Have you observed those green paper wraps on your favorite sushi rolls? These wraps are seaweed, also known as macroalgae. They are edible. The benefits of seaweed are many, and you can find it along the rocky shorelines of the sea. It is highly nutritious and is considered a superfood for its health benefits. Seaweed is also an important food source for marine life and is available in different colors like green, red, and brown. This article explores the nutrition profile of seaweed, types, health benefits, and possible adverse effects. Keep reading to know more.
In This Article
Seaweed formed an important part of the diet for coastal people in ancient times. Today, more than 145 varieties are used around the world. Most of the edible seaweed varieties differ in color coming from different species. As per their coloring pigment, they are broadly classified as brown algae (Phaeophyceae), red algae (Rhodophyta), and green algae (Chlorophyta).
- Nori, or purple laver, is the common dark-colored seaweed used in sushi preparations. With its high protein and nutrient content, it is one of the most nutritious types of seaweed.
- Aonori, or green laver, commonly known as “sea lettuce” is widely cultivated in Japan.
- Dulse is a type of red algae with leathery fronds.
- Haidai (in China) and Kombu (in Japan) are other types of dried seaweed.
- Other edible seaweed varieties include winged kelp, sea grapes, Irish moss, hiziki, and mozuku.
While seaweeds grow in oceans all over the world, they’re most commonly used in Asian cuisines, in sushi, miso soup, salads, and stews.
Let’s have a look at the nutrition details below.
Seaweed Nutrition Facts
According to the USDA, 2 tablespoons (10g) of seaweed (wakame variety) provides us with the following nutrients (1).
- Calories: 4.5
- Fat: 0g
- Sodium: 87.2mg
- Carbohydrates: 0.9g
- Fiber: 0g
- Sugars: 0g
- Protein: 0.3g
- Magnesium: 10.7mg
- Calcium: 15mg
- Iron: 0.2mg
Seaweed is rich in nutrition and low in calories. It is an important source of nutrients such as iodine, vitamin B12, and vitamin D, iron, calcium, folate, and magnesium.
Going further, let’s explore the many health benefits of seaweed, the superfood.
Health Benefits Of Eating Seaweed
Seaweed contains unique plant compounds that might help prevent a number of diseases and promote good health.
- May Protect Against Asthma
Since asthma is an inflammatory disease closely related to diet and environmental factors, the dietary intake of polyunsaturated fats and vitamins found in seaweed seems to help in lowering the development of asthma. Higher intakes of seaweed and seafood have been associated with lower risks of asthma. Research on similar lines found a 34% reduction in the prevalence of doctor-diagnosed asthma on the dietary intake of seaweeds. Though more research is warranted, introducing seaweed early in pregnancy and childhood appears to be beneficial in preventing asthma (2).
- May Reduce Risk Of Osteoporosis
Seaweed contains antioxidant compounds called fucoidans which are indicative of protecting the bone-building cells, osteoblasts (3). This may help prevent bone damage and osteoporosis. A seaweed diet is also enriched with calcium and vitamin K, two key nutrients for bone strength (4).
- May Promote Heart Health
Inflammation, high cholesterol, oxidative stress, and high blood pressure are all potential symptoms of cardiovascular health concerns. Seaweed is rich in soluble fiber, antioxidants, and vital minerals that help alleviate these concerns and improve your heart health (5). Soluble fiber is known to bind to and help remove bad cholesterol from the body (6). Seaweed, especially kombu and dulse, are rich sources of soluble fiber (7), (8). In one study, rats with high cholesterol were given a high-fat diet supplemented with 10% freeze-dried seaweed. The results showed 40% lower total cholesterol, 36% lower LDL cholesterol, and 31% lower triglyceride levels (9). Additionally, the potassium in seaweed can also help lower blood pressure (5).
- May Help Proper Thyroid Functioning
Seaweed is rich in iodine that supports the proper functioning of the thyroid gland. The thyroid gland relies on iodine to make hormones. Seaweed can absorb highly concentrated amounts of iodine from the ocean water (10).
Without enough iodine, your body suffers from a condition called hypothyroidism with symptoms like fatigue, sudden weight changes, and swelling of the neck over time (11). The recommended dietary intake (RDI) for iodine is 150 mcg per day (12). Just one teaspoon (3.5 grams) of dried kelp could contain 59 times the RDI (13).
The average iodine content of three other dried seaweed varieties is as below (13):
- Nori: 37 mcg per gram (25% of the RDI)
- Wakame: 139 mcg per gram (93% of the RDI)
- Kombu: 2523 mcg per gram (1,682% of the RDI)
Along with iodine, the amino acid called tyrosine found in seaweeds also helps the thyroid gland function properly (14).
- Rich In Antioxidants
In addition to containing the antioxidant vitamins A, C, and E, seaweed contains a wide variety of beneficial plant compounds like carotenoids and flavonoids. These are known to protect our body from the effects of toxic free radicals (15), (16).
Fucoxanthin, the main carotenoid found in brown algae such as wakame, has 13.5 times the antioxidant capacity of vitamin E (15). It has been shown to protect cell membranes better than vitamin A (17). Seaweed is rich in a few other plant compounds with antioxidative properties as well (18).
- May Help Improve Blood Sugar Levels
As per a study conducted on Japanese people, fucoxanthin, a carotenoid found in brown seaweed, might help improve blood sugar control (19). Participants were given a local seaweed oil containing either 0 mg, 1 mg, or 2 mg of fucoxanthin. Those who received 2 mg of fucoxanthin were reported to have improved blood sugar levels, compared to the group who had received 0 mg (19). The study also noted additional improvements in blood sugar levels in those who are genetically predisposed to insulin resistance usually associated with type-2 diabetes.
