Seaweeds and Their Health Benefits

By Irina Bright

This article is part of our Health & Foods section

It is really hard to overestimate the importance of seaweeds (or sea vegetables) and their benefits for our health.


brown seaweed Photo: Rosie Steggles


Types of Seaweeds

Seaweed Nutrition

Seaweed Health Benefits

      Sulfated Polysaccharides
      Other Seaweed Compounds
      Health Benefits for Cancer
      Health Benefits for Cardiovascular Disease, Obesity & Diabetes
      Health Benefits for Thyroid Disorders
      Health Benefits for Liver & Kidney Disease
      Health Benefits for Neurological Disorders
      Health Benefits for Infections

Seaweed Benefits for Skin & Bones

Seaweed Benefits for Weight Loss

Other Interesting Points

Seaweeds for Tiredness & Chronic Fatigue Syndrome

Seaweeds or Sea Salt?




Indeed, humans had consumed seaweeds & other types of seafood for millennia. The Aquatic Ape hypothesis introduced by some scientists in the 20th century, asserts that the human race itself may have originated from semi-aquatic pre-historic creatures who lived mostly along coastal areas of our planet.

This leads us to conclude that we may depend on sea-based nutrition a lot more than we used to believe.

Seaweeds are widely considered to be functional foods - the ones that can deliver health benefits much deeper than simple staple foods that most of us consume every day.

If we look at their nutritional value, seaweeds stand out, first & foremost, as being an excellent source of:

  • unique marine polysaccharides which are believed to have numerous health-boosting properties (working in harmony with other compounds present in seaweeds), and
  • many unique marine minerals & trace elements that are rarely found (or found in small amounts) in terrestrial plants.

But seaweeds offer a lot more nutrition-wise than that. They are the ultimate marine superfood. Many renowned nutritionists recommend incorporating seaweeds into our diets.

Types of Seaweeds

So what types of seaweeds do we know about?

There are, of course, hundreds of different species of edible seaweeds living in oceans & seas across the world. Inevitably, the species that grow along coastal areas - rather than in deep waters - are the most popular ones, for purposes of human consumption.

As science gains more knowledge about life on Earth - and all the creatures that inhabit it, we still don't know much about what's happening deep down in the oceans. It will be a fair assumption to say that there could be thousands more species of edible seaweeds that we could use as foods.

For now, here is what we know.

Edible seaweeds can be generally divided into the following categories (Ref. 1):

  • brown seaweeds (phaeophyta),
  • red seaweeds (rhodophyta), and
  • green seaweeds (chlorophyta).

As you can see, this classification is based on pigments that are found in each category:

The presence of these different phytopigments in algae is related to their sea habitat because not all macroalgae need the same light intensity to perform photosynthesis. Thus, green macroalgae, which are able to absorb large amounts of light energy, abound in coastal waters, while red and brown macroalgae prevail at greater depths where penetration of sunlight is limited. (Ref. 1)

Some of the most widely-consumed species of seaweeds, especially in Asia, are: kombu (Laminaria japonica); wakame (Undaria pinnatifida); nori (Porphyra species); dulse (Palmaria palmata); sea grapes (Caulerpa lentillifera).

Seaweeds (all their 3 types) are also collectively known as macro-algae.

As more international consumers become aware of seaweeds' medicinal properties, and the fact that they can actually be a very tasty food, their popularity is now spreading from Asia to many other parts of the world.

Let's take a closer look at seaweed nutrition.

Seaweed Nutrition

We start our discussion of seaweeds' nutritional profile from their various bioactive components which, many experts believe, are primarily responsible for seaweeds' healing properties.


brown seaweed © Rhys Asplundh

Polysaccharides (often called sulfated polysaccharides) found in marine plants possess many physiological and biological properties which make seaweeds such a valuable *health food*. (Ref. 2)

Here is a simple breakdown of polysaccharide contents, by type of seaweeds (Ref. 3):

1) Brown seaweeds (phaeophyta) - Fucus, Sargassum, Laminaria, Undaria, Dictyota, Dictyopteris, Ascophyllum, Lobophota, Turbinaria etc - contain the following polysaccharides:

  • alginates, aka alginic acid or algin (composed of mannuronic acid and guluronic acid),
  • fucans/fucoidans (branched polysaccharide sulfate esters, with L-fucose building blocks),
  • laminarins (glucans composed of glucopyranose residues).

2) Red seaweeds (rhodophyta) - Gracialaria, Gigartina, Gelidium, Lomentaria, Champia, Solieria, Gyrodinium, Nemalion, Sphaerococcus etc - contain the following polysaccharides (most of which are galactans):

  • agars (linear polymers composed of agarose (gelling fraction) and agaropectin (non-gelling fraction)),
  • carrageenans (classified into kappa (strong gels), iota (soft gels) and lambda (thickening polymers)),
  • other polysaccharides (xylans, xylogalactans, hypneans, porphyrans, funorans).

3) Green seaweeds (chlorophyta) - Ulva, Enteromorpha, Monostroma, Caulerpa etc - contain the following highly complex sulfated hetero-polysaccharides:

  • sulfate & uronic acids (composed of glucuronic acid, rhamnose, arabinose and galactose),
  • ulvans (composed of xyloglucan, glucuronan and cellulose).

Polysaccharides function as very efficient prebiotics in the intestinal tract of our systems. We discuss polysaccharides' health benefits as prebiotics in one of the sections below.

