Seaweed: what are the health benefits?

Characteristics of the algae :

  • Excellent source of antioxidants;
  • Rich in vitamin B12 and iodine;
  • Interesting content of dietary fibres;
  • Promotes cardiovascular health.

 Nutritional and caloric values of seaweed

Seaweed is mainly consumed in Asia. In the West, they are used almost exclusively in sushi or as a condiment. However, the nutritional value of seaweed is exceptional and it has a refined taste. A new vegetable to discover.

NutrientsRaw kelp and kombu, 100 gRaw Wakame, 100 gDried dulse and nori, 10 g
Protein1,7 g3,0 g3,6 g
Carbohydrates9,6 g9,1 g2,4 g
Lipids0,6 g0,6 g0,2 g
Dietary fibres1,3 g0,5 g0,2 g

Focus on the micronutrients contained in seaweed

Seaweed is particularly rich in micronutrients, all of which are essential for the proper functioning of the body. Among the vitamins and minerals present in quantity in seaweed, we can mention :

  • Vitamin A: raw or dried dulse and nori are excellent sources of vitamin A for women and good sources for men;
  • Vitamin B12: raw and dried dulse and nori are excellent sources of vitamin B2. Raw wakame is an excellent source for women, but a good source for men. Raw kelp and kombu are good sources;
  • Vitamin B9: seaweeds are all excellent sources of vitamin B9 (folate);
  • Vitamin C: raw dulse and nori are excellent sources of vitamin C for women, but good sources for men. Dried dulse and nori are good sources;
  • Vitamin K: all seaweeds, except dried dulse and nori, are excellent sources of vitamin K;
  • Vitamin B5: raw wakame is a good source of vitamin B5 (pantothenic acid);
  • Copper: raw dulse, nori and wakame are excellent sources of copper. Dried dulse and nori, as well as raw kelp and kombu are good sources;
  • Iron: raw kelp, kombu and wakame are excellent sources of iron for men and good sources for women. Raw and dried dulse and nori are good sources of iron for men and for women;
  • Manganese: raw and dried dulse and nori, as well as raw wakame are excellent sources of manganese. Raw kelp and kombu are good sources for women and sources for men;
  • Magnesium: kelp, kombu and raw wakame are excellent sources of magnesium;
  • Calcium: raw kelp, kombu and wakame are good sources of calcium;
  • Phosphorus: raw wakame is a good source of phosphorus;
  • Zinc: Raw kelp, kombu, dulse and nori are good sources of zinc for women.

 The benefits of seaweed

It is known that regular consumption of vegetables (including seaweed) helps maintain good health and prevent a host of ailments. The particular action of seaweed on cardiovascular diseases, diabetes, hypercholesterolemia and hypertension would be due, among other things, to the antioxidants, fibers and phytosterols that it contains.

The benefits of seaweed on certain cancers

Studies have shown that different algae or their compounds have the capacity to counter the development of mammary tumours in animals and to induce the death of certain cancerous cells in vitro. Algae, which tend to oppose estrogen, could be a protective factor in the development of hormone-dependent cancers such as breast or prostate cancer.

Epidemiological studies indicate that populations consuming an Asian-type diet have a lower incidence of these cancers compared to populations consuming a North American-type diet. This finding has been largely attributed to the high consumption of soy in Asians, but the high consumption of seaweed in this population may also play a role. In addition, a deficiency of iodine and selenium, two nutrients abundant in seaweed, may play a role in breast cancer formation. However, the actual role of seaweed in the prevention of hormone-dependent cancers has yet to be determined.

In vitro study published in 2010 shows that fucoidan (a sugar found in brown seaweed) induces the death of human leukemia cells through the production of nitric oxide (NO), among other things. The authors mention that fucoidan could increase the effectiveness of traditional chemotherapy agents in causing cancer cell death. In another in vitro study, fucoidan destroyed breast cancer cells. According to the authors, fucoidan is a promising compound in the prevention of breast cancer and its therapeutic value deserves to be analyzed.

The antioxidant power of algae

Several extracts of brown, red and green algae grown in Europe or Asia have demonstrated antioxidant activity in vitro. Their antioxidant composition and antioxidant capacity vary depending on several factors, such as the depth at which they grow and their degree of exposure to ultraviolet (UV) light. Seaweeds contain a variety of antioxidant compounds including carotenoids (lutein and zeaxanthin), flavonoids (catechins), phenolic acids (tannins), and certain vitamins (primarily vitamins C and E).

Interesting fiber content

Seaweed contains interesting amounts of fibre, especially in soluble form. Depending on the variety, a portion of fresh seaweed can contain up to 8% of the daily recommended amount of fibre. Dried seaweed contains 35% to 50% of its weight in the form of fibre. In general, a diet rich in dietary fibre can contribute to the prevention of cardiovascular disease, as well as the control of type 2 diabetes and appetite. The fiber in seaweed may be more effective in lowering blood cholesterol and hypertension than fiber from other sources.