Additionally, the fiber alginate in seaweeds was found instrumental in preventing spikes of blood sugar levels in animals after being fed a high-sugar meal. Studies suggest that alginate may help reduce the absorption of sugar into the bloodstream (20), (21).
- Seaweed Might Help In Weight Loss
Seaweed varieties contain a good amount of fiber that helps you feel full and delay your hunger pangs, thereby making you eat less (22). A 5g serving of brown, red, or green seaweed has been found to contribute up to 14.28%, 10.64%, or 12.10% of dietary fiber intake, respectively (23). Seaweed is also known to have anti-obesity effects. As per a few animal studies, compounds like alginate and fucoxanthin found in seaweed might also have fat-reducing effects (24), (25). Although these studies’ results seem promising, further research on humans is warranted to establish the findings.
Going further, let’s see how you can include seaweed in your diet to reap its many benefits.
How To Include Seaweed In Your Diet
Seaweed can be used fresh or as dried flakes. Let’s explore the different ways you can add seaweed into your diet:
- Make onigiri from rice and dried seaweed nori wrappers.
- Add it to your soups and salads.
- Add kombu to cooked beans.
- Make different varieties of homemade sushi.
- Mix fresh arame and wakame with vinegar, sesame oil, scallions, and garlic for a seaweed salad.
- Make a vegan salad with chickpeas, vegan mayonnaise, celery, red onion, salt, pepper, and dulse flakes.
- Top meals with a mix of ground nori, kombu, dulse, salt, black pepper, and sesame seeds.
- Make a soup broth with dried kelp or kombu.
Having said that, do you know when and how you can source seaweed? Let’s explore that in the next section.
Best Time To Consume Seaweed
Seaweeds meant for human consumption were usually collected fresh from the seashore or picked in the sea. They were harvested locally and eaten fresh within a short span of time.
Soon people realized that seaweeds can be dried, transported easily, and stored for a longer time in dried form. This makes them readily available all through the year. So in case, you can’t get fresh seaweed in your region, you can most likely get your hands on some variety of dried seaweed in a nearby Asian grocery store. Seaweed farming or cultivation is also being widely practiced all over the world to meet its rising demand and popularity.
Having said that, let’s have a look at some of the potential drawbacks of seaweed.
Side Effects And Drawbacks Of Seaweed
Eating fresh seaweed as such is considered safe for most people. While the plant offers many health benefits as seen above, there are a few things to keep in mind before having seaweed.
Seaweed is a natural source of vitamin K, which might interfere with the anticoagulant effects of blood-thinning medicines like Coumadin (warfarin) (26). If you take seaweed or foods high in vitamin K regularly you should inform your doctor to help determine the right dosage of such medication (27).
Depending on the source of seaweed, it might contain high levels of heavy metals like mercury, lead, cadmium, and arsenic. Alternating between the types of seaweed and limiting your intake frequency might help you reduce heavy metal exposure from seaweed (28).
Now let’s look into how you should store seaweed and the safety precautions you can take.
Storage And Food Safety
- Fresh seaweed like other leafy greens should be washed and cleaned under running water before consumption or further preparation. It can then be used directly or stored in the fridge for later use.
- Packaged dried seaweed, once opened, should be kept sealed or stored in an airtight container. Look for the “use by” date mentioned on the package and preferably get branded products to avoid any heavy metal toxicity.
To Sum Up
Though more commonly used in Asian countries, seaweed benefits are gaining popularity all over the world. It is one of the best dietary sources of iodine. It also contains important vitamins and minerals such as B vitamins, vitamin K, zinc, and iron along with antioxidants that help protect your cells from damage. However, too much iodine or vitamin K can be harmful to your thyroid and kidney health respectively. You can safely enjoy the benefits and flavor of seaweed when taken in regular but small amounts.
Expert’s Answers For Readers’ Questions
Can I eat seaweed every day?
Yes, seaweed can be had every day but in small amounts. A daily intake of 5-10g gives you enough iodine and potassium for the day.
Is seaweed good for skin?
Yes, the bioactive compounds in seaweed are being widely used for many cosmetic skincare formulations. These usually help your skin get rid of hyperpigmentation, acne, and premature signs of aging (29).
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- Asthma and Dietary Intake of ‘Fish’ ‘Seaweeds’ and Fatty Acids in Korean Adults
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- The Effects of Marine Algae on Osteoporosis
- Seaweeds as Preventive Agents for Cardiovascular Diseases: From Nutrients to Functional Foods
- Fiber and cardiovascular disease risk: how strong is the evidence?
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- Seaweed extracts and unsaturated fatty acid constituents from the green alga Ulva lactuca as activators of the cytoprotective Nrf2–ARE pathway
- Reduction of HbA1c levels by fucoxanthin-enriched akamoku oil possibly involves the thrifty allele of uncoupling protein 1 (UCP1): a randomised controlled trial in normal-weight and obese Japanese adults
- Non-starch polysaccharides extracted from seaweed can modulate intestinal absorption of glucose and insulin response in the pig
- Effects of soluble sodium alginate on cholesterol excretion and glucose tolerance in rats
- Emergent Sources of Prebiotics: Seaweeds and Microalgae
- Risks and benefits of consuming edible seaweeds
- Laminaria japonica as a food for the prevention of obesity and diabetes
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- Metals in edible seaweed
- Potential Use of Seaweed Bioactive Compounds in Skincare—A Review