What Are the Health Benefits of Seaweed?

Here's how kelp and its cousins in the marine plant family can benefit your health and your taste buds.

Seaweed has long been a staple food of many Asian diets—particularly in Japanese cuisine. You may find seaweed most commonly in sushi, as well as salads, soups, and on their own as snacks.

"Seaweed is low-calorie, crunchy, salty, and super nutritious," said Carolyn Brown, RD, a nutritionist at Indigo Wellness Group in Conn. "The fact that it's plant-based and high in protein makes it on-trend, too."

Here's what you should know about seaweed nutrition, its health benefits, and how to incorporate it into your meals and snacks.

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Seaweed Nutrition

Seaweed, also known as algae, packs antioxidants—including vitamins A, C, and E—and is a great source of iodine. Per the Department of Agriculture, one cup (15 grams) of dried seaweed contains:

  • Calories: 44.7 calories
  • Protein: 4.77 grams
  • Fat: 0.601 grams
  • Carbohydrates: 7.86 grams
  • Fiber: 0.84 grams
  • Sugars: 0.456 grams
  • Vitamin A: 2.1 micrograms
  • Vitamin C: 0.75 milligrams
  • Vitamin E: 0.75 milligrams

However, the amounts of vitamins and minerals in seaweed vary slightly depending on the type of algae. There are different classes of algae—including:

  • Brown algae, like kelp, wakame, kombu, and arame
  • Red algae, like dulse and nori
  • Green algae, like sea lettuce
  • Blue-green algae, like spirulina and chlorella

Among those classes of algae, there are 100 types of edible seaweed. Some of the most popular types of seaweed include nori, kelp, wakame, and dulse.

Think of nori as the gateway seaweed. You can find it in sushi rolls and on sheets as "seaweed snacks." Kelp is the primary ingredient in dashi, a Japanese stock that forms the base of miso soup. Also, kelp noodles are a staple dish in Korean cuisine. You can even add kelp powder to smoothies.

Wakame is the main component of most seaweed salads and the wide, slippery seaweed you often find in miso soup. Usually sold dried, dulse is available whole, flaked, or powdered. Some people say it tastes like bacon when they fry dulse.

Health Benefits of Seaweed

"Seaweed is a vitamin and mineral jackpot, full of vitamins A and E, B vitamins, calcium, magnesium, potassium, copper, iron, and iodine," Brown said. It also contains omega-3s and polyphenols and is a good source of protein and fiber.

Here are a few ways that eating seaweed can have positive effects on your overall health.

Supports Thyroid Function

Per the Johns Hopkins Medicine Health Library, your thyroid gland, located in the neck, produces and releases thyroid hormone, which controls your metabolism.

One of the causes of hypothyroidism, or an underactive thyroid, is a lack of iodine. Hypothyroidism causes symptoms like gaining weight, feeling fatigued, and developing a goiter (a large growth on your neck and near your thyroid gland), among others.

So, adding seaweed to your diet is a great way to increase your intake of iodine if you have an underactive thyroid. In one study published in 2021 in the journal Food & Nutrition Research, researchers found that some types of seaweed can provide rich amounts of iodine.

However, it's important to proceed with caution while reviewing the iodine content of your seaweed. Too little or too high amounts of iodine can have adverse effects on your thyroid function.

Has Antioxidants That Prevent Chronic Diseases and Support Immunity

Vitamins A, C, and E, which are present in seaweed, are great sources of antioxidants.

Antioxidants are substances that help prevent cell damage, according to the National Library of Medicine, by decreasing the effects of free radicals. Free radicals are substances that contribute to chronic diseases, like cardiovascular diseases, diabetes, and certain types of cancer.

Also, antioxidants boost your immune system, allowing you to easily fight off the bacteria and viruses that make you sick.

Promotes a Healthy Gut

It turns out that your gut is an environment for a slew of "good" bacteria, also known as probiotics, that aid digestion and support your overall health. But whenever there are more "bad" bacteria that outweigh the probiotics in your gut, you may experience digestive issues.

Per the Johns Hopkins Medicine Health Library, fiber helps promote a healthy gut by increasing bowel regularity. And seaweed is a great source of fiber. In one study published in 2017 in the Journal of Applied Phycology, researchers reported that 23% to 64% of dried seaweed is fiber, which is higher than wheat bran.

Also, seaweed contains sulfated polysaccharides, which are sugars that influence the number of probiotics in your gut.

Helps Manage Weight

Adding seaweed to your diet may help you carefully manage your weight. Seaweed does not have many calories, and its high fiber content helps satiate your hunger.

Brown algae, which includes kelp, wakame, kombu, and arame, contain fucoxanthin. Fucoxanthin is a chemical that has antioxidant properties and also helps reduce your risk of obesity, per one study published in 2020 in the journal BBA Molecular and Cell Biology of Lipids.

Decreases Risk of Cardiovascular Disease

Seaweed may also help decrease your risk of developing cardiovascular disease, which is the most common cause of death in the United States.

One of the factors contributing to your risk of developing cardiovascular disease is high cholesterol. Per one study published in 2016 in the journal Marine Drugs, researchers explained that the vitamins and minerals found in seaweed, particularly fiber, can help reduce your cholesterol.

Keeps Blood Sugar Levels Stable

Among its antioxidant properties, fucoxanthin also helps regulate your blood sugar by decreasing the amount of sugar that your bloodstream absorbs.

So, brown algae that contain fucoxanthin can help decrease your risk of developing type 2 diabetes. Type 2 diabetes occurs when there is too much sugar in your bloodstream, according to the Johns Hopkins Medicine Health Library.

Risks of Eating Too Much Seaweed

Although seaweed has several health benefits, you want to make sure that you avoid eating too much of the tasty marine plant.

For instance, too much iodine can have negative effects on your thyroid. If you have hyperthyroidism, or an overactive thyroid, an abundance of iodine can aggravate your symptoms—including anxiety, fatigue, and irritability, among others, per the National Library of Medicine.

Also, some types of seaweed have a lot of heavy metals, like mercury, arsenic, and lead. If you're taking seaweed supplements, double-check the ingredients. The Food and Drug Administration does not regulate the amounts of those heavy metals in seaweed supplements.

How To Eat Seaweed (Besides Sushi)

Look for varieties of seaweed online or at Asian supermarkets, natural-food stores, and well-stocked grocery stores.

Most seaweed is sold, dried, consumed, or reconstituted in warm water. Some seaweed, like kelp, is also available frozen, which means it doesn't need to be reconstituted.

Executive chef Jeremy Rock Smith, a faculty member at the Kripalu Center for Yoga & Health in Stockbridge, Mass., recommended:

  • Adding kombu when preparing dried beans
  • Sneaking kelp into slaws for a great depth of flavor
  • Shaking store-bought furikake (a topping that includes sesame seeds and nori) onto popcorn, roasted vegetables, cooked fish, or omelets

You can also snack on nori and dulse right out of the bag, whip up a seaweed salad with sesame oil and garlic, and add seaweed to chicken bone broth. But no matter how you add seaweed to your meals and snacks, you will be supporting your overall health.

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