Kombu - A Sea Vegetable Packed With Savory Goodness

When a person hears the word seaweed, the first thing that is most likely to pop into his mind is a roll of sushi, which is understandable since a lot of variations of this Japanese dish make use of nori, an edible seaweed, as a wrap. In fact, a lot of other soups, snacks, and meals from the Japanese cuisine also rely on seaweed for enhanced flavors.

 However, it is wrong to believe that the seaweeds used by the Japanese for their food are all nori. Since nori is often sold in thin, dried sheets, the ingredient is limited in terms of use.

A more popular type of seaweed that the local community of Japan has found to be more useful is kombu, an edible kelp.

Brief History of Kombu (Horsetail Kelp)

 The edible kelp known as kombu is actually commonly used by other countries in Asia, aside from Japan. Koreans know it to be dashima while Chinese refer to it as haidai. Scientifically speaking, it comes from the seaweed family of Laminariaceae and falls under the subspecies Laminaria japonica or Saccharina japonica. Cultivation of the kelp is primarily done in the seas of Korea and Japan, with the latter producing well over 50% of the total annual production.

 Given the fast decomposition process of the kelp, researchers have found it difficult to pinpoint exactly when the Japanese started regarding it as food. However, traces of wakame, another sea vegetable from the same family as kombu, have been found in Japan’s ruins from the Jomon Period, implying that the act of eating seaweed dates back to as early as 12,000 BC.

 In the late 700s, people in the Tohoku region annually offered their locally produced kombu as a tribute to the Yamato court. When a drying technique was developed during the Muromachi Period, the community applied it to the edible kelp which gave it a longer shelf life. Soon after, kombu became one of the most important exports from the region.

 Kombu quickly found its way to other parts of Japan during the Edo Period, when shipment routes were implemented upon the colonization of Hokkaido. Back then, the Japanese were not fully knowledgeable in the life cycle of kombu which resulted in varied production rates. As such, kombu was sold at relatively high prices.

 It was only in the 20th century that Japan was able to discover and develop efficient methods to cultivate the kelp at sea using ropes. These advanced technologies have greatly helped kombu become readily available at cheaper costs.

 Spring (March/April - May) is considered as the peak harvest season of kombu but the kelp also grows at a steady rate throughout the year, be it winter (December – February) or summer (June-August).

Kombu Kelp vs Nori Seaweed

Kombu and nori are both packed with numerous minerals that many believe to be among the reasons why the Japanese have healthier and longer lives. Although these two come from the sea, they are two separate things.

Kombu is an edible kelp considered as a delicacy in Japan. It is typically sold in thick, dried strips that are almost black in color and feature white, powder-like substances, here and there. These strips are not washed before cooking to avoid losing their savory flavor. Instead, they are either soaked or simmered in water, vinegar, soy sauce, and other seasonings to create flavorful broths and dishes.

Nori, on the other hand, is an edible seaweed that is placed on wooden frames then dried under the sun before being processed to create thin, crispy paper-like sheets. The physical properties of nori make it an ideal wrap for sushi or rice balls. It can also be used as toppings when shredded into strips or flakes.

Basically, kombu serves as a great source of the savory flavor known as umami, while nori serves as a complementary ingredient that provides a subtle taste of the sea.

Nutrition Facts and Benefits of Eating Kombu

As previously mentioned, kombu is a wonderful source of numerous vitamins and minerals that are beneficial to one’s health. In fact, just 3-5 grams of kombu, which amounts to about 5 calories, already contains the following:

     1 g of fiber

     20 mg of calcium (2% of daily value needed)

     1.8 g protein

     750 micrograms of iodine (500% of daily value needed)

     12.2 mg of vitamin C (16% of daily value needed)

     0.3 mg of manganese (16% of daily value needed)

     0.1 mg of vitamin B2 (11% of daily value needed)

     81 micrograms of vitamin A (9% of daily value needed)

