart multiple processes involved in the progression of heart disease, while also modulating immune function. And, research has shown that a many seaweeds have hypolipidemic (lipid-lowering) activity, helping reduce levels of triglycerides and LDL cholesterol. And, the DHA found in algae and algal oil can not only reduce triglycerides and LDL cholesterol, but also raise HDL cholesterol—which, collectively, paint a more favorable picture for combating heart disease!

Seaweed for Cancer Prevention and Treatment



In Traditional Chinese Medicine and Japanese folk medicine, seaweeds have long been used to treat tumors, and Western science is beginning to discover why! Multiple studies have shown that seaweed can increase apoptosis (programmed death) of tumor cells, prevent the growth of new blood vessels that supply tumors, inhibit tumor cell adhesion, and prevent metastasis. Whew! That’s a pretty impressive lineup, huh? And, even small amounts of seaweed seem to have a big effect. In one study of postmenopausal women, consuming just 5 grams of brown seaweed each day resulted in a 50% drop in a type of receptor that’s over-expressed in cancer (urokinase-type plasminogen activator receptor, or uPAR, which is involved in multiple signaling pathways, cell adhesion, inflammation, immune function activation, tissue repair, and a number of other functions). The key players behind seaweed’s anti-cancer effects may be its fucoxanthin content, its polyphenolic compounds, its sulfated polysaccharides (fucoidan and laminarin), its ability to increase the colon’s protective mucus bilayer, and its ability to bind dietary toxins and carcinogens by increasing stool bulk.

In fact, the traditional use of seaweed in some parts of Asia (like Japan) may help explain why those areas have much lower rates of certain cancers (especially breast cancer) than most Westernized nations!

Antiviral Properties of Seaweed



Another incredible feature of seaweed is its antiviral potential. The sulfated polysaccharides in seaweed can block the interaction between many viruses and host cells—including important pathogens like HIV, herpes simplex, dengue virus, respiratory syncytial virus, and human cytomegalovirus. And, seaweed appears to contain other antiviral components that are enhanced by light (especially UVA) and not only protect our cells, but can directly inactivate the virus particles themselves. How cool is that?

What About Heavy Metal Toxicity?

As with any food that comes from the ocean, there’s some concern about seaweed accumulating heavy metals from polluted waters. Fortunately, a number of researchers and seaweed manufacturers have begun testing seaweed samples to ensure safety, and to identify any high-risk seaweed species!



The good news is, only one type of seaweed has consistently shown up as dangerous: hijiki, which frequently tests high for arsenic. Other types of seaweed (especially ones harvested or imported into the US) generally contain levels of heavy metals so low that even an extremely high seaweed intake would still be fine.

But, just to be safe, it’s smart to buy seaweeds from companies that perform regular testing on their products to ensure low levels of any dangerous contaminants.

What About the Mucilage?



As I wrote about in a previous post, seaweeds (and certain other foods like flaxseed and chia seeds) are high in a type of soluble fiber called mucilage. This fiber has legitimate health-boosting effects (especially for gut health), but can also stimulate the immune system (both Th1 and Th2, depending on the source of the mucilage)—making it potentially problematic for certain people with autoimmune conditions. And, because mucilage can be hydrolyzed into simple sugars like xylose, glucose, rhamnose, and galactose, pathogenic bacteria (like Clostridium difficile and Escherichia coli) can potentially thrive. For people who already have over-stimulated immune systems, the best bet is to avoid the highest-mucilage seaweeds (especially kombu and agar agar) and stick to varieties lower in mucilage, such as dulse. There are so many amazing benefits to seaweeds that they’re really not worth cutting out of our diets completely unless they’re clearly aggravating an existing health problem!

That All Sounds Great… But How Do We Eat The Stuff?!

So, how can we incorporate more of this amazing food into our diets? Here are some ideas!

Also, some components of seaweed (particularly fucoxanthin) require dietary fat to be best absorbed, so consuming seaweed in a meal with a fat-rich food (like avocado, olive oil, or sesame oil if you tolerate it) will enhance the nutritional perks!

