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For other uses, see Nori (disambiguation).

Nori (海苔?) is the Japanese name for edible seaweed species of the red algae genus Porphyra, including P. yezoensis and P. tenera. Nori is familiar in the United States and other countries as an ingredient of sushi, being referred to as "nori" (as the Japanese do) or simply as seaweed. Finished products are made by a shredding and rack-drying process that resembles papermaking.

Porphyra is also called laver in Wales and other English-speaking countries.[1]


Cakes and Food Made of Seaweed by Kubo Shunman, 19th century

Originally, the term nori was generic and referred to seaweeds including hijiki.[2] One of the oldest descriptions of nori is dated to around the 8th century. In the Taihō Code enacted in 701, nori was already included in the form of taxation.[3] Local people have been described as drying nori in Hitachi Province Fudoki (721–721), and nori was harvested in Izumo Province Fudoki (713–733), showing that nori was used as food from ancient times.[4] In Utsubo Monogatari, written around 987, nori was recognized as a common food. The original nori was formed as a paste,[citation needed] and the sheet form was invented in Asakusa, Edo (contemporary Tokyo), in the Edo period through the method of Japanese paper-making.[5]

The word "nori" first appeared in an English-language publication in C. P. Thunberg's Trav., published in 1796.[6] It was used in conjugation as "Awa nori", probably referring to what is now called aonori.[6]

The Japanese nori industry was in decline after WWII, when Japan was in need of all food which could be produced. The decline was due to a lack of understanding of the plant's three stage life cycle so that local people did not understand why traditional cultivation methods were not effective. The industry was rescued by knowledge deriving from the work of British phycologist, Kathleen Mary Drew-Baker who had been researching the organism porphyria umbilicalis, which grew in the seas around Wales and was harvested for food, as in Japan. Her work was discovered by Japanese scientists who applied it to artificial methods of seeding and growing the plants, rescuing the industry. Kathleen Baker was hailed as the 'Mother of the Sea' in Japan and a statue erected in her memory.

The word nori started to be used widely in the United States, and the product (imported in dry form from Japan) became widely available at natural food stores and Asian-American grocery stores in the 1960s due to the macrobiotic movement, and in the 1970s with the increase of sushi bars and Japanese restaurants.[citation needed]

In one study by Jan-Hendrik Hehemann, subjects of Japanese descent have been shown to be able to digest the polysaccharide of the seaweed, after gut microbes developed the enzyme from marine bacteria. Gut microbes from the North American subjects lacked these enzymes.[7]


Production and processing of nori is an advanced form of agriculture. The biology of Porphyra, although complicated, is well understood, and this knowledge is used to control the production process. Farming takes place in the sea where the Porphyra plants grow attached to nets suspended at the sea surface and where the farmers operate from boats. The plants grow rapidly, requiring about 45 days from "seeding" until the first harvest. Multiple harvests can be taken from a single seeding, typically at about ten-day intervals. Harvesting is accomplished using mechanical harvesters of a variety of configurations. Processing of raw product is mostly accomplished by highly automated machines that accurately duplicate traditional manual processing steps, but with much improved efficiency and consistency. The final product is a paper-thin, black, dried sheet of approximately 18 cm × 20 cm (7 in × 8 in) and 3 grams (0.11 oz) in weight.

Several grades of nori are available in the United States. The most common, and least expensive, grades are imported from China, costing about six cents per sheet. At the high end, ranging up to 90 cents per sheet, are "delicate shin-nori" (nori from the first of the year's several harvests) cultivated in Ariake Sea, off the island of Kyushu in Japan".[8]

In Japan, over 600 square kilometres (230 sq mi) of Japanese coastal waters are given to producing 350,000 tonnes (340,000 long tons) of nori, worth over a billion dollars. China produces about a third of this amount.[9]


Negitoro gunkanmaki (葱トロ軍艦巻き)

Nori is commonly used as a wrap for sushi and onigiri. It is also a garnish or flavoring in noodle preparations and soups. It is most typically toasted prior to consumption (yaki-nori). A common secondary product is toasted and flavored nori (ajitsuke-nori), in which a flavoring mixture (variable, but typically soy sauce, sugar, sake, mirin, and seasonings) is applied in combination with the toasting process.[10] It is also eaten by making it into a soy sauce-flavored paste, nori no tsukudani (海苔の佃煮).

Nori is sometimes used as a form of food decoration.

A related product, prepared from the unrelated green algae Monostroma and Enteromorpha, is called aonori (青海苔 literally blue/green nori) and is used like herbs on everyday meals, such as okonomiyaki and yakisoba.

Since nori sheets easily absorb water from the air and degrade, a desiccant is indispensable when storing it for any significant time.


Seaweed, laver, raw
Nutritional value per 100 g (3.5 oz)
Energy 35 kcal (150 kJ)
5.11 g
Dietary fiber 0.3 g
0.28 g
5.81 g
Vitamin A equiv.
260 μg
Thiamine (B1)
0.098 mg
Riboflavin (B2)
0.446 mg
Niacin (B3)
1.470 mg
Folate (B9)
146 μg
Vitamin B12
0.000 μg
Vitamin C
39.0 mg
Vitamin D
0 μg
Vitamin E
1.00 mg
Vitamin K
4.0 μg
Trace metals
70 mg
1.80 mg
2 mg
58 mg
356 mg
48 mg
1.05 mg
Other constituents
Water 85.03 g
Percentages are roughly approximated using US recommendations for adults.

Porphyra yezoensis has been found to contain sufficient vitamin B12 to prevent vitamin B12 deficiency in rats.[11] Though Nori has long been considered to be an important source of vitamin B12 for vegans, its vitamin B12 may actually not be biologically available to humans. It may contain cobalamin analogues which block absorption of B12.[12][13] However, recent studies have shown otherwise, that Nori (Porphyra yezoensis) contains a significant amount of bioactive vitamin B12, not the inactive analogues.[14]


There is controversy in plant-based vegan communities regarding the composition of nori. Nori (the sea vegetable), often used to make sushi, grows as a lettuce in the ocean. The nets used in the harvesting process of nori are believed to scoop up small fish. Following this, seaweed, shrimp, crabs, snails, barnacles and small fish are ground together and made into nori sheets. The industry is so large that it often does not take the time to remove the sea animals. Japan is the world’s largest nori supplier. However, Nagata and Yamamoto, two suppliers of nori, claim that animal contamination is minimal.[15] Vegan communities are divided among this issue and often seek kosher certified kibbutz who offer fish free nori to create vegetable sushi dishes. Additionally, mechanical seaweed harvesting is considered highly unethical by some environmentalists because of the over harvesting taking place in the earth’s oceans. Over Harvesting takes away from the ecology of an ocean, putting all sea life and marine animal lives at risk. Seaweed plays a vital role in the marine ecology. Nitrogen is removed from the sea by seaweed and seaweed removes carbon dioxide from the sea.[16] It is argued that mechanical harvesting of seaweed may never be sustainable. For example, the mechanical harvesting on the Norwegian coast is so extensive, that if all seaweed harvesting procedures followed their practices, many fish and other marine life would be dead. In one square metre of the oceans floor, there is up to 100,000 organisms living there, potentially being harvested with the seaweed. With 90% of fish already being taken out of the ocean due to overfishing, over harvesting practices are of significant concern for the environment. Individuals on a plant-based may choose not to consume nori for ethical reasons, however it is unfortunate as seaweed provides omega-3s, iodine, calcium and magnesium for vegans who may otherwise not get these nutrients.[17] Not only can nori contain small amounts of fish and other marine life, but it catches and filters a lot of pollution. Seaweed does for the ocean what plants do for our air, therefore, heavy metals, toxic materials and other pollution that is dumped into ocean water has a strong possibility of being harvested and sold in nori and seaweed products.[18]

See also[edit]


  1. ^ "Nori". Merriam-Webster. Retrieved 25 March 2013. 
  2. ^ Kodansha encyclopedia of Japan 6. Kōdansha. 1983. p. 37. ISBN 0-87011-620-7. The word nori is used in Japan both as a general term for seaweed and as a name for a species of red algae (Porphyra tenera) that is commonly used as a foodstuff and is also known as asakusa- nori. 
  3. ^ Nisizawa, Kazutosi; Noda, Hiroyuki; Kikuchi, Ryo; Watanabe, Tadaharu (September 1987). "The main seaweed foods in Japan". Hydrobiologia. 151-152 (1): 5. doi:10.1007/BF00046102. In the Law of Taiho (AD 701) which was established by the Emperor at that time, marine algae such as Laminaria, Undaria and its sporophyll, Porphyra and Gelidium are included among marine products which were paid to the Court as tax. 
  4. ^ Hiroshi, Terayama (2003). 和漢古典植物考 (Japanese and Chinese Classical Botany). asaka Shobō. p. 588. There is a description "local people were drying nori" in Hitachi Province Fudoki (721–721), and also there is a description "nori was harvested" in Izumo Province Fudoki (713–733). These show nori was used as food from ancient times. 
  5. ^ Shimbo, Hiroko (2001). The Japanese kitchen: 250 recipes in a traditional spirit. Harvard Common Press. p. 128. ISBN 1-55832-177-2. 
  6. ^ a b "Nori". Oxford English Dictionary, Third Edition. September 2012. Retrieved 25 March 2013. 
  7. ^ Hehemann, Jan-Hendrik; Correc, Gaëlle; Barbeyron, Tristan; Helbert, William; Czjzek, Mirjam; Michel, Gurvan (April 2010). "Transfer of carbohydrate-active enzymes from marine bacteria to Japanese gut microbiota". Nature 464 (7290): 908–12. doi:10.1038/nature08937. PMID 20376150. 
  8. ^ Goode, J.J. (January 9, 2008). "Nori Steps Away From the Sushi". The New York Times. Retrieved 25 March 2013. 
  9. ^ Thomas, David (2002). Seaweeds. London, England: Natural History Museum. ISBN 0-565-09175-1. [page needed]
  10. ^ Shurtleff, William; Aoyagi, Akiko (1975). The Book of Tofu: Food for Mankind, Volume 1. Soyinfo Center. p. 327. ISBN 0394734319. 
  11. ^ Takenaka, S.; Sugiyama, S.; Ebara, S.; Miyamoto, E.; Abe, K.; Tamura, Y.; Watanabe, F.; Tsuyama, S.; Nakano, Y. (June 2001). "Feeding dried purple laver (nori) to vitamin B12 deficient rats significantly improves vitamin B12 status". British Journal of Nutrition 85 (6): 699–703. doi:10.1079/BJN2001352. PMID 11430774. 
  12. ^ Watanabe, Fumio (November 2007). "Vitamin B12 Sources and Bioavailability". Experimental Biology and Medicine 232 (10): 1266–74. doi:10.3181/0703-MR-67. PMID 17959839. Retrieved 25 March 2013. 
  13. ^ Allen, Lindsay H. The United Nations University, Food and Nutrition Bulletin, vol. 29, no. 2. "Causes of vitamin B12 and folate deficiency". Accessed June 30, 2013.
  14. ^ "Characterization of a vitamin B12 compound in the edible purple laver, Porphyra yezoensis" 64 (12). December 2000. pp. 2712–5. PMID 11210144. 
  15. ^ Saffron. "Fish In Your Nori". Retrieved January 29, 2015. 
  16. ^ "Ban Seaweed Harvesting". YouTube. 
  17. ^ McLees.  Missing or empty |title= (help)
  18. ^ Patenaude.  Missing or empty |title= (help)

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