Everything You Need to Know About Seaweed

Some 10,000 types of seaweed exist throughout the world, according to the Canadian Museum of Nature. With so many varieties, it’s no wonder that this sea vegetable has been used for more than a millennia. Ancient Chinese texts refer to this mineral-rich nutrient, noting, “There is no swelling that is not relieved by seaweed.”

Of the thousands of varieties of seaweed, about 300 to 400 are edible foods and for other commercial purposes. There are three main categories of seaweed: green, red, and brown. Seaweeds can be collected in the wild or farmed, and are used commercially in a variety of products, including personal care products, pet food, ice cream, fertilizers, cleaners, and dietary supplements. This seaweed resource lists many of the commercially available seaweeds and what they are used for.

With so many options, it can be overwhelming to know where to find seaweed, what the best varieties are, and how to use it. Here’s what you need to know to get the most out of seaweed.

What’s in Seaweed?

All seaweeds contain minerals, trace elements, vitamins, and amino acids. They’re excellent sources of calcium, iodine, and iron, and each type has its own specific nutrition profile as well, according to 150 Healthiest Foods on Earth by Jonny Bowden. No other group of plants contains more minerals and nutrients than seaweed. The bonus? Seaweed has about five calories per serving.

Like their terrestrial cousins, all seaweeds contain chlorophyll, which creates their green color. However, red and brown seaweeds also contain other pigments that diminish their green coloring. 

You may be most familiar with nori, a type of red seaweed used in sushi. Other varieties are gaining popularity, as the health benefits of seaweed become more widely known.

Of the varieties used in foods, there are five types of seaweed that are most commonly eaten today:

  • Arame: is a Japanese kelp that is typically dried, cut into thin strips, and added to soups and salads. Arame contains 100 to 500 times the amount of iodine found in shellfish, is high in iron and vitamin A, and has 10 times the calcium found in milk. Traditionally, arame is used in cooking in Japan, China, Korea, and Indonesia. It’s usually soaked before cooking, and can double in size when cooked.
  • Hijiki: has the highest calcium content of all seaweeds, with more than 10 times the calcium found in milk. Hijiki is also high in iron (about eight times the iron found in beef), magnesium, and vitamin A. Hijiki is available dried and is usually cooked to rehydrate before eating. It’s good in salads or stir-fried with other vegetables.
  • Kombu: is a member of the kelp family, and contains enzymes that help to break down the natural sugars found in beans, making them easier to digest. Try cooking beans with a piece of kombu to make it easier for the body to absorb the beans’ nutrients and less likely to cause gas. Kombu has 100 to 500 times the amount of iodine found in shellfish. Add a 2- to 4-inch strip of kombu to a pot of beans, soups, or brown rice.
  • Nori: is typically used as a sushi wrap and is very high in protein, with 100 grams of nori containing 30 to 50 grams of protein. Nori also contains high amounts of calcium, iron, potassium, vitamins E and K, and more vitamin A per serving than carrots.
  • Wakame: is another member of the kelp family. It’s also high in calcium—second only to Hijiki. It’s high in iron, protein, and other trace elements, and vitamins A, C, E, and K. Wakame is often used in salads.

Health Benefits of Seaweed

From an Ayurvedic perspective, seaweed is considered salty and warm, reducing both Vata and Kapha, according to Food As Medicine: The Theory and Practice of Food by Todd Caldecott.

Seaweed is known to detox the body and promote circulation, and is often used in cleansing drinks as well as topically as seaweed-detox body wraps, to help with skin tone, cellulite, and chronic dry skin, according to the Illustrated Encyclopedia of Healing Remedies by Dr. C Norman Shealy, M.D., PhD.

Seaweed has been shown to protect the body against radiation and environmental pollutants. And studies have shown that those who eat seaweed on a regular basis (such as people in Okinawa) have a significantly reduced risk of some cancers, including breast cancer.

Other benefits include:

  • Iodine found in kelp has been shown to boost metabolism and support the thyroid in cases of hypothyroidism.
  • Regular consumption of seaweed has been shown to improve bone health because of the high amounts of calcium and magnesium found in seaweed. Magnesium helps the body to absorb calcium.

How to Find Clean Seaweed

With so much concern over pollution and plastics in our oceans, how do you know if your seaweed is really clean and toxin free? Seaweed collected from more remote locations is more likely to be clean.

Two good sources are BC Kelp, a Canadian company that harvests wild seaweed in waters off the coast of British Columbia; and Maine Sea Vegetables, which sustainably harvests the product in the North Atlantic.

The Downside of Eating Seaweed

Most types of seaweed contain trace amounts of arsenic. Since hajiki contains the highest amounts of arsenic, you may consider limiting your intake of this sea vegetable.

And while many thyroid conditions can be helped by seaweed consumption, some thyroid conditions can be exacerbated by seaweed; be sure to check with your medical provider before eating seaweed if you have a thyroid condition.  

*Editor’s Note: The information in this article is intended for your educational use only; does not necessarily reflect the opinions of the Chopra Center's Mind-Body Medical Group; and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health providers with any questions you may have regarding a medical condition and before undertaking any diet, supplement, fitness, or other health program. 

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About the Author

Heidi Hackler

Holistic Health Coach and Health Writer
Heidi Hackler is a Certified Holistic Health Coach (CHHC) and blogger, who received her training from the Institute for Integrative Nutrition (IIN). She inspires healthy habits on her happiness and wellness blog , and through her holistic health coaching programs. Heidi quenches her thirst for knowledge through continuing education courses at Chopra Center Certifications, Dogwood School of Botanical Medicine, and Andrea Beaman’s New Healers Master Coaching program. Heidi lives with her husband and two kittens aboard their 40-foot sailboat. They have a zest for living the Happy Well...Read more