     0.1 mg of copper (9% of daily value needed)

     111 mg of potassium (3% of daily value needed)

     0.6 mg of iron (3% of daily value needed)

     0.1 mg of vitamin B6 (3% of daily value needed)

     0.5 mg of vitamin B3 (3% of daily value needed)

     18 mg of phosphorus (3% of daily value needed)

These nutritional facts show that consuming even a small amount of kombu already provides a person of a significant amount of the minerals and vitamins he needs on a daily basis. Furthermore, these nutrients serve as catalysts for the following health benefits:

1.    Aids in Iron Deficiency

Iron deficiency can cause a person to suffer anemia, which can cause fatigue and labored breathing. Everybody needs an adequate amount of iron to be able to function well. Iron is responsible for hemoglobin production, which is necessary for oxygen to be carried in the bloodstream. This promotes healthy skin, nails, and hair, among many other things.

People who have undergone a major surgery, are pregnant, are menstruating, or practice a vegan lifestyle have a higher risk of iron deficiency. As such, they are advised to consume kombu and other iron-rich sea vegetables to be able to consume the recommended daily intake of the nutrient.

2.    Improves Digestion

The amino acids found in kombu help improve digestion by breaking down the heavy starches of consumed food. In addition, the kelp’s glutamic acid, which is responsible for giving kombu a savory taste, also aids in the digestion process by serving as an additional source of fiber.

The improved digestion caused by kombu is also accompanied by a reduced production of intestinal gas. One of the main causes of gas production in the intestines is the lack of certain enzymes that are needed to break down sugars. Bacteria in the intestines react with these sugars to release carbon dioxide and hydrogen gasses, which cause bloated stomachs, as well. The digestive enzymes carried by kombu help alleviate this issue.

3.    Improves Thyroid Function

Among all the sea vegetables, kombu has been proven to contain the highest amount of iodine. Healthy hormone production and thyroid function greatly rely on iodine. Including kombu in one’s diet not only helps in battling hypothyroidism but also provides plenty of antioxidants believed to prevent thyroid-associated heart diseases.

Since the human body cannot naturally produce iodine, several groups such as the American Thyroid Organization often remind the public that everybody is at risk of iodine deficiency.

4.    Prevents Cancer

Sea vegetables are known to carry a lot of anti-inflammatory components. This fact has led scientists to believe that they are great cancer-fighting foods, given their ability to decrease the chronic oxidative stresses and inflammation factors that cause cancer.

Furthermore, since consuming kombu keeps cholesterol level at bay, it also has the potential to decrease the risk of getting breast cancer in women. One of the main causes for breast cancer to develop is high estrogen levels. Given that estrogen production depends on cholesterol level, eating kombu allows women to keep their estrogen level in check, as well.

A study conducted in China also shows that kombu can be used to treat liver cancer. After injecting mice with seaweed extract, initial tumors disappeared or at least reduced in size. As such, kombu is believed to provide antitumor effects.

5.    Prevents Rheumatoid Arthritis

Another Chinese study tackled the effects of kombu on rheumatoid arthritis. By closely observing inflamed cells that cause arthritis, researchers were able to see that the fucoidan content of the sea vegetable was able to reduce the ability of these cells to survive. As such, it is believed that early signs of rheumatoid arthritis can be treated through the consumption of kombu and other algae that contain the sulfated polysaccharide.

Kombu Dashi – A Japanese Broth

 One of the most popular uses of kombu is in making dashi, a common cooking stock used in many Japanese dishes. Dashi comes in several variations namely, kombu dashi (kombu-based), awase dashi (katsuobushi and kombu-based), iriko dashi (sardine-based), and shiitake dashi (mushroom-based). All these types feature a strong, savory flavor that is vital in making authentic Japanese food.

 Kombu dashi separates itself from the other kinds of dashi by serving as a vegetarian stock. It is also fairly easy to make as dictated by the recipe below:


     20 grams of kombu

     4 cