Seaweed benefits for Thyroid, digestion, heart health, Diabetes, and more

By: Cat Ebeling
Co-author of the best-sellers:  The Fat Burning KitchenThe Top 101 Foods that Fight Aging & The Diabetes Fix

We’ve probably all noshed on Nori, the seaweed wrapper on sushi, and perhaps tried a seaweed salad or two. But for us Westerners, seaweed doesn’t get the star billing it should as a superfood—and trust me, seaweed is most definitely a superfood! A staple in Asian foods for years, it’s time for us to recognize the incredible value of seaweed.

While there are a variety of edible seaweeds to choose from, in general they all are very high in iodine, sodium, calcium, magnesium, phosphorus, iron, vitamin K, folate, copper and powerful antioxidants. In fact, seaweed generally has about 10 times the minerals of conventional plants. Dried algae contains some of the most concentrated nutrients, while spirulina and chlorella are high in protein, with all the essential amino acids needed. Seaweed contains a rich and vast source of antioxidants and phytochemicals.

Seaweed’s pool of antioxidants prevent inflammation, powerful natural weapons which in turn help to prevent cancer, arthritis, celiac disease, asthma, depression, Alzheimer’s, type 2 diabetes, and heart disease and more.

Some of the more common edible seaweed types are kelp, wakame, sea lettuce, kombu, arame,  nori, dulse, chlorella, agar, carrageenan, and duckweed. Seaweed is known for its massive amount of iodine, which is good for the thyroid gland (but if you have hyperthyroid, then you need to be careful with too much iodine.)  Not only does the thyroid help keep your metabolism burning at a good rate, it also helps your hair, skin and nails grow.

Thyroid Health and Metabolism

Iodine helps the body to produce thryoxine and triiodothyronine, two of the most important thyroid hormones. Iodine and thyroid hormone are also very vital to the central nervous systems of newborns, so balanced iodine levels are extremely important for baby’s brain cells and nervous system. Mild iodine deficiency is very common, given the low levels of iodine in most of our foods. Mild iodine deficiency can lead to hypo, or low thyroid issues, such as weight gain, fatigue, and depression. It is important, however, to understand that too much of a good thing—in this case, iodine—can also cause issues with thyroid hormone. The recommended amount of iodine is usually about 150 mcg per day.

Depending on where your seaweed came from and what type it is, it may contain more or less iodine than others. Kelp and other brown seaweeds contain more iodine than the green forms. Kombu, contains 100-1,000 times the iodine that nori does.

To learn more about Thyroid health, here’s a great article: The Ultimate Guide to Thyroid Health

Defends Against Diabetes

Seaweed contains compounds which have been found to help stabilized blood sugar levels. Brown algae contains a compound called fucoxanthin, which helps to fight obesity, reduce insulin resistance, and maintain a healthy blood sugar level. Seaweed also contains a different type of fiber which helps to slow down the rate that carbohydrates are absorbed after eating, which in turn slows down the rate at which the those carbs affect blood sugar. In one study, a group on a powdered seaweed supplement reported a 12% decrease in blood sugar levels, as well as a slight reduction in their hemoglobin A1C levels. Hemoglobin A1C is a measure of blood sugar levels over a period of 2-3 months. More research is needed in this area of disease prevention, however, related to the amount and types of seaweed for optimal health and diabetes prevention.

Fights Cancer, Balances Hormones

Another great thing about seaweed is that it can help to regulate estrogen and estradiol (a form of estrogen) levels in the body. Regulating estrogen helps to prevent breast cancer. It is even thought that the Japanese, who eat a lot of seaweed, also suffer less from breast cancer and other female hormone-related issues. Seaweed is also thought to help ease PMS, and improve female fertility issues as well.

The unique soluble fiber in seaweed helps to prevent colon cancer, and other compounds, found in kelp, wakame, and kombu, help to prevent the cancer cells from spreading and multiplying.

Heart health

Seaweed is actually very good for heart and blood vessel health. The powerful antioxidants in seaweed help to reduce blood pressure, prevent blood clots, and reduce inflammation. Seaweed also helps to reduce LDL, triglycerides and total cholesterol levels in those who eat it on a regular basis. Several studies show that an adequate seaweed intake may reduce blood pressure levels in children, adults and elderly people.

Healthy Immune Function

Seaweed is a powerful boost to your immune system because of the marine plant compounds that power up your immune system, calm your allergies, and fight pathogens that cause disease.  The marine plant polysaccharides exert a strong anti-viral effect on the body, killing off viruses that cause infections in humans. Studies show that these compounds are especially effective against human viruses like herpes and HIV.

Healthy Gut

Seaweed contains a variety of substances like agars, carageenans, and fucoidans which work in the gut as prebiotics, creating food and nutrition to feed the healthy bacteria in the gut. In addition, the rich soluble fiber helps to ensure smooth digestion and regular bowel movements. In turn, healthy bacteria in the gut produce a compound called butyrate, which has anti-inflammatory effects in the digestive system, helping to decrease inflammation and fighting colon cancer as well.

Be Careful of Too Much of a Good Thing

In very large quantities, seaweed’s abundance of iodine could create troubles with the thyroid, potentially causing hyperthyroid conditions or actually contributing to thyroid cancer (however it should be noted that this would be very rare, and only be a risk from eating very large quantities of seaweed for long periods of time).  One or two tablespoon servings of brown seaweed a week will give you enough of its healthy benefits without any health problems. Nori (the kind of seaweed on your sushi roll), has a lower iodine content, so you’d have to eat a lot of sushi for it to cause any problems.

Seaweed can also carry its share of toxins, arsenic, and other heavy metals and even potentially radiation from nuclear waste from the Fukushima meltdown depending on the area it was harvested.  Heavy metals can also accumulate in marine plants over time, creating dangerously high levels of toxins like the arsenic found in hijiki. The best and safest choices are certified organically grown seaweed, such as Maine Coast or Eden Foods brands.

What do you do with seaweed? I love buying toasted Nori and using it for wraps. You can add in some tuna salad, a few sprouts and a slice of avocado and you have a nutrition packed, low carb lunch. Or wrap around a bunch of veggies, scrambled eggs or hummus—or throw a bit into your smoothie!  Sprinkle dulse on salads and soups, use kelp as a replacement for salt in cooked dishes or add a strip or two of kombu to your beans and they will come out perfectly.  We get some kelp granules that we sprinkle into soups, scrambled eggs, or even tomato sauces.

Seaweed is a superfood and is worth adding to your list of favorites. Just don’t overdo it! Enjoy!

English, Nick. The Green Superfood you are not
Eating but Should Be. Huffington Post. (2013). Retrieved from
English, Nick. Superfood: Seaweed. Retrieved from
Petre, Alina, MS, RD. Why Seaweed is Super Healthy and Nutritious. Retrieved from

About The Watchdog

Mike Geary has been a Certified Nutrition Specialist and Certified Personal Trainer for over 15 years now. He has been studying nutrition and exercise for almost 25 years, ever since being a young teenager. Mike is originally from Pennsylvania, but has fallen in love with mountain life and now resides in the picturesque mountains of Utah. Mike is an avid adventurist and when he’s not spending his time skiing, mountain biking, hiking, or paddleboarding on the lake, he has enjoyed skydiving, whitewater rafting, piloting an Italian fighter plane (seriously), scuba diving, heli-skiing, and traveling all around the world, enjoying learning about different cultures. At the age of 40, Mike now feels healthier, stronger, and more energetic than when he was 20... All because of a healthy lifestyle and great nutrition!

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  1. This article sbout seaweed is all great but there is a risk of seaweed harvested from Japanese waters which may be radioactive and very harmful especially for our thyroids.
    A warning to buyers to check where the product is from is imperative.
    Thanks for your great articles.

  2. I agree that seaweed WAS ONCE UPON A TIME a superfood. But I’m not sure I could ever eat it again knowing how polluted and toxic our oceans have become. I’ve also been avoiding seafood for the same reason.

    Fukushima radiation has contaminated the entire Pacific Ocean, it’s being called an EXTINCTION LEVEL EVENT.

  3. I own Ocean Harvest Sea Vegetable Company in Mendocino California. I appreciate your article, but when you recommend seaweed brands, please know that Ocean Harvest is the only seaweed company on the west coast to test our seaweeds for radiation and heavy metals, and we have found NO radiation from Fukushima since 2011. I wish you would do your homework before scaring people off seaweeds on the west coast! Also, there are no “organic” seaweeds. The only thing to be certified organic is the drying and storage process. All seaweeds grow wild.
    You can find our seaweeds at
    Thank you,
    Terry d’Selkie

  4. Should we be cautious of anything from the sea because of fukushima. millions of gallons of nuclear waste everyday.

  5. Ebeling, If the seaweed is from without polluted and toxic oceans so it would be the best choice. Otherwise, not a perfect choice. By the way, it can boost your immune system as fast as possible. I read many journals where has the proof. Ebeling, can you write a post that how we choose toxin free seaweed?

    • I’ve been diagnosed with Systemic Scleroderma. Look it up, it’s the 4th worst disease to have in the world. Spirulina keeps my gut healthy as it’s one of the things to shut dpwn with this disease. It keeps me regular and feeling normal as I’ve experienced when my gut has been on the path to shutting down – Dpirulina sorts it ourmt and now I always remember to take a little every day with Braggs cider vinegar and herbal teas. Naturally, I’m on board all the other healthy stuff being immumosuppressed but so far doing amasingly. 95% of SSc sufferers have severe heart, lung, osophageal, kidney, muscle, nerve etc problems so I can safely speak with great authority that these algae and other superfoods work – and a 180 turn around healthy diet. If you saw me you’d think nothing was wrong with me and how healthy I look. They definitely work!

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