The brown seaweed (laminaria longicruris) found in the Gulf of St. Lawrence, more specifically in the Gaspé region of Quebec, is particularly rich in two types of soluble fibre: laminaran (a non-digestible sugar of the ß-glucan family) and fucans. These compounds have several interesting biological properties. Laminaran is said to fight against tumours and modulate the immune response. Fucans have anticoagulant, anti-inflammatory and antiviral properties. A team of Quebec researchers has observed that the harvesting period of the algae had an influence on their laminaran and fucan content.

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Seaweed, a valuable ally in reducing cholesterol levels

Wakame and nori contain phytosterols. These compounds are chemically similar to cholesterol and prevent the absorption of cholesterol into the body. Consumption of phytosterols may reduce blood cholesterol levels, particularly LDL cholesterol (bad cholesterol). However, to observe such effects, large quantities of dried seaweed would have to be consumed daily, and no study has so far evaluated the impact of phytosterol consumption from seaweed on blood cholesterol.

A good source of vitamin B12?

The vitamin B12 found in seaweed is often considered inactive and therefore not assimilated by the body. However, researchers have shown that nori contains significant amounts of biologically active vitamin B12. Rats with a vitamin B12 deficiency were fed a diet enriched with nori for 20 days; the researchers observed an increase in vitamin B12 levels in their liver.

It should be noted, however, that these animal results are not necessarily transferable to humans. The absorption and metabolism of vitamin B12 from marine plants, such as seaweed, will need to be evaluated in humans. The method of drying the seaweed would likely influence the bioavailability of this vitamin. Air-drying would render vitamin B12 “inactive”, while freeze-drying (cold drying) would not have this effect.

In light of these studies, and given the different varieties of seaweed consumed, it is advisable not to rely on seaweed to meet our daily vitamin B12 needs. Vegetarians, whose intake of this vitamin is often deficient, will have to turn to other foods (especially foods enriched with this vitamin, such as vegetable drinks) to meet their needs.

A word from the nutritionist

It can take some time for the body to get used to seaweed, whose laxative effects are very real. It is recommended to include them gradually in your diet. Eventually, they could constitute up to 10% of the food ration, as is the case in Japan. However, when added to legumes while they are cooking, seaweed has the property of reducing cooking time and making them more digestible (reducing flatulence) while refining their taste and texture. This action would be attributable to their richness in glutamates.

 How to choose the right seaweed?

Seaweeds are a heterogeneous group of hundreds of plants living in fresh or salt water. We could say that they are aquatic vegetables. Their size varies from less than a millimetre for microscopic algae to a few hundred metres for giant kelp.

Edible seaweeds are usually classified by colour: green, brown and red. The most common commercially available seaweeds are sea lettuce, sea hair, dulse, Irish moss (from which carrageenan is extracted), sea bean, nori (used in sushi), wakame, hijiki, kelp and kelp.

Identity card of the seaweed

  • Family: Fucaceae, Laminariaceae, Ulvaceae, Himanthaliaceae, etc. ;
  • Origin: Asia ;
  • Season: May to November;
  • Color: green, brown or red;
  • Flavour: iodized.

The different types of algae

  • Fresh seaweed must be rinsed well to desalinate it;
  • Dry seaweed is sold in sheets, ribbons, pieces or powder. You can also find seaweed in brine or canned form in specialized shops;
  • The appearance and texture of canned seaweed is similar to pureed spinach.

The conservation of algae

Fresh seaweed can be stored for a few days in the refrigerator. Dried seaweed should be kept in an airtight container, away from heat and light. The shelf life of packaged products is generally 2 years, although in Japan, they are willingly kept much longer because the seaweed improves with time.

 How to prepare the seaweed

Seaweed can be eaten barely cooked and still crunchy, or cooked for a very long time and almost melted in the dish. Although they are usually served with fish, there is nothing to stop them being cooked with poultry or meat.

The rehydration of algae

The rehydration time for seaweed varies depending on the type. Sea hair, sea lettuce, porphyry and dulse take only a few minutes; sea spaghetti and hijiki will take 15 minutes; kelp, wakame and kelp 30 to 60 minutes. You can use a liquid other than water to rehydrate them: white wine, vinegar, beer, etc. Avoid, however, red wine or red wine vinegar, whose tannin reacts with iodine.

Nori can be dry-roasted by passing it over a gas stove flame or on an electric hotplate. In Japan, this is a common technique for making sushi, fine omelettes, or other culinary uses of this seaweed.

In which preparations should seaweed be used in the kitchen?