Pigments & Polyphenols

Pigments (colours) and polyphenols are major chemical constituents of all macro-algae. They are believed to offer a wealth of biological properties which, among other components, make seaweeds such a valuable source of food.

Carotenoids and chlorophylls are the main seaweed pigments. (Ref. 1)

Fucoxanthin, β-carotene, antheraxanthin, lutein, neoxanthin, violaxanthin & zeaxanthin are notable carotenoids found in many species of seaweeds. (Ref. 1)

Fucoxanthin is a very powerful carotenoid found in brown seaweeds - it gives them their characteristic olive-green colour. Studies show that fucoxanthin has anti-obesity, antioxidant, anti-cancer, anti-diabetic and anti-photoageing properties. (Ref. 4)

β-carotene is found in significant amounts in brown, green & red seaweeds, and further contributes to their medicinal profile. As we know, beta-carotene has strong anti-oxidant properties and thus may help to fight cancer, heart disease, arthritis and other medical conditions. (Ref. 1)

Seaweeds, and especially green macro-algae, also contain chlorophylls incl. chlorophyll a & b as well as pheophytins. Chlorophylls are potent biologically active pigments which have been shown to demonstrate anti-cancer effects, most likely thanks to their antioxidant, mutagen-trapping and detoxification properties. (Ref. 1)

Polyphenols are compounds which, like pigments, are thought to exhibit antioxidant properties. (Ref. 5)

Seaweeds are rich sources of polyphenols. As an example, brown seaweeds have a high content of polyphenlos called phlorotannins which can fight inflammation and microbial infections. (Ref. 6) Some other polyphenols found in seaweeds are catechin, epicatechin, epigallocatechin gallate, gallic acid. (Ref. 7)

Most recent research also suggests that high levels of polyphenols from a variety of brown seaweeds can be potentially used as a remedy for cancer treatment. (Ref. 8)

Polyphenols are the very compounds that give seaweeds their characteristic aroma and flavour, while pigments endow them with colours.

So, while pigments & polyphenols in seaweeds don't carry much of a calorific value, they have many medicinal & healing properties. Staple foods - such as rice or potatoes - don't compete with seaweeds in this respect, since their chemical structure is much simpler, and their main function being a source of calorie-rich fuel for the body - rather than anything else.

Minerals & Trace Elements

beautiful seaweed © Ryan Poplin

One of the major advantages of consuming seaweeds is the fact that they are marine-based plants, and they offer many unique minerals & trace elements that are not found in terrestrial plants (or found there in insufficient amounts).

For one reason or another, traditional nutritional advice has always been focused on vitamins, and much less so on other nutrients. Nowadays though, we hear a lot more about the importance of minerals & trace elements for stronger health, and recommendations to incorporate them into our diets. This is a very positive development.

Due to modern growing, cooking & processing practices, much of the raw foods' nutritional value is lost in the process, and as a result we get low-quality nutrition that is often lacking in most basic nutrients.

From this perspective, seaweeds are an excellent source of marine nutrition.

Seaweeds are exceptionally rich in all sorts of essential minerals including calcium, magnesium, potassium, phosphorus and sulphur. For comparison, some species of seaweeds have 14 times more calcium than cows milk, and 8 times more magnesium than any land vegetable. (Ref. 9)

Among trace elements, seaweeds have: iodine, boron, zinc, iron, germanium, selenium, silicon, lithium, manganese, copper, gold and a lot more. (Ref. 9)

One of the most outstanding sea-derived trace elements is certainly iodine. According to one statistic, some seaweed species may have up to 100 times more iodine than most terrestrial vegetables. (Ref. 9)

Seaweeds also have a very high content of iron, which is especially useful for people who don't consume red meat.

Other General Seaweed Nutrition

As a complete functional food, seaweeds contain all essential nutrients required for healthy work of the human body.

They are valued for a very high antioxidant content.

Here is a quick breakdown of seaweed nutritional profile (Ref. 1 & 9):

Vitamins: A (incl. antioxidant carotenoids), B1, B2, B3, B9, B12, C (antioxidant), D, E (antioxidant tocopherols), H (biotin), K.

Fatty acids: omega-3, omega-6, omega-9; alpha-linolenic acid, eicosapentenoic acid, arachidonic acid, linoleic acid, oleic acid, palmitic acid, hexadecatetraenoic acid, octadecatetraenoic acid.

Amino acids: alanine, arginine, aspartic acid, cystein & cystine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, valine.

Enzymes: protease, lipase, carbohydrase.

Polysaccharides form part of the carbohydrate/fibre content of seaweeds; and their minerals & trace elements have been mentioned above.

Some other compounds in seaweeds are sterols (ex., fucosterol in brown seaweeds), phycobiliproteins (protein-pigment complexes, incl. phycobilins, phycocyanins) and betaines. Sterols are an important group of steroids; phycobiliproteins may even have antioxidant properties; and betaines are believed to help with digestion and protect against cellular stresses.

Seaweed Health Benefits

Current research suggests that a lot of seaweeds' health-improving potential stems from their exceptional abundance of sulfated polysaccharides.

We know that the secret to beneficial effects of many healing plants is a synergistic action of all their unique chemical compounds. Polysaccharides, on their own, demonstrate some amazing medicinal properties. But they also work in perfect harmony with pigments & polyphenols, minerals & trace elements, plus an endless number of vitamins, fats, proteins and other constituents, to deliver the health benefits that we can all enjoy.

Health Benefits of Sulfated Polysaccharides

Most prominently, sulfated polysaccharides offer the following biological features (Ref. 2, 10, 11 & 12):

  • Anti-oxidant, anti-tumour & anti-proliferative, anti-mutagenic, anti-inflammatory, immunomodulatory, antithrombotic, anticoagulant, antibacterial, antiviral, lipid-lowering, anti-protozoan, anti-aging, cell-regenerative.

Sulfated polysaccharides are very complex chemical structures which are still being studied by many researchers around the world. Of course, nature offers us so many wonderful, chemically rich plants - and we are still a long way away from complete understanding of their specific mechanisms.

But what we do know is that sulfated polysaccharides may function as prebiotics. (Ref. 3)

The concept of prebiotics is a relatively new one - it was, in fact, introduced only in 1995. Here is how original authors define prebiotics:

Prebiotics are nondigestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacterial species already resident in the colon, and thus attempt to improve host health. Intake of prebiotics can significantly modulate the colonic microbiota by increasing the number of specific bacteria and thus changing the composition of the microbiota. (Ref. 13)

In other words, prebiotics must: 1) be resistant to digestion in the upper gastro-intestinal tract and therefore resistant to acid and enzymatic hydrolysis, 2) be a selective substrate for the growth of beneficial bacteria and therefore result in a shift in the profile of the microflora, and 3) induce systemic effects that are beneficial to host health. (Ref. 3)

Our conclusion based on some preliminary research is that, functioning as prebiotics, marine-based sulfated polysaccharides may help stimulate the growth of billions of beneficial bacteria within the gastro-intestinal tract.

And, as we know, healthy digestion is one of the most important steps towards stronger health. (Ref. 3) So, boosting the work of the digestive system is one notable path through which marine polysaccharides can help us achieve great health.

But, naturally, there may be many other diverse, and more direct, mechanisms of action via which polysaccharides can do their magic. (Ref. 2)

Health Benefits of Other Seaweed Compounds

Seaweeds are an incredibly abundant source of human nutrition - and they sure offer one of the best natural solutions to a whole host of medical conditions.

They contain a complete set of essential nutrients, and loads of non-essential ones, without which human life simply cannot exist. Essential nutrients, such as vitamins & minerals, cannot be produced by our bodies - they have to come from food. So, obtaining these nutrients in their organic, unprocessed form is a step in the right direction.

Essential nutrients are responsible for many biological functions within the body. Fighting off free radicals that roam inside the body is probably one of the most vital ones.

Many essential nutrients, ex. vitamins A, C & E, are antioxidants that scavenge such free radicals. The body relies upon them for keeping it cleansed. Oxidative stress places a huge burden on our systems. Antioxidants neutralise oxidative stress and protect the body against chronic disease.

Pigments & polyphenols, although non-essential compounds, are powerful antioxidants as well.

Much of our food is now deficient in many essential minerals & trace elements. For example, iodine fights infections and supports thyroid function, yet it is mostly absent from our diets for many different reasons. Other chemicals, ex. selenium, zinc & germanium, are now better understood, and are believed to perform a number of supportive biological functions too; yet - just like for iodine - modern foods don't contain sufficient amounts of them either.

Enzymes, on the other hand, are the sparks of life that set the process of cellular energy creation in motion. Seaweeds are rich in enzymes as well.

All of these great chemicals make seaweeds an ideal superfood for a thorough detoxification of our systems.

All of these chemicals come together to deliver health-boosting & disease-fighting benefits that we look at further down in this article.

Seaweed Benefits for Cancer

Cancer is one of the most devastating medical conditions of modern times, that's for sure.

It is very much an environmental disease. At some point, the body becomes totally overwhelmed with all the environmental toxins coming from water, air, food & external stress, and it gives in to this terrible condition.

It appears that seaweeds may provide natural and effective support with cancer treatment. Researchers point to the uniqueness of many seaweeds' compounds and chemical structures that are believed to fight cancer. (Ref. 7)

Here is an interesting example. Japanese people have one of the highest rates of seaweed consumption in the world. An occurrence of breast cancer in Japanese women is nearly 6 times lower than in American women - 20 cases of breast cancer per 100,000 women in Japan, as compared to 118 cases of breast cancer per 100,000 women in USA. Researchers believe that this is achieved thanks to much higher rates of seaweed consumption in Japan. (Ref. 14)

Fucoidan - a truly outstanding sulfated polysaccharide found in seaweeds - has been shown to kill human breast cancer cells, in a research study. (Ref. 15) Further research suggests that iodine may be another unique chemical that may help fight breast cancer as well. (Ref. 16)

Of course, seaweeds are pure whole foods and are therefore a very safe remedy to take, as compared to traditional pharmaceutical cancer treatments. One study reports that red seaweeds Eucheuma cottonii were at least 27% more efficient at suppressing breast tumour growth in rats, without any toxicity to the liver and kidneys, than tamoxifen - a pharmaceutical cancer drug that is also known to have many harmful side effects. (Ref. 17)

Seaweeds have also been shown to help with many other types of cancer including: liver cancer, lung cancer, gastrointestinal cancer, colorectal cancer, skin cancer (melanoma), leukemia, lymphoma. (Ref. 18, 19, 20, 21 & 22)

The fact that seaweeds are powerful detoxifying foods certainly helps with cancer control as well.

Seaweed Benefits for Cardiovascular Disease, Obesity & Diabetes

Cardiovascular disease has also reached truly epidemic proportions globally.

Cardiovascular disease is often preceded by a so-called metabolic syndrome which is characterised by high blood pressure and a large waistline, among several other things. (Ref. 23)

Evidence suggests that seaweeds can be an effective aide here too. As an example, participants in one study who took a daily 4 - 6g dose of Undaria pinnatifida (Wakame) over a 2-months period were able to achieve decreased blood pressure and reduced waist circumference. (Ref. 24)

A very interesting chemical here is fucoxanthin, which is a pigment carotenoid found in brown seaweeds. Fucoxanthin specifically acts to reduce main cardiovascular & metabolic risk factors - obesity, diabetes, high blood pressure, chronic inflammation, plasma and hepatic triglyceride, and cholesterol concentrations. (Ref. 4)

Excessive weight is a prominent feature of cardiovascular disease.

Fucoxanthin helps fight obesity through oxidation of fatty acids and heat production in white adipose tissues. (Ref. 4)

In addition to its anti-obesity effect, fucoxanthin can also improve insulin resistance in a number of ways and thus function as an anti-diabetic remedy as well. (Ref. 4)

It is not only fucoxanthin, of course, but a whole combination of all the nutrients that make seaweeds work hard for the heart.

Polyunsaturated fatty acids have been highlighted many times as valuable nutrients for the cardiovascular system. Seaweeds have a perfect balance of omega-3 and omega-6 fatty acids, which offers a great protection against inflammation and cardiovascular disease. (Ref. 25)

Seaweeds' antioxidant action also, undoubtedly, helps with control of heart conditions.

Seaweed Benefits for Thyroid Disorders

Many species of brown seaweeds contain high amounts of iodine - a trace element which is often missing from land-growing plants.

Iodine is very important for thyroid health and works as an activator of thyroid function. (Ref. 4)

This element is essential for the synthesis of the thyroid hormones, thyroxine (T4) and triiodothyronine (T3), by the thyroid gland. These thyroid hormones modulate lipid, carbohydrate, and protein metabolism and oxygen consumption by cells, and are essential for normal development of the nervous, cardiovascular, immune, and reproductive systems. (Ref. 26)

Iodine deficiency often results in the weak thyroid function called hypothyroidism, or underactive thyroid. Iodine deficiency in pregnancy may also lead to neurological under-development in children. (Ref. 26)

Since iodine is not produced by the human body, it has to come from food. Iodized table salt and dairy products are often recommended as a source of iodine for human consumption. However, we know that table salt itself is a highly unhealthy product, and many people are allergic to dairy products.

Seaweeds are an excellent alternative source of food-state iodine. We encourage everyone to explore this opportunity for an all-natural iodine source.

Seaweed Benefits for Liver & Kidney Disease

Marine polysaccharides & pigments show great promise for liver and kidney conditions as well.

Fucoidan (polysaccharide) from brown seaweeds has shown an ability to inhibit liver fibrosis (fibrous tissue growth that occurs after a toxic or pathogen impact on the liver), reduce the damage from liver ischemia (insufficient blood or oxygen supply to the liver) and help with the regeneration of severely damaged livers. (Ref. 27)

Fucoidan can also reduce general inflammation of the kidneys, prevent chronic renal failure and possibly assist with the problem of kidney stones. (Ref. 27)

Fucoxanthin (pigment carotenoid), on the other hand, has been shown to reduce body weight, body fat & liver fat content as well as deliver improved liver function tests in obese women diagnosed with non-alcoholic fatty liver disease and those presenting with normal liver fat. (Ref. 28)

Researchers suggest that the reduction of liver fats specifically might be due to fucoxanthin encouraging higher levels of docosahexaenoic acid (DHA) in the liver. DHA works by reducing the activity of hepatic enzymes in fatty acid synthesis and increasing hepatic fatty acid oxidation. (Ref. 28)

A study on damaged liver cells demonstrated that fucoxanthin may increase the levels of glutathione (a powerful antioxidant) and decrease intracellular reactive oxygen species (free radicals) and DNA damage in liver cells. (Ref. 28)

The liver and kidneys are major purifying and detoxifying organs of the human body. Therefore, their nutritional support is absolutely vital for strong health. Seaweeds could be an excellent remedy here too.

Seaweed Benefits for Neurological Disorders

Treatment of neurodegenerative conditions presents a real challenge to professionals dealing with them, and individuals living with them. Some of such conditions are: multiple sclerosis, Alzheimer’s disease, Parkinson’s disease, cerebellar ataxia.

A huge part of the "incurability" of neurodegenerative disorders lies in the fact that they are caused by malfunction of the brain and central nervous system. We know that the brain-blood barrier doesn't allow for an easy access of nutrients to this vital system of the body, which makes it harder for nutritional therapy (or any other restorative therapy) to work.

Oxidative stress in the central nervous system has been demonstrated to cause lipid peroxidation, DNA & protein damage, excitotoxicity and - ultimately - neuronal death. (Ref. 29)

Antioxidant potential (that is, acting against oxidative stress) of numerous seaweed species has been proposed as one major solution for such oxidative stress. This antioxidant action of marine algae ties in with their general detoxification capacity, too. (Ref. 29)

Another major cause of neurodegeneration is chronic inflammation of the central nervous system. Several studies have demonstrated anti-neuroinflammatory potential of marine algae, again highlighting an incredible healing value of sulfated polysaccharide fucoidan here. (Ref. 29)

Researchers also draw our attention to the action of seaweeds against neuro-toxins (ex., beta-amyloid peptides) which are, of course, damaging to the function of the central nervous system. (Ref. 29)

So, we can clearly see an under-utilised potential of seaweeds for neuroprotection here.

Seaweed Benefits for Infections

Seaweeds are an amazingly diverse functional food. There is no surprise that they are now being tapped for potential treatment of all sorts of infections.

This is especially valuable since the use of conventional antibiotics often proves to be inefficient and damaging to the beneficial bacterial flora of the intestinal tract, and is fraught with the long-term resistance by harmful bacteria.

Infections themselves may lead to an onset of many medical conditions - including chronic fatigue syndrome, myalgic encephalomyelitis (ME) and fibromyalgia.

Hepatitis C virus infection affects 170mln. people worldwide. It is considered to be incurable, develops over a period of many years and often leads to chronic liver degradation, liver cirrhosis & hepatocellular carcinoma. (Ref. 30)

In one 12-months-long study, patients with chronic liver disease caused by hepatitis C virus were treated with a fucoidan extract and showed marked improvements in some bio-indicators related to the disease. In a "tube test" (in vitro), fucoidan was also shown to effectively suppress intracellular replication of hepatitis c virus genome. (Ref. 30)

Other findings suggest that fucoidan may inhibit virus adsorption to the cell surface by binding itself to the cell surface, with subsequent prevention of cell infection. This was demonstrated in a case with parainfluenza virus type 2. (Ref. 31)

Experts believe that herpes simplex virus may also be treated with sulfated polysaccharides, including fucoidan. (Ref. 12 & 32)

In a "tube test" study conducted in Argentina on the effects of seaweeds on the human immunodeficiency virus (HIV), extracts of fucoidans from the brown seaweed Adenocystis utricularis demonstrated potent anti-HIV activity, which was most likely due to a blockade of early events of viral replication. (Ref. 33)

A sulfated polysaccharide from red seaweed, iota-carrageenan, may be a potent anti-rhinoviral substance, and can potentially prevent the common cold with symptoms such as sore throat, rhinitis, nasal congestion, and cough. (Ref. 34)

Dengue virus is mostly present in tropical regions of the planet. One Brazilian study showed that several seaweed extracts were able to fight Dengue virus in cells, and appeared to act at an early stage of the virus infection cycle. (Ref. 35)

Malaria is an infectious disease caused by Plasmodium falciparum, a protozoan parasite. Malaria is widely spread in tropical and subtropical areas. Fucoxanthin has been shown to have powerful antiplasmodial action. (Ref. 28)

Seaweed Benefits for Skin & Bones

Skin is the largest organ of the human body. Not only does it protect the body from external irritants, it is also vital for its cleansing because it removes bodily waste through sweat.

Collagen is one of the main constituents of all connective tissue including skin.

One study reports that extracts of polysaccharides from kelp (brown seaweeds) were able to increase the biosynthetic activity of collagen by up to 80%. (Ref. 36)

Another study found that fucoxanthin delivered a protective effect against ultraviolet-induced skin photoaging in mice. (Ref. 4) This is a very valuable finding since the risk of UV irradiation in people is very high - taking into account current environmental issues.

In another experiment, patients with atopic dermatitis who wore clothing made of fabrics with incorporated seaweeds showed significant improvements in their skin condition. (Ref. 37) Fucoidan, on its own, has also been shown to help ease the effects of atopic dermatitis. (Ref. 38)

A cosmetic product containing oligosaccharides from seaweeds was shown to greatly reduce mild acne in a group of patients over a period of 8 weeks. (Ref. 39)

Seaweeds may provide an indispensable support for bone-related diseases, too.

This is because marine plants have an incredible number of minerals & trace elements that are extremely important for bones. Deficiency of these elements in land-growing foods often leads to bone-related conditions. Some of the notable chemicals here are magnesium, boron, selenium, germanium, silicon, to name just a few.

But other seaweed compounds are very useful as well.

Fucoidan reduces pain and has been shown to help with inflammatory bone-related conditions such as osteoarthritis. (Ref. 27)

Another seaweed compound - fucoxanthin - can also be helpful for the prevention of bone diseases including osteoporosis and rheumatoid arthritis. (Ref. 28)

Seaweed Benefits for Weight Loss

Obesity is a growing global epidemic that underlies many other chronic conditions such as diabetes and cardiovascular disease. Over-processed foods contain empty calories, and very little in respect of vitamins, minerals and other essential nutrients. Such foods usually deliver low-value energy, for a short period of time - quickly leading to feelings of hunger and cravings for more unhealthy foods.

Seaweeds have been showing real promise here as well.

Below are just several ways that make seaweeds so effective in terms of weight management:

  • First, seaweeds provide a complete broad-spectrum, marine-based nutrition. They provide us with everything we need in a natural, food-state form. Our bodies understand this nutrition very well, process it perfectly and reduce our appetite, keeping hunger at bay for longer.
  • Second, prebiotics in seaweeds enable proper digestion of food in the gastrointestinal tract. Prebiotics also modulate lipid (fat) metabolism. (Ref. 13)
  • Third, seaweeds contain many unique chemicals that do their magic as well. As just one example, fucoxanthin encourages oxidation of fatty acids and heat production in white adipose tissue, leading to fat loss. (Ref. 4)

We are certain that science will be coming up with more discoveries about the healing wonders of seaweeds and their mechanisms against obesity.

As for now, it is not only science, but plenty of anecdotal evidence that also proves efficiency of seaweeds as an anti-obesity food.

Seaweed Benefits: Other Interesting Points

Seaweeds can be useful in hundreds of different ways. Here are just some of them:

  • Fucoidan generally protects against acute and chronic inflammation. (Ref. 27)
  • Fucoidan provides protection against radiation. (Ref. 27)
  • Fucoxanthin protects blood vessels of the brain and eyes. (Ref. 28)
  • Brown kelp (Fucus vesiculosus) modulates endocrine hormones and may contribute to a lower incidence of hormone-dependant cancers. (Ref. 40)
  • Seaweeds favorably alter estrogen and phytoestrogen metabolism. (Ref. 41)
  • Marine algae show an anti-allergic action. (Ref. 42)
  • Red seaweeds can prevent oxidative DNA damage. (Ref. 43)
  • Brown seaweeds may contribute to a general reduction in appetite. (Ref. 9)
  • Brown seaweeds can ameliorate snake envenomation. (Ref. 27)
  • Seaweed compounds mixed with water have been used as a substitute for whole blood in transfusions in over 100 operations in Japan. (Ref. 7)
  • Numerous studies report that seaweeds have no known toxicity issues. In other words, they are a very safe food to take.

Seaweeds for Tiredness & Chronic Fatigue Syndrome

In our tiredness article, we discuss the causes of unexplained tiredness & chronic fatigue syndrome that could be traced down to nutrient deficiencies.

We have shown that deficiencies of various vitamins, minerals and other nutrients could be a cause of tiredness and chronic fatigue syndrome.

Yet again, seaweeds - with many unique marine-derived nutrients - could provide a real boost to our systems and help deal with tiredness on a fundamental level.

We have also demonstrated that numerous toxins can cause chronic fatigue as well. In this regard, seaweeds could be a powerful detoxification tool too.

In other words, seaweeds are a great all-round food that could be used over time to treat tiredness & chronic fatigue.

Seaweeds or Sea Salt?

Many nutritionists currently recommend the use of sea salt as a source of minerals & trace elements that are often missing from land-growing foods. The consensus here is that table salt should be totally dropped as a very unhealthy product, and sea salt introduced as a replacement for table salt.

We also believe that sea salt is a great source of some essential marine nutrients. These nutrients come from sea salt in an inorganic form.

On the other hand, seaweeds are marine plants which absorb minerals & trace elements directly from the sea, process them and deliver them to us in a purely organic form - as opposed to the inorganic form of sea salt.

So, if we consume sea salt, our bodies get inorganic nutrients straight from the sea; if we consume seaweeds, our bodies get organic marine nutrients instead.

Some experts say that our bodies absorb different forms of nutrition differently; others say that it doesn't matter whether that nutrition is "organic" or "inorganic".

A big advantage of organic minerals over inorganic ones is that organic minerals are chelated (bound) to other compounds (often amino acids) in a plant, and are thus much easier transported and integrated into the cells than inorganic minerals.

My personal experience shows that over-consumption of sea salt (i.e., inorganic minerals) may lead to hard salt deposits on the bones, especially around the joints. This will never happen with seaweeds.

So, if you had to choose between sea salt or seaweeds, our recommendation would be to go with seaweeds. Especially that they can be added to foods as an alternative to salt.

Written and researched by:     Irina Bright
Original publication date:     2013
Republication date:     2020


1. Lordan S, Ross RP, Stanton C. (June 14, 2011). Marine Bioactives as Functional Food Ingredients: Potential to Reduce the Incidence of Chronic Diseases. Published in Marine Drugs. 2011; 9(6):1056-1100. Retrieved July 8, 2013 from:

2. Seema Patel (September 2012). Therapeutic importance of sulfated polysaccharides from seaweeds: updating the recent findings. Published in 3 Biotech. Retrieved July 8, 2013 from:

3. Laurie O'Sullivan, Brian Murphy, Peter McLoughlin, Patrick Duggan, Peadar G. Lawlor, Helen Hughes, and Gillian E. Gardiner (July 2010). Prebiotics from Marine Macroalgae for Human and Animal Health Applications. Published in Marine Drugs. Retrieved July 8, 2013 from:

4. Nicolantonio D'Orazio, Eugenio Gemello, Maria Alessandra Gammone, Massimo de Girolamo, Cristiana Ficoneri, and Graziano Riccioni (March 2012). Fucoxantin: A Treasure from the Sea. Published in Marine Drugs. Retrieved July 8, 2013 from:

5. Kajal Chakraborty, Nammunayathuputhenkotta Krishnankartha Praveen, Kodayan Kizekadath Vijayan, and Gonugontla Syda Rao (January 2013). Evaluation of phenolic contents and antioxidant activities of brown seaweeds belonging to Turbinaria spp. (Phaeophyta, Sargassaceae) collected from Gulf of Mannar. Published in Asian Pacific Journal of Tropical Biomedicine. Retrieved July 8, 2013 from:

6. Graciliana Lopes, Carla Sousa, Lus R. Silva, Eugnia Pinto, Paula B. Andrade, Joo Bernardo, Teresa Mouga, and Patrcia Valento (February 2012). Can Phlorotannins Purified Extracts Constitute a Novel Pharmacological Alternative for Microbial Infections with Associated Inflammatory Conditions? Published in PLoS One. Retrieved July 8, 2013 from:

7. N. Sithranga Boopathy and K. Kathiresan (February 2011). Anticancer Drugs from Marine Flora: An Overview. Published in Journal of Oncology. Retrieved July 8, 2013 from:

8. Sheeja Aravindan, Caroline R. Delma, Somasundaram S. Thirugnanasambandan, Terence S. Herman, and Natarajan Aravindan (April 2013). Anti-Pancreatic Cancer Deliverables from Sea: First-Hand Evidence on the Efficacy, Molecular Targets and Mode of Action for Multifarious Polyphenols from Five Different Brown-Algae. Published in PLoS One. Retrieved July 8, 2013 from:

9. Irina Bright (2013). Seagreens. Published in Retrieved July 8, 2013 from:

10. Costa LS, Fidelis GP, Telles CB, Dantas-Santos N, Camara RB, Cordeiro SL, Costa MS, Almeida-Lima J, Melo-Silveira RF, Oliveira RM, Albuquerque IR, Andrade GP, Rocha HA (June 2011). Antioxidant and antiproliferative activities of heterofucans from the seaweed Sargassum filipendula. Published in Marine Drugs. Retrieved July 8, 2013 from:

11. Tiago H. Silva, Anabela Alves, Elena G. Popa, Lara L. Reys, Manuela E. Gomes, Rui A. Sousa, Simone S. Silva, Joo F. Mano, and Rui L. Reis (October 2012). Marine algae sulfated polysaccharides for tissue engineering and drug delivery approaches. Published in Biomatter. Retrieved July 8, 2013 from:

12. Misurcov L, Skrovnkov S, Samek D, Ambrozov J, Machu L (2012). Health benefits of algal polysaccharides in human nutrition. Published in Advances in food and nutrition research. Retrieved July 8, 2013 from:

13. Gibson GR, Roberfroid MB (June 1995). Dietary modulation of the human colonic microbiota: introducing the concept of prebiotics. Published in The Journal of nutrition. Retrieved July 8, 2013 from:

14. Jane Teas, Sylvia Vena, D. Lindsie Cone, and Mohammad Irhimeh (June 2013). The consumption of seaweed as a protective factor in the etiology of breast cancer: proof of principle. Published in Journal of Applied Phycology. Retrieved July 8, 2013 from:

15. Yamasaki-Miyamoto Y, Yamasaki M, Tachibana H, Yamada (September 2009). Fucoidan induces apoptosis through activation of caspase-8 on human breast cancer MCF-7 cells. Published in Journal of agricultural and food chemistry. Retrieved July 8, 2013 from:

16. Smyth PP (2003). Role of iodine in antioxidant defence in thyroid and breast disease. Published in BioFactors (Oxford, England). Retrieved July 8, 2013 from:

17. Shamsabadi FT, Khoddami A, Fard SG, Abdullah R, Othman HH, Mohamed S (February 2013). Comparison of Tamoxifen with Edible Seaweed (Eucheuma cottonii L.) Extract in Suppressing Breast Tumor. Published in Nutrition and cancer. Retrieved July 8, 2013 from:

18. Yang L, Wang P, Wang H, Li Q, Teng H, Liu Z, Yang W, Hou L, Zou X (June 2013). Fucoidan Derived from Undaria pinnatifida Induces Apoptosis in Human Hepatocellular Carcinoma SMMC-7721 Cells via the ROS-Mediated Mitochondrial Pathway. Published in Marine Drugs. Retrieved July 8, 2013 from:

19. Mary JS, Vinotha P, Pradeep AM (2012). Screening for in vitro Cytotoxic Activity of Seaweed, Sargassum sp. Against Hep-2 and MCF-7 Cancer Cell Lines. Published in Asian Pacific journal of cancer prevention. Retrieved July 8, 2013 from:

20. Hyunkyoung Lee, Jong-Shu Kim, and Euikyung Kim (2012). Fucoidan from Seaweed Fucus vesiculosus Inhibits Migration and Invasion of Human Lung Cancer Cell via PI3K-Akt-mTOR Pathways. Published in PLoS One. Retrieved July 8, 2013 from:

21. Kim SK, Karagozlu MZ (2011). Marine algae: natural product source for gastrointestinal cancer treatment. Published in Advances in food and nutrition research. Retrieved July 8, 2013 from:

22. Hosokawa M, Kudo M, Maeda H, Kohno H, Tanaka T, Miyashita K (November 2004). Fucoxanthin induces apoptosis and enhances the antiproliferative effect of the PPARgamma ligand, troglitazone, on colon cancer cells. Published in Biochimica et biophysica acta. Retrieved July 8, 2013 from:

23. National Heart, Lung, and Blood Institute, US Department of Health and Human Services (November 2011). What is Metabolic Syndrome? Retrieved July 8, 2013 from:

24. Teas J, Balden ME, Chiriboga DE, Davis JR, Sarris AJ, Braverman LE (2009). Could dietary seaweed reverse the metabolic syndrome? Published in Asia Pacific journal of clinical nutrition. Retrieved July 8, 2013 from:

