Seaweed Health Benefits, Nutrition, Uses & Side Effects

by Meenakshi Nagdeve last updated -

Seaweed has earned the superfood status in recent times all over the world. It is notably the most prominent part of Asian diets for the longest time, particularly in Japan, Korea, and China. There are about 10,000 species of seaweed reflecting its beneficial diversity, in flavor and nutritional properties.

Coming to health benefits, seaweed has a plethora of them! These include the ability to manage obesity, diabetes, influenza, and radiation poisoning. It helps in improving digestive health, dental health, cardiovascular health, and maintaining healthy skin and hair. It protects eyes and has anti-coagulant properties. It also covers the body’s need for iodine and helps in detoxification.

What is Seaweed?

Seaweed is a general nomenclature used for a number of species of algae and marine plants that breed in varied water bodies like rivers and oceans. They grow in a wide range of sizes from minuscule to gigantic. Most of the seaweeds are medium-sized and are available in multiple colors like red, brown, and green. They can be spotted ubiquitously on the seashores or coastlines. [1]

Microscopic seaweed like phytoplankton grows hanging in the water. Bigger ones like giant kelp, which is one of the largest plants in the world, grow enormously and stand like an underwater tree with its roots at the foot of the sea. Unlike a weed that grows liberally and can be harmful to the area it dwells in, it plays an extremely vital role in marine life.

A bowl of stir-fried wakame seaweed on a wooden mat

Seaweed is a staple ingredient in South-east Asian countries. Photo Credit: Shutterstock

Nutrition Facts

Seaweed, agar, raw
Serving Size :
Water [g]91.32
Energy 26
Energy [kJ]109
Protein [g]0.54
Total lipid (fat) [g]0.03
Ash [g]1.36
Carbohydrate, by difference [g]6.75
Fiber, total dietary [g]0.5
Sugars, total including NLEA [g]0.28
Calcium, Ca [mg]54
Iron, Fe [mg]1.86
Magnesium, Mg [mg]67
Phosphorus, P [mg]5
Potassium, K [mg]226
Sodium, Na [mg]9
Zinc, Zn [mg]0.58
Copper, Cu [mg]0.06
Manganese, Mn [mg]0.37
Selenium, Se [µg]0.7
Thiamin [mg]0.01
Riboflavin [mg]0.02
Niacin [mg]0.06
Pantothenic acid [mg]0.3
Vitamin B-6 [mg]0.03
Folate, total [µg]85
Folate, food [µg]85
Folate, DFE [µg]85
Choline, total [mg]6
Vitamin E (alpha-tocopherol) [mg]0.87
Vitamin K (phylloquinone) [µg]2.3
Fatty acids, total saturated [g]0.01
16:0 [g]0.01
Fatty acids, total monounsaturated [g]0
16:1 [g]0
18:1 [g]0
20:1 [g]0
Fatty acids, total polyunsaturated [g]0.01
20:4 [g]0
20:5 n-3 (EPA) [g]0.01
Sources include : USDA [2]

Nutritional Value of Seaweed

Seaweed contains a massive variety of health-promoting components as compared to the majority of other plant and animal-based foods available on land. It has a rich source of essential minerals such as magnesium, calcium, copper, potassium, selenium, zinc, iodine, and iron. It is a treasure trove of antioxidants, phytonutrients and rich fiber content that is required by the body. It also contains omega-3 fatty acids and all the vital amino acids necessary for the body. [3] [4] [5]

Health Benefits of Seaweed

Seaweed offers many health benefits that are famous for a while now. Let us have a look. [6]

Source of Iodine

Seaweed is a rich source of iodine, which it absorbs in ample amounts from the seawater. Iodine is a vital nutrient required for proper growth for all age groups. Iodine is extremely crucial in pregnancy and breastfeeding for the normal development of the brain cells of the baby. Deficiency during these periods or early childhood can lead to weak intellectual growth and abnormal development of the brain. [7]

Prevents Obesity

Scientific research has shown that edible seaweed possesses anti-obesity effects. The compound fucoxanthin present in it helps in reducing the accumulation of fats and aids in weight loss. Due to its ability to promote the oxidation of fats, it is used in making prescription diet pills and gastric banding pills. These pills should always be considered after consultation with a medical professional. [8]

Aids in Digestion

Seaweed has a mild laxative effect and is quite useful in maintaining healthy digestion. It aids in stimulating the release of digestive enzymes, supporting the absorption of nutrients, and facilitating the metabolism of fats. Studies have shown that polysaccharides exert prebiotic effects on the gut, which helps in the normal functioning of beneficial stomach bacteria and shields the stomach wall against harmful bacteria. [9] [10] [11] [12]