  • Add seaweed at the end of cooking to soups, cooked vegetables, legumes, rice, pasta;
  • Season seafood pizzas with it;
  • It can be added to butter sauces, mayonnaise, salad dressings, mustard;
  • Cut the seaweed into thin strips, grill it and add it to a cooked and cooled cabbage or soba noodle salad. Serve the noodle salad with chopped chives, Japanese mustard and a dressing;
  • Add 1 tbsp. of ground seaweed to an omelette mixture or, for a more elaborate dish, make a Japanese-style omelette with a few layers of eggs interspersed with nori;
  • Incorporate seaweed into bread, biscuit, pancake and, why not, cake and muffin preparations. Some people do not hesitate to make ice creams and sorbets with seaweed, especially since it has a gelling power that allows the preparation to “set”;
  • Quiche marine: fry a shallot in butter or oil, add pieces of rehydrated seaweed, cook for a few minutes, then put this preparation in a shortcrust pastry. Cover with a mixture of beaten eggs and a little cream and sprinkle with grated parmesan or garnish with thin slices of salmon. Bake in the oven.
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Seaweed and seafood: a successful marriage

  • Shrimp and scallops can be steamed, wrapped in a piece of rehydrated seaweed;
  • You can also stew a whole fish by placing it on a kelp leaf in a pan. Add a little water, cover and leave to simmer on the fire for about twenty minutes;
  • Rehydrate a dry seaweed, wrap it around a fish and bake or steam it. Or stuff the fish with seaweed. Or marinate the fish for 30 minutes in lemon juice with a few spoonfuls of seaweed powder before cooking.

Seaweed in salads

To make a shrimp, cucumber and wakame salad: cut a cucumber lengthwise, remove the seeds and cut into thin slices. Put it to drain with a little salt in a colander, rinse with water and drain. Soak the seaweed in cold water for ten minutes, drain and mix with the slices of cucumber, cooked shrimp and thin slices of ginger. Season with rice vinegar, dashi, soy sauce, honey and mirin.

The Asian version of seaweed

  • Dashi: this essential broth of Japanese cuisine is used in a multitude of dishes, from soups to stews and sauces. You can find instant broth, which you just have to dilute with water, but it is very easy to prepare yourself. For 2 litres of water, you need about 40 g of kelp and 60 g of bonito flakes (a preparation made from a fish of the tuna family that can be found in Asian grocery stores). Wipe the kelp with a damp cloth and put it on the fire in a pan with the water. As soon as the first bubbles appear, check the texture of the kelp by pressing your thumbnail into the thickest part of it. If it penetrates easily, the kelp is ready. If not, return to a simmer for a few minutes, but do not boil. Reserve the kelp. Add half a cup of cold water to lower the temperature of the broth, add the bonito flakes, bring to a boil and remove from heat. Let the bonito flakes settle to the bottom, then strain without pressing;
  • Tofu and wakame seaweed consommé: rehydrate the seaweed by placing it in cold water for about ten minutes, drain it and cut it into coarse strips, removing the hard ribs if necessary. Slice the tofu, then cut it into cubes or rectangles. Arrange the seaweed and tofu in bowls, top with warmed dashi broth seasoned with soy sauce and sake, and garnish with thin strips of lemon zest;
  • Seaweed can be prepared in tempura like other vegetables;
  • The Japanese also use it for decoration: they wrap thin strips around the tails of shrimps or around a packet of soba noodles to make pretty little bundles to be fried with the vegetables or fish.

Using seaweed to make delicious condiments

  • Mix equal parts table salt and seaweed powder;
  • Wakame or dulse can be simply grilled and ground into a powder to be added to the dish of your choice;
  • Boil several sheets of nori in ½ cup of water and cook over low heat until most of the water is absorbed, to make a thick puree. Add a little tamari, cook for a few more minutes and serve with rice or vegetables ,
  • Toast wakame in a 350°F (180°C) oven for 10 to 15 minutes. Allow to cool and grind into powder. Dry roast sesame seeds in a pan and grind them with the seaweed powder until 80% of the seeds are pulverized. The ratio of wakame to sesame seeds can vary from 1:1 to 1:5, depending on the intended use.

 Contraindications and allergies to algae

There are relatively few contraindications to the consumption of seaweed, except in the case of thyroid disorders or anticoagulant treatment. However, because of its high sodium and iodine content, seaweed should be consumed in moderation and as part of a varied and balanced diet.

Beware of excess iodine

Iodine is a component of thyroid hormones, which are necessary for the regulation of growth, development and metabolism. On the other hand, too high concentrations of iodine can cause problems with the functioning of the thyroid gland. Despite the relatively high amounts of iodine in nori, its usual consumption does not present a significant health risk. However, it is recommended that people who consume seaweed on a regular basis choose those with the lowest iodine content, such as sea lettuce, porphyry (Japanese nori) and dulse. One or two sheets of nori (equivalent to 8 to 15 sushi) are enough to meet daily iodine requirements.

Hijiki and arsenic

The Canadian Food Inspection Agency advises against the consumption of hijiki seaweed (a black, slightly bitter seaweed sold dried). The inorganic arsenic content of hijiki seaweed may exceed acceptable daily levels, even when consumed in small amounts. Of several seaweed samples analyzed, including dulse, porphyry and kelp, only the hijiki variety contained elevated levels of inorganic arsenic. Exposure to high levels of inorganic arsenic has been associated with gastrointestinal disorders, anemia and liver damage.

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Algae and anticoagulant treatments

Seaweed contains large amounts of vitamin K, which is necessary for blood clotting. People who take anticoagulant drugs (e.g. Coumadin®, Warfilone® and Sintrom®) should eat a diet in which the vitamin K content is relatively stable from day to day. For these people, seaweed should not be consumed as a main course (e.g. a sushi meal). People on anticoagulation therapy are advised to consult a dietitian-nutritionist or a physician to find out about food sources of vitamin K to ensure the most stable daily intake possible.

 History and anecdotes

The term “algae”, which appeared in 1551, comes from the Latin alga. There is no doubt that algae have been known and consumed by Homo sapiens since his appearance on the planet. It is even thought that his predecessor, Homo erectus, was already consuming them. These marine plants are part of the culinary traditions of coastal populations in China, Japan, Polynesia, Hawaii, the United Kingdom, Iceland and Siberia.

Seaweed and world gastronomy

Chinese texts dating from the 6th century BC mention varieties of seaweed with a taste fine enough to be on the menu of kings. In Japan, as early as the 13th century, 8 species were commonly consumed, a number that has now risen to 21. In the 10th century, dulse (or rhodymena palmate) was common enough in the Icelandic diet that its harvesting was regulated.

Seaweed is also an important part of Amerindian and Inuit culinary traditions. On the Arctic coast, seaweed has always been an important resource in times of famine. It is also known that the Inuit consumed the stomach contents of the whales they fished out, which consisted mainly of microscopic algae. In addition, the Amerindians harvested the eggs that the females of various species of fish laid on the kelp, and cooked the eggs and kelp together. This dish is highly prized by the Japanese, who pay a high price to import it from Canada or the United States.

Knowing the nutritional richness of seaweed, it is surprising that Europeans, excluding those of the North, and North Americans, have consumed them so little or not at all. For example, in Brittany, a country of sailors where 600 species have been recorded, there is only one traditional dish (a kind of flan) made from these plants. However, this situation is changing under the influence of Japanese cuisine, which is spreading throughout the world. Chefs in the East and West are competing to put them on the menu, with sushi being the most common example.

Seaweed cultivation

As early as the end of the 17th century, the Japanese began to cultivate certain species in the brackish waters of Tokyo Bay. Since then, seaweed farming has greatly expanded, with 90% of all commercially available seaweed being cultivated. The main producing countries are China, Japan and Korea. The simplest method is to install supports in the marine environment to which they cling, as is done for mussels. However, land-based culture in tanks filled with purified seawater is rapidly evolving. This method has recently been implemented in Nova Scotia. For the future, the industry is looking at the possibility of producing genetically modified varieties in a closed fermenter-type environment where all environmental factors are controlled.

Did you know? In the Prince of Wales Archipelago in southeast Alaska, there is a village named Sukkwan by the Haida-Kaiganis, the original inhabitants of the area. Sukkwan is a Tlingit word that literally means “village on the beautiful underwater grass,” referring to the edible seaweed that grows in the coastal waters.

Algae, ecology and environment

In France, researchers at the Centre National de Recherche Scientifique have been conducting research for several years into what is known as the “vaccination” of crop plants by seaweed. The starting hypothesis is that seaweed has molecules that provoke an immune response in plants and enable them to protect themselves against diseases. These molecules cause a series of reactions in the plant cells, such as the formation of true plant antibiotics, called “phytoalexins”, or defence proteins (Pathogenesis related proteins).

As with vertebrates, “plant vaccination” requires only very small amounts of the active agent. In fact, once a certain threshold is exceeded, the effect is reduced. Protection lasts for about 6-8 weeks, after which treatment should be repeated if necessary. However, it is essential that the treatment is applied before the onset of the disease. This type of prophylaxis does not completely eliminate the need for fungicides (fungicide agents), but it does greatly reduce the amount required.

Seaweed has long been used in organic farming to stimulate plant growth and protect against disease. Potato growers in coastal areas used to put seaweed in the planting furrows. Later, they learned to make a mash by soaking them in water. After being filtered, the liquid manure was applied to the plants. Today, the practice is widespread in organic agriculture, with the difference that industrially prepared extracts are usually used. These extracts, whether based on algae or terrestrial plants, are a natural alternative to synthetic pesticides and controversial GMOs.