25. Vincent JT van Ginneken, Johannes PFG Helsper, Willem de Visser, Herman van Keulen, and Willem A Brandenburg (June 2011). Polyunsaturated fatty acids in various macroalgal species from north Atlantic and tropical seas. Published in Lipids in Health and Disease. Retrieved July 8, 2013 from:

26. Sarah G. Obican, Gloria D. Jahnke, Offie P. Soldin, and Anthony R. Scialli (August 2012). Teratology Public Affairs Committee Position Paper: Iodine Deficiency in Pregnancy. Published in Birth Defects Research. Retrieved July 8, 2013 from:

27. Janet Helen Fitton (September 2011). Therapies from Fucoidan; Multifunctional Marine Polymers. Published in Marine Drugs. Retrieved July 8, 2013 from:

28. Juan Peng, Jian-Ping Yuan, Chou-Fei Wu, and Jiang-Hai Wang (October 2011). Fucoxanthin, a Marine Carotenoid Present in Brown Seaweeds and Diatoms: Metabolism and Bioactivities Relevant to Human Health. Published in Marine Drugs. Retrieved July 8, 2013 from:

29. Ratih Pangestuti and Se-Kwon Kim (May 2011). Neuroprotective Effects of Marine Algae. Published in Marine Drugs. Retrieved July 8, 2013 from:

30. Naoki Mori, Kazunori Nakasone, Koh Tomimori, and Chie Ishikawa (May 2012). Beneficial effects of fucoidan in patients with chronic hepatitis C virus infection. Published in World Journal of Gastroenterology. Retrieved July 8, 2013 from:

31. Taoda N, Shinji E, Nishii K, Nishioka S, Yonezawa Y, Uematsu J, Hattori E, Yamamoto H, Kawano M, Tsurudome M, O'Brien M, Yamashita T, Komada H (December 2008). Fucoidan inhibits parainfluenza virus type 2 infection to LLCMK2 cells. Published in Biomedical research (Tokyo, Japan). Retrieved July 8, 2013 from:

32. Vo TS, Ngo DH, Ta QV, Kim SK (September 2011). Marine organisms as a therapeutic source against herpes simplex virus infection. Published in European journal of pharmaceutical sciences. Retrieved July 8, 2013 from:

33. Trinchero J, Ponce NM, Crdoba OL, Flores ML, Pampuro S, Stortz CA, Salomn H, Turk G (May 2009). Antiretroviral activity of fucoidans extracted from the brown seaweed Adenocystis utricularis. Published in Phytotherapy research. Retrieved July 8, 2013 from:

34. Andreas Grassauer, Regina Weinmuellner, Christiane Meier, Alexander Pretsch, Eva Prieschl-Grassauer, and Hermann Unger (September 2008). Iota-Carrageenan is a potent inhibitor of rhinovirus infection. Published in Virology Journal. Retrieved July 8, 2013 from:

35. Andrea Cristine Koishi, Paula Rodrigues Zanello, verson Miguel Bianco, Juliano Bordignon, and Claudia Nunes Duarte dos Santos (December 2012). Screening of Dengue Virus Antiviral Activity of Marine Seaweeds by an In Situ Enzyme-Linked Immunosorbent Assay. Published in PLoS One. Retrieved July 8, 2013 from:

36. Yu P, Chao X (January 2013). Statistics-based optimization of the extraction process of kelp polysaccharide and its activities. Published in Carbohydrate polymers. Retrieved July 8, 2013 from:

37. Park KY, Jang WS, Yang GW, Rho YH, Kim BJ, Mun SK, Kim CW, Kim MN (July 2012). A pilot study of silver-loaded cellulose fabric with incorporated seaweed for the treatment of atopic dermatitis. Published in Clinical and experimental dermatology. Retrieved July 8, 2013 from:

38. Yang JH (December 2012). Topical application of fucoidan improves atopic dermatitis symptoms in NC/Nga mice. Published in Phytotherapy research. Retrieved July 8, 2013 from:

39. Capitanio B, Sinagra JL, Weller RB, Brown C, Berardesca E (June 2012). Randomized controlled study of a cosmetic treatment for mild acne. Published in Clinical and experimental dermatology. Retrieved July 8, 2013 from:

40. Skibola CF, Curry JD, VandeVoort C, Conley A, Smith MT (February 2005). Brown kelp modulates endocrine hormones in female sprague-dawley rats and in human luteinized granulosa cells. Published in The Journal of nutrition. Retrieved July 8, 2013 from:

41. Teas J, Hurley TG, Hebert JR, Franke AA, Sepkovic DW, Kurzer MS (May 2009). Dietary seaweed modifies estrogen and phytoestrogen metabolism in healthy postmenopausal women. Published in The Journal of nutrition. Retrieved July 8, 2013 from:

42. Kim SK, Vo TS, Ngo DH (2011). Antiallergic benefit of marine algae in medicinal foods. Published in Advances in food and nutrition research. Retrieved July 8, 2013 from:

43. Yang JI, Yeh CC, Lee JC, Yi SC, Huang HW, Tseng CN, Chang HW (June 2012). Aqueous extracts of the edible Gracilaria tenuistipitata are protective against H2O2-induced DNA damage, growth inhibition, and cell cycle arrest. Published in Molecules (Basel, Switzerland). Retrieved July 8, 2013 from: