Seaweed: Healthy Vegetables From The Ocean

Seaweed such as nori, wakame, or kelp has long since arrived in European kitchens. They give food a pleasant sea aroma and also contain plenty of minerals, omega-3 fatty acids, and fiber.

Seaweed and its use

In Europe, we usually only know seaweed wrapped around sushi, but in Asian countries, they are also served raw in salads or steamed as vegetables in all sorts of variations. Archaeological finds show that algae have enriched human nutrition for thousands of years. And not only in Asian countries, as one might assume, but also in Chile, North America, and Ireland.

Recently, seaweed has seen a real boom in Europe. They are particularly popular in the cosmetics sector: seaweed is said to be good for the skin and hair and is therefore increasingly being used for cosmetic products and wellness treatments. In the kitchen, they are used more and more frequently as condiments, soups, salads, or, of course, as sushi casings.

Seaweed in all colors and sizes

A distinction is made between microalgae, such as chlorella, which are microscopically small, and macroalgae, such as wakame, nori, kombu, and co. The latter can sometimes be several meters long. Algae can also be roughly classified according to their color: a distinction is made between red algae, brown algae, green algae, and blue-green algae. The red algae include, for example, dulse and purple kelp (also called nori), the brown algae include wakame and hijiki, and the green algae include sea lettuce. Some representatives of the red, brown, and green algae are also referred to as seaweed.

Exactly how many species of algae exist has not been clarified to this day – in any case, there are thousands of them. Some estimates are even in the millions. It is difficult to give an exact number because the demarcation from other organisms is not entirely clear. Simply put, algae are organisms that live underwater and carry out photosynthesis. However, some bacteria can also carry out photosynthesis. Spirulina, for example, actually belongs to the cyanobacteria but is usually also counted among the microalgae.

The nutritional values, vitamins, and minerals of seaweed

Although seaweed is only eaten in small amounts (e.g. around 10 grams of dried seaweed per person in a seaweed salad), they do a good job of covering vitamin and mineral needs. Red seaweed includes dulse and purple kelp (nori), while brown seaweed includes wakame, hijiki, kelp, kombu, kelp (sea spaghetti), and arame. However, the values ​​can vary greatly depending on the specific type of algae, region, and season.

The nutritional values ​​of seaweed

Seaweed is low in fat, low in calories (about 300 kcal per 100g), and high in fiber. Their fiber content ranges from 23.5 to 64 percent of their dry weight. In a Korean study, the high fiber content of seaweed had a positive effect on blood sugar levels in type 2 diabetes patients.

The vitamins of seaweed

Seaweed contains relevant amounts of beta-carotene, B vitamins, vitamin C and folic acid. Seaweed also contains vitamin B12. However, these could be so-called vitamin B12 analogs – distinguishing these analogs from real vitamin B12 is not easy and has often led to misunderstandings.

Vitamin B12 analogs and vitamin B12 merely have a similar structure and bind to the same transport molecules but have no vitamin effect. Since the analogs occupy the transport molecules of the actual vitamin B12, it is less well absorbed. Under certain circumstances, an existing vitamin B12 deficiency can even be aggravated.

A study on rats with vitamin B12 deficiency showed that the vitamin B12 in dried nori seaweed is at least partly real vitamin B12. However, it comes from microorganisms on the algae and not from the algae themselves, which is why the value can vary greatly. So you should never rely on seaweed as a source of vitamin B12.

The minerals of seaweed

Seaweed appears to be rich in minerals as it contains large amounts of minerals per 100g. However, since you only eat a small amount of it (approx. 10 g), the amounts of minerals absorbed with algae shrink significantly again. Hijiki, for example, is particularly rich in calcium with 1170 mg and sea lettuce with around 1830 mg per 100 g. With a consumption of 10 g, however, only 117 and 183 mg of calcium remain, which still accounts for 10 to 20 percent with a daily requirement of 1000 mg.

High iron levels can also be found in hijiki (4.7 mg per 10 g). In sea lettuce (1.4 mg) and dulse (1.3 mg), the value is no longer as high. The iron requirement of an adult is 10 to 15 mg.

The iodine content of seaweed

Algae are very good sources of iodine. The iodine content varies depending on the species. Kelp in particular stands out with up to 5307 µg/g. The daily requirement for iodine is 200 µg, and the maximum tolerable amount is 500 µg iodine per day. Kelp should therefore only be consumed in tiny amounts, as just 5 g of kelp can provide more than 250 µg of iodine, i.e. more than the daily requirement.

An overdose of iodine can lead to an overactive or underactive thyroid. Regular consumption of large amounts of algae, as is common in Japan, for example, is also associated with an increased risk of thyroid cancer. On average, the Japanese eat 13.5 grams of seaweed per day. However, z. For example, a 2012 study found an increased risk of thyroid cancer only in postmenopausal women (not in premenopausal women) and only if they ate seaweed daily (compared to women who only ate seaweed twice a week).

Therefore, if you eat a dish with seaweed twice a week, most likely you do not have to fear any negative consequences. On the contrary. Your thyroid will be happy about the good iodine supply.

Below you will find a comparison of the iodine content of some types of algae. As with the nutritional values, the information on the iodine content can vary greatly within the species and depending on the region of origin. Nori has a comparatively low iodine content, while dulse is in the middle. Bear in mind that this is the amount of iodine per gram, not – as usual – per 100 g:

  • Arame: 586 to 714 µg/g
  • Dulse: 44 to 72 µg/g
  • Hijiki: 391 to 629 µg/g
  • Kelp: 240 to 5307 µg/g
  • Sea lettuce: 48 to 240 µg/g
  • Nori (purple kelp): 16 to 45 µg/g
  • Wakame: 66 to 1571 µg/g

Reduce the iodine content of seaweed

Since iodine is water-soluble, a large part of the iodine content is lost during soaking and cooking (14 to 75 percent) – if you pour away the soaking or cooking water. In Dulse, for example, soaking for one hour reduced the iodine content by about 15 percent. Soaking had the greatest impact on a specific kelp species, the winged wrack ( Alaria esculenta ). Within an hour, the iodine content fell by more than half (from 599 µg to 228 µg/g). A longer soaking time of up to 24 hours had no further effect on the iodine content of either type of algae. So the ideal soaking time to reduce the iodine content is one hour.

Cooking at 100 degrees for 20 minutes resulted in a further average iodine reduction of 20 percent for dulse and a 27 percent reduction for kelp. Since the iodine is then also in the cooking water here, it must of course be poured away.

Seaweed during pregnancy

In some places, pregnant women are advised to supplement with a daily iodine diet in addition to a balanced diet. At the same time, it is not recommended to eat seaweed during pregnancy, as it could contain too much iodine. However, iodine should only be supplemented if a deficiency has been detected (in the urine). And with algae, in particular, an iodine deficiency can be compensated for very easily.

If you don’t have a thyroid disorder, an occasional high iodine intake doesn’t matter – as long as you don’t consume large amounts of it on a regular basis. For example, Food Standards Australia New Zealand advises pregnant and breastfeeding women not to eat seaweed products more than once a week. If too much iodine is ingested, the body can easily excrete it again on the other low-iodine days. This recommendation also applies to breastfeeding women and children.

Seaweed contains omega-3 fatty acids

In order to get enough omega-3 fatty acids in the diet, the consumption of fish is generally recommended. But fish do not produce the fatty acids themselves – they absorb them from algae and accumulate them in their meat.

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are the two most well-known long-chain omega-3 fatty acids. Both are found in seaweed: Dulse provides e.g. E.g. around 8.5 mg and Wakame 2.9 mg EPA per gram. Algae of the genus Sargassum nations, to which Hijiki belongs, also contain around 1 mg DHA per gram. The optimal omega-3-omega-6 ratio is generally found to be 4:1 to 1:1 indicated. In the case of seaweed, it is around 1:1 and can therefore be rated as very good.

The daily requirement of EPA and DHA together is often given as 250 to 300 mg. However, depending on the state of health and the ratio of omega-3 and omega-6 fatty acids consumed, the daily requirement is much higher. If chronic diseases are present, 1000 mg EPA and DHA per day are often recommended. With just a few grams of algae per day, you will not be able to consume sufficient amounts of omega-3 fatty acids.

However, the seaweed is used to make an omega-3-rich seaweed oil that is used in vegan dietary supplements. The preparations contain significantly higher amounts of omega-3 fatty acids than you could get from eating algae. We recommend the omega-3 capsules made from algae oil of effective nature, which provide 800 mg DHA and 300 mg EPA (Omega-3 forte).

Nori and Wakame against breast cancer

Since nori has been shown to have anti-cancer effects in cell and animal studies, and since nori is eaten extensively in Korea, researchers investigated whether this dietary habit could have an impact on the Korean population’s risk of breast cancer. The nori consumption of 362 women served as the data basis. Statistical analysis revealed that the more women ate nori seaweed, the lower their breast cancer risk.

The same analysis was done for Wakame, but no association with breast cancer risk was found. In contrast, wakame extract showed growth-inhibiting effects in cell and animal studies in existing breast cancer and also in eight other human cancer cell lines, including lung cancer, colon cancer, uterine cancer, skin cancer, and liver cancer. The reason for this effect is probably the carotenoid fucoxanthin contained in Wakame, which has an anti-cancer effect. Fucoxanthin is also found in other brown algae, such as B. Hijiki and Kelp, before.

Seaweed in neurodegenerative diseases

Researchers suspect that seaweed can also counteract inflammation of nerve tissue in the central nervous system through its anti-inflammatory and antioxidant effects. Inflammation in this area of ​​the body is called neuroinflammation. It is considered an important contributory cause of Alzheimer’s and diseases such as Parkinson’s and multiple sclerosis. Clinical studies that could confirm this assumption have not yet been performed.

However, epidemiological studies suggest that seaweed consumption could reduce the risk of neurodegenerative diseases, such as Alzheimer’s. Studies have compared the Western diet to the Japanese diet and the incidence of these diseases. In Japan, where more seaweed is eaten, neurodegenerative diseases are less common than in western countries. Of course, other differences in diet were also taken into account. However, cell and animal studies suggest that seaweed contributes at least in part to the lower risk.

The heavy metal contamination of seaweed

While algae are generally considered healthy in Asian countries and are often eaten every day, people in Europe are more critical due to possible pollution. Researchers studied the heavy metal contamination of Asian and European seaweed.

Cadmium in seaweed

Many foods store cadmium, e.g. B. sunflower seeds, salads, apples, tomatoes, potatoes, and algae. Cadmium is said to be able to lead to kidney dysfunction and is only slowly eliminated from the body. The cadmium content in Asian algae was 0.44 mg/kg in a Spanish study, and that of European algae was 0.10 mg/kg ( 44 ). Below you will find the cadmium levels of other foods for comparison:

  • Sunflower seeds: 0.39 mg/kg
  • Poppy: 0.51 mg/kg
  • Apples: 0.0017 mg/kg
  • Tomatoes: 0.0046 mg/kg

The maximum tolerable intake of cadmium is 0.00034 mg per kg body weight. A person weighing 60 kg could therefore ingest 0.0204 mg of cadmium per day without having to fear damage to his health. With 10 g of Asian algae you would absorb about 0.0044 mg of cadmium, so algae do not pose an excessive risk with regard to cadmium.

Aluminum in seaweed

The aluminum content in algae was also examined. For Asian algae, it was 11.5 mg/kg and for European algae, it was 12.3 mg/kg. According to the Federal Institute for Risk Assessment, weekly aluminum intake should not exceed 1 to 2 milligrams per kilogram of body weight.

Assuming the European value of 12.3 mg per kg and calculating this down to an algae salad with 10 g of dried algae, this results in an aluminum value of 0.123 mg. Much smaller amounts of seaweed are used for seasoning.

For comparison: If a person weighs 70 kg, according to the above recommendation, they could take in 70 to 140 mg of aluminum per week without having to fear any damage to their health – especially not if you take into account the measures mentioned in our article Eliminate aluminum to prevent aluminum is stored in the body in the first place.

Arsenic in seaweed

Chinese researchers also examined seaweed for arsenic: red seaweed contained an average of 22 mg arsenic per kg – brown seaweed 23 mg per kg. It turned out that 90 percent of the arsenic was organic, which was detected in the algae. Compared to inorganic arsenic, this is not harmful. However, Hijiki is known to accumulate inorganic arsenic. For this reason, as a precautionary measure, hijiki should not be eaten regularly.

A tolerable intake of 15 µg arsenic per kg body weight per week was originally set. However, this value was withdrawn in 2010. A value for the maximum tolerable arsenic intake has not been specified since then – the previous data are not sufficient for this.

However, maximum levels of inorganic arsenic have been defined for products made from rice: Depending on the product, these may contain between 10 and 30 mg of inorganic arsenic per kg. If this value were applied to the above measurements of algae, these would be in the permissible range (assuming 10 percent inorganic arsenic in algae).

Mercury in seaweed

Many foods contain mercury – especially fish, but also meat, vegetables, and mushrooms. Mercury can accumulate in the organs and damage the entire body. Some mercury compounds can also penetrate the blood-brain barrier and cause neurological damage.

However, the National Food Institute in Denmark has determined that seaweed harvested in Denmark has only a low level of mercury and poses no health risk. For sea lettuce, for example, an average value of 0.007 μg per g was found. For comparison: tuna contains around 0.33 μg per g, although larger portions are eaten than algae. Asian algae are also only slightly contaminated with mercury, as Korean researchers have found.

Uranium in seaweed

Uranium is a radioactive element that occurs naturally in rock, soil, and air, but is also found in some phosphate fertilizers and is a waste product from the nuclear industry. It can e.g. B. via fish, vegetables, cereals, and drinking water in the human diet. Uranium is particularly harmful to the kidneys.

In 2018, the Federal Office of Consumer Protection and Food Safety examined the uranium content in dried algae leaves for the first time. The measured values ​​are high but too low to represent a health risk, according to the Federal Office. The countries from which the algae containing uranium came were not specified.

Organic seaweed is less polluted

In summary, the positive properties of algae far outweigh them. Nevertheless, it is advisable to also rely on algae with an organic label, because their pollutant load was significantly lower in analysis than that of conventional algae. Brown algae also tended to be less polluted than red algae.

This is how seaweed is grown

Much of the world’s algae harvest comes from algae grown specifically for human consumption. 80 percent of algae cultivation takes place in China and Indonesia, the remaining 20 percent mainly in South and North Korea and Japan. The algae are grown in huge round tanks or cultivated in the sea on lines and nets. Synthetic fertilizers are prohibited in organic algae cultivation, but algae generally do well without fertilizers anyway.

Only a small part of the global algae harvest still comes from so-called wild collections of naturally growing algae. Big producers are Chile, Norway, and also here China, and Japan. In Europe, the harvest of wild algae is even more important than algae cultivation due to its long tradition. Wild-collected organic algae may only be harvested in clean waters, i.e. away from ports, sewage pipes, nuclear power plants, etc. In addition, manual harvesting is preferred, and only enough to maintain stocks.

Buy seaweed – you should pay attention to this

In Europe, seaweed is usually sold dried. You can buy them in larger supermarkets, Asian shops, and online shops. Fresh algae, on the other hand, are rarely found. You are most likely to get them in the delicatessen departments of larger supermarkets or in online shops – they are often pre-prepared seaweed salads. Furthermore, seaweed is sold in jars or in the form of seaweed leaves, seaweed pasta, seaweed chips, seaweed flakes, and seaweed powder (for seasoning).

As mentioned above, when buying algae, you should opt for organic products. In addition, you should choose products for which the iodine content or a maximum consumption amount in relation to the iodine content is specified. If this information is missing, you can ask the manufacturer. For example, a manufacturer that states the iodine content of its products is Arche. You can find Arche products in particular in organic supermarkets and health food stores.

Since seaweed is also harvested and cultivated in Europe, it makes sense to buy it instead of the well-traveled seaweed from Asia. Large European algae producers include France, Norway, Ireland, and Iceland.

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