The fucoxanthin compound present in brown algae has been proven effective in exerting anti-diabetic effects. Along with this, the triglyceride absorption of seaweed Laminaria japonica, also known as kombu, has been praised for its effect on type-2 diabetes. According to one research, the anti-diabetic effect can be attributed to the presence of alginic acid in the seaweed kombu. [13] [14] [15]

Dental Care

Seaweed extracts have long been appreciated for their preventative effect in the growth of dental cavities. The anti-inflammatory properties are responsible for the improvement in the functioning of salivary glands and making the oral tissues more resistant to damage. Alginate, a salt of alginic acid extracted from seaweed, is quite useful in the fabrication of dental molds and teeth whitening. [16] [17]

Protects Heart Health

Seaweed has been useful in sustaining lower levels of triglycerides and cholesterol in the body. This helps in maintaining a healthy heart, increasing circulation in the blood vessels, and preventing fatal conditions like heart failure, atherosclerosis, and peripheral artery ailments. [18] [19] [20]

Skin Care

The wealth of essential vitamins, minerals, amino acids, and antioxidants in seaweed helps in keeping the skin revitalized, moisturized, and youthful. These elements guard the skin against the harmful effects of environmental pollutants and help slow down the skin’s aging process. Scientific research has made it evident that seaweed extracts contain anti-aging properties and are a useful ingredient in the manufacturing of skincare cosmetics. [21]

Other Benefits

Seaweed helps in maintaining the electrolyte balance of the body. The anti-inflammatory effect has proven effective in the treatment of osteoporosis and rheumatoid arthritis as well. They possess healing properties that aid in enriched blood circulation and a robust immune system. [22] [23]

Uses of Seaweed

Culinary Uses

Seaweeds have a nice flavor and is served as a delicacy in many Asian countries such as Japan, China, and Korea. Nori, kombu, and wakame are some of the most commonly grown and used species in these countries. Famous Japanese sushi roll uses seaweed called nori as an ingredient in rice and raw fish.

Plant Growth: Seaweed also provides a range of benefits favorable for the growth of plants. They aid in the formation of roots, provide better resistance, and enhance the yield and shelf life of harvested crops. They are used in the manufacturing of fertilizers and soil conditioners. [24]

Wastewater Treatment: Seaweed can also be utilized in the treatment of wastewater. They have been quite effective in the treatment of agricultural waste and sewage to lower the toxic content of water such as nitrogen and phosphorous before the water reaches the rivers or lakes. They also help get rid of the toxic metals from the waste released by those industries.

Side Effects of Seaweed

Excess Iodine: The consumption of excess seaweed may increase the quantity of iodine above acceptable levels. This can raise the levels of thyroid-stimulating hormone, which can cause serious conditions like thyroid and goiter. These conditions can heighten the risk of thyroid cancer. [25]

As per the guidelines set by the Food and Nutrition Board, the daily requirement of iodine for adults is 150 mcg per day and the tolerable upper limit is 1100 mcg/day. For infants and other younger groups, it is proportionately lower. [26]

Heavy Metals and Other Chemicals: Seaweed also contains some concentration of heavy metals and chemicals like mercury, cadmium, lead, and arsenic which can be poisonous. Significant consumption of these heavy metals present in it can lead to medical complications like cancer, brain damage, gastrointestinal problems, and kidney diseases. [27] [28]

Pregnancy and Lactation: The surgical application of extracts of the seaweed Laminaria during childbirth is not considered safe. Laminaria alters the hormones and may result in fatal infections or other serious conditions in both mothers and babies.

Drug Interaction: Seaweed can interact with certain drugs like anti-thyroid and anticoagulants, which may lead to various medical complications. The intake of iodine while undergoing treatment for an overactive thyroid can lead to abnormal functioning of the thyroid gland. [29] Protection Status
About the Author

Meenakshi Nagdeve, Co-Founder, Organic Facts is a health and wellness enthusiast and is responsible for managing it. She has completed the Nutrition And Healthy Living Cornell Certificate Program, Cornell University, US. She holds a Post Graduate Diploma in Management from IIM Bangalore and B. Tech in Metallurgical Engineering and Materials Science from IIT Bombay. Prior to this, she worked for a few years in IT and Financial services. An ardent follower of naturopathy, she believes in healing with foods. In her free time, she loves to travel and taste different types of teas.

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