Sushi made them famous: the nori seaweed. Here’s why they’re trending, how they’re grown and what’s behind their reputation as a “superfood”.
Nori seaweed – or just nori for short – is one of the best-known edible seaweeds. As nori sheets, they are an essential part of sushi. But you can also use them for salads and soups – as well as for various Japanese recipes. In addition, there are many cosmetic products with algae, for example masks and creams.
According to the magazine GEO, 400,000 tons of nori seaweed are harvested every year. In total, the harvest of edible algae is over nine million tons. They come primarily from Japan, China, the Philippines and Korea – but algae are also cultivated in Brittany and California. Algae farms are a good alternative to traditional farms, especially in Japan, because there is a lack of agricultural land.
Nori seaweed belongs to the red algae, a class of algae that consists of over 4,000 species and is predominantly found in the sea. Nori algae does not exist in our seas, but there are also close relatives in the North Sea, on Heligoland and on the coasts of Great Britain, according to rbb. (link to audio file)
In addition to nori algae, there are many other edible algae such as green algae. They include, for example, ulva, the so-called sea lettuce – it is considered a delicacy in France. There is also sugar kelp and brown algae like wakame, which are part of the Japanese miso soup. All of these species belong to the macroalgae, i.e. large-leaved algae with many cells. In addition, there are microalgae such as spirulina algae and chlorella, which are often marketed as dietary supplements.
Nutritional values and ingredients of nori seaweed
Nori seaweed is particularly popular with vegans – because it contains vitamin B12, which is otherwise found almost exclusively in animal products. As the German Society for Nutrition (DGE) explains, it has not yet been clarified whether the vitamin in nori algae has a high bioavailability. That means it’s unclear how much of the vitamin in the algae our bodies can utilize. A Finnish study speaks in favor of algae as a source of vitamins: As part of the study, a group of vegans had consumed nori algae and/or chlorella over a longer period of time – they had twice the B12 content in their blood as vegans control group. In addition to vitamin B12, nori seaweed also contains B vitamins such as folic acid and beta-carotene.
On seaweed products you will often see warnings about the high iodine content of seaweed. Iodine is a trace element that our body needs, but which can lead to thyroid problems in excessive amounts. However, according to the Federal Center for Nutrition, nori algae have a rather low and therefore unproblematic iodine content – unlike their relatives, the brown algae. Soaking and rinsing the seaweed in water before eating can further reduce the iodine content.
Note: People with thyroid problems should avoid eating algae or consult their doctor beforehand.
This is how nori seaweed is grown
Nori seaweed is preferred in tanks. In it, the spores are stored on oyster shells for about five months. So-called seeding nets are then hung in the tank and the water is kept moving for 20 to 60 minutes. This stirs up the spores and causes them to get stuck in the web. The farmers then place the nets covered with spores in the sea.
In the first month after sowing, the algae only grow about a centimeter. Then their growth accelerates massively, they can grow up to 15 centimeters longer within two weeks. After fifty days they have reached a length of 15 to 20 centimeters. After harvesting, the nori seaweed is immediately dried and cut into leaves.
How sustainable is nori seaweed?
The nori seaweed that we buy in the supermarket or are served in the restaurant usually comes from Southeast Asia. They usually have a long transport route behind them.
It is best to use a product with an organic seal. According to the Federal Center for Nutrition, the EU organic regulation requires that the organic algae come from bodies of water with a high ecological quality and are managed sustainably. The organic association Naturland has, among other things, even stricter requirements for water quality – social standards are also taken into account. You can find nori algae with an organic seal in health food stores.
According to GEO, algae have a positive effect on the climate: they remove three times as much carbon dioxide from the air as crops – and can thus bind many greenhouse gases. However, they are not without controversy because, according to the spectrum, too many algae can lead to an algal bloom: This describes the mass proliferation of algae in nutrient-rich waters. This algae then dies, sinks to the bottom and is decomposed by bacteria. This is an aerobic process, which means that the bacteria use oxygen. As a result, numerous other creatures that are dependent on the oxygen in the water die. The body of water becomes a dead zone. In addition, gases can form under the algae carpets that are toxic and harmful to the climate. Some algae also produce toxins themselves.
How the cultivation of edible algae affects the climate, positively and negatively, has not yet been researched much. If it is operated sustainably, algae farming can produce regionally grown, climate-friendly and nutrient-rich food. Algae are also being discussed as fuel for cars, as a raw material for clothing and as packaging material.
