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Algae – nutritious lettuce from the sea

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Algae and seaweed (which is actually a kind of algae) have long been key components of many regional coastal diets, particularly in Asia. In recent years, sushi, seaweed, and algae have become popular and increasingly mainstream food items. ProVeg presents a selection of the different types of algae, along with their health benefits.

Different kinds of algae

Algae are divided into microalgae and macroalgae, based on their size. While microalgae sometimes only measure a few micrometers, macroalgae are visible to the naked eye and can measure up to several meters. In most cases, macro algae are used as an ingredient in dishes, while microalgae tend to be used more often in food supplements or food additives.1

Algae are classified by their colors: brown algae such as wakame, red algae such as dulse, and green algae such as spongeweed.The term blue-green algae is also used, although these ‘algae’ are in fact cyanobacteria and therefore not biologically related to other algae. Marine algae, including most red and brown algae, are found in saltwater, while the majority of green algae thrives in freshwater. Cyanobacteria can be found in both fresh and saltwater algae, depending on the species.2

Category of algae Common representative Usage examples
brown algae (macroalgae) wakame (seaweed) Wakame lends a spicy flavor to miso soup3
kombu (seaweed) The algae Laminaria japonica is more commonly called kombu or Japanese kelp. It can be served by itself or in a salad.4 5 6
hijiki Hijki can be used as a side dish or in soups and wok dishes.7
arame Arame contains large amounts of iodine and has a sweet taste.8
thongweed Thongweed can be used in a variety of ways, including as a salad or as a replacement for spaghetti. It has a similar taste to beans.9
knotted kelp Knotted kelp is mainly used in food supplements but is also suitable for soups.
Laminaria saccharina Laminaria saccharina is cultivated and sold on Germany’s northernmost island of Sylt.10
red algae (macroalgae) dulse The slightly nutty taste adds a distinctive flavour to many dishes.11
nori This algae is mainly used as the wrap in sushi rolls.
carrageen moss (Irish moss) Mashed with water, dried carragheen moss can be used as vegan thickener since it consists mostly of carrageenan.12 13
green algae Ulva (sea lettuce) (macroalgae) Ulva is a popular choice for use in seafood salads in France, and can also be used in soups.14
The green algae chlorella is cultivated in fresh water and is available as a food supplement.15
Schizochytrium sp. The microalgae Schizochytrium sp. is high in the omega-3 fatty acids DHA and EPA and is often added to oils.16
Ulkenia sp.
Ulkenia sp. is also high in omega-3 fatty acids and is used as an ingredient in baked goods.17
(often called blue-green algae, although they are not truly algae)
spirulina Spirulina is most widely consumed as a food supplement, in the form of powder or tablets.18
Aphanizomenon flos-aquae (AFA algae) AFA is also consumed as as food supplement.19 20

Kelp and seaweed – different names for brown algae

Kelp refers to several kinds of brown algae, which often form ‘forests’ on stony parts of the seabed. Kelp grows in cold temperatures. For example, the subspecies laminaria can be found in the Northern Atlantic.21 Seaweed is often used as an umbrella term that includes brown algae such as wakame and kombu.22 23

Nutrient composition of algae

Algae have the ability to absorb minerals and trace elements from the water, and are thus high in iron and calcium, for instance. In addition, many algae are rich in vitamins such as vitamin C and B12, and also contain large amounts of beta-carotene. They are quite high in protein, while their fat content is minimal. The nutrient profiles of algae vary, depending on the type of algae as well as environmental conditions, time of harvest, and the method of preservation.24

Nutrient levels are also dependent on water quality, regardless of whether the algae is harvested in aquacultures, salt water, or fresh water.25 However, since algae is usually served in small portions, fruit and vegetables are generally better sources of vitamins and minerals.26 27

Nutrient Quantity Especially in the following species
calcium 30–575 mg* knotted kelp, kombu, sea lettuce, carrageen moss
iron 4–45 mg* kombu, sea lettuce, thongweed
iodine 1.3–98 mg* kombu, arame, wakame, hijiki
vitamin C 7.5–175 mg*
(dried algae)
wakame, nori, sea lettuce
protein Up to 47% of dry weight but varies substantially spirulina, nori
carbohydrates 4–15 g* knotted kelp, thongweed, dulse
fiber 3–10 g* knotted kelp, thongweed
fat Up to 2% of dry weight All algae are low in fat and the differences in fat content between different species is miniscule.
omega-3 fatty acids 7–44% of total fat wakame, dulse

*per 100 g of algae28

Plant-based nutrients

A plant-based diet can provide an ample supply of all the nutrients needed for optimal health. But whether you’re a vegetarian, vegan, or meat-eater, a healthy body requires a balanced and varied diet that includes all the necessary nutrients.

Algae is rich in iodine

Algae is considered to be a good source of iodine and can replace iodized table salt. However, special caution is required as the iodine content can vary greatly between different species of algae, as well as within a species. It is therefore very difficult to make reliable statements about the iodine content of algae.29

The National Institutes of Health recommends a daily consumption of 0.15 mg of iodine for adults.30 Due to potentially severe side effects when consuming too much iodine, the German Federal Institute for Risk Assessment holds the position that algae products which contain more than 20 mg per kg are not legally saleable.31 Algae products with a level of iodine between 10 and 20 mg per kg should carry a warning label since excessive consumption can lead to thyroid problems (hypothyroidism/hyperthyroidism).

Moreover, algae products should provide information about the level of iodine they contain, the recommended maximum daily dose, and the correct preparation. Only then, can consumers get an idea of how much iodine they are consuming and avoid overconsumption. Algae such as arame, kombu, wakame or hijiki are especially high in iodine. When these points are taken into account, algae can be a good source of iodine and part of a healthy meal plan.32 33

Omega-3 fatty acids: algae provide DHA and EPA

In June 2003, the European Commission decided that, under certain conditions, the oil of the microalgae Schizochytrium sp., which is high in DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid), may be used as a food ingredient.34 35 Another DHA-rich microalgae oil, extracted from the microalgae Ulkenia sp., was approved as an additive for certain food groups in 2009.36

Consuming these algae is a good way to incorporate polyunsaturated omega-3 fatty acids into one’s diet. This is especially true for vegans and vegetarians. Algae-based omega-3 fatty acids do not differ from the fatty acids found in coldwater fish, since consuming algae is how fish absorb and accumulate these fatty acids in the first place. Besides being used as food additives, DHA and EPA are also sold as food supplements.37

Preventing cancer with algae

Alginates are the cell walls of wakame and are classified as dietary fibre. They have gel-forming properties and can thus enhance the feeling of satiety. Additionally, alginates inhibit certain enzymes so that already-bound carcinogens stay in the intestine, are not reactivated, and are instead secreted. As a consequence, the consumption of brown algae can help to prevent cancer. On the other hand, calcium also binds to alginates, and thus becomes unavailable to the body. However, within the context of a balanced, nutritious diet, this does not present a problem.38 39

The polysaccharide Fucoidan is found mainly in wakame and kombu, and is a by-product of the extraction of alginates. For some years now, there have been research approaches which suggest that fucoidan has the potential to be used as a pharmaceutical product. Supposedly, it has a positive impact on the immune system and on tumours and viruses. However, the cause of these effects is still unclear, as is the question as to whether they have any significant impact on the human body. Further studies are required to clarify these issues.40 41 42

Production of algae

Algae is harvested directly from the sea, as well as cultivated in marine farms. In Asia, the harvest of algae has a long history. However, macroalgae is also harvested in several European regions, with France being the biggest algae producer in Europe. Worldwide, China claims first place, followed by Indonesia, the Philippines, South Korea, and Japan. Other countries where algae is harvested include Ireland, Great Britain, and Norway.43 44 The microalgae spirulina is especially prevalent on the world’s algae farms: for example in the USA, Thailand, Taiwan, Chile, Spain, Australia, and China.45

Alginic acid, agar-agar and carrageenan: algae in the food industry

The food additives alginic acid, agar-agar, and carrageenan are extracted from the cell walls of algae.46 47 For the extraction of alginic acid and alginates (E400 to E405) brown algae is used. These additives are used as stabilizers and thickening agents in foods such as ice cream, salad dressing, and pudding.48 Agar-agar is extracted from red algae and is used as a thickening agent (E406).49 Red algae are also used for the production of carrageenan (E407), a gelatin-free additive that is used as a stabiliser and gelling agent.50

Carotenoids extracted from algae

The food, beverages, and supplement industries use several carotenoids derived from algae – as a source of provitamin A and as food colouring agents. Beta carotene and astaxanthin, for example, are extracted from micro algae and sold mainly as food supplements, as well as being used as a colouring agent for desserts, ice cream, and beverages.51 52

Risk: microalgae in food

There is an increasing number of products which are fortified with certain kinds of algae – for example, smoothies with added chlorella and spirulina.53 Aphanizomenon flos-aquae (AFA), a type of freshwater algae harvested mainly from mountain lakes in Oregon (USA), belongs to the group of cyanobacteria and is available as a powder and as pills.54 These algae are remarkably low in iodine, while providing high levels of protein, vitamins, and other minerals. Since the daily consumption of this product is limited to a few grams, the amount of nutrients which can be absorbed by the body is rather low in comparison with other foods. The German Federal Institute for Risk Assessment points out that there is no scientific proof that these algae products come with any health benefits or have a positive effect on diseases.55

Strictly speaking, there is the problem of certain types of cyanobacteria, such as AFA algae, accumulating toxic substances (for example heavy metals), as well as producing such substances themselves. Therefore, it cannot be ruled out that these products have a negative impact on health.56 57 58 AFA algae are not cultivated, but harvested from the sea. Since they often grow next to toxic algae, AFA algae can also be contaminated with their toxins.59

Tips for cooking: cooking and storage

Algae is often sold dried and can be stored almost indefinitely. After washing them, they are soaked in water to let some of the iodine seep into the water .Rinsing the soaked algae further reduces the iodine content. Nori, however, is an exception and does not have to be soaked.
To give soups and stews a hearty note, small pieces of dried algae, which may be roasted beforehand, will suffice. Their glutamic acid is a natural flavour enhancer. Ground to a powder and stored in a jar, this condiment is almost non-perishable.

  • The soaking time for legumes such as lentils and beans can be accelerated by adding brown algae. The glutamic acid makes the legumes softer and shortens the cooking time.60 61 62
  • There is no culinary limit: fried, stewed, added to a soup, or pickled – the variety of algae makes cooking more fun.
  • There are also some fish alternatives made from algae.

Recipe: cooking with algae

Nori is especially popular when it comes to cooking with algae. Thanks to nori, the vegan versions of fish cakes, herring salad, and tuna sandwich are convincing alternatives.


Fresh or dried algae can broaden one’s diet and are considered a good source of nutrients. However, for health reasons, you should note the following:

  • Choose products that are properly labelled and provide information about the level of iodine and the correct cooking method.
  • Note the maximum recommended daily dose, for example, no more than one teaspoon of nori flakes per day.
  • Avoid dubious algae supplements.


ProVeg has created a recipe collection with the most delicious dishes. In our collection, you can find plant-based inspirations for breakfast, lunch or dinner. What do you want to cook today?


Last updated: 21.08.2020

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