All in all, seaweed is truly a powerhouse in terms of nutrition and health-promoting compounds. Enjoy this gift from the sea in whichever ways your taste buds prefer!


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Bernstein AM, et al. “A Meta-Analysis Shows That Docosahexaenoic Acid from Algal Oil Reduces Serum Triglycerides and Increases HDL-Cholesterol and LDL-Cholesterol in Persons without Coronary Heart Disease.” J. Nutr. 2012 Jan;142(1):99-104.

Damonte EB, et al. “Sulfated seaweed polysaccharides as antiviral agents.” Curr Med Chem. 2004 Sep;11(18):2399-419.

Heo SJ, et al. “Evaluation of anti-inflammatory effect of fucoxanthin isolated from brown algae in lipopolysaccharide-stimulated RAW 264.7 macrophages.” Food Chem Toxicol. 2010 Aug-Sep;48(8-9):2045-51.

Hwang YO, et al. “Total arsenic, mercury, lead, and cadmium contents in edible dried seaweed in Korea.” Food Addit Contam Part B Surveill. 2010;3(1):7-13.

Jensen GM, et al. “Effect of alginate supplementation on weight loss in obese subjects completing a 12-wk energy-restricted diet: a randomized controlled trial.” Am J Clin Nutr. 2012 Jul;96(1):5-13.

Kang SM, et al. “Molecular docking studies of a phlorotannin, dieckol isolated from Ecklonia cava with tyrosinase inhibitory activity.” Bioorg Med Chem. 2012 Jan 1; 20(1):311-6.

Konishi I, et al. “Halocynthiaxanthin and fucoxanthinol isolated from Halocynthia roretzi induce apoptosis in human leukemia, breast and colon cancer cells.” Comp Biochem Physiol C Toxicol Pharmacol. 2006 Jan-Feb;142(1-2):53-9.

Kotake-Nara E, et al. “Antiproliferative effect of neoxanthin and fucoxanthin on cultured cells.” Fish Sci. 2005;71:459–461.

Koyanagi S, et al. “Oversulfation of fucoidan enhances its anti-angiogenic and antitumor activities.” Biochem Pharmacol. 2003 Jan 15;65(2):173-9.

Liu JM, et al. “Inhibitory effect of fucoidan on the adhesion of adenocarcinoma cells to fibronectin.” Anticancer Res. 2005 May-Jun;25(3B):2129-33.

Maruyama H, et al. “The role of NK cells in antitumor activity of dietary fucoidan from Undaria pinnatifida sporophylls (Mekabu).” Planta Med. 2006 Dec; 72(15):1415-7.

Miao HQ, et al. “Inhibition of heparanase activity and tumor metastasis by laminarin sulfate and synthetic phosphorothioate oligodeoxynucleotides.” Int J Cancer. 1999 Oct 29;83(3):424-31.

Rose M, et al. “Arsenic in seaweed–forms, concentration and dietary exposure.” Food Chem Toxicol. 2007 Jul;45(7):1263-7.

Son EW, et al. “Antiviral and tumoricidal activities of alginate-stimulated macrophages are mediated by different mechanisms.” Arch Pharm Res. 2003 Nov;26(11):960-6.

Teas J, et al. “The consumption of seaweed as a protective factor in the etiology of breast cancer: proof of principle.” J Appl Phycol. 2013 Jun;25(3):771-779.

Wang H, et al. “Antiviral activities of extracts from Hong Kong seaweeds.” J Zhejiang Univ Sci B. 2008 Dec; 9(12): 969–976.



I read somewhere that seaweed is generally not so good for people with Hashimoto disease because of the high iodine content.

My kids love seaweed. We buy the nori snacks and they eat a couple packages a week. Bonus… perfect size to wrap stuff in. My 3 yr old loves wrapping olives, tuna, avocados, anything, in her nori. She likes the activity of it as much as the taste. My 18 month old loves it, too, though she’s less graceful at getting it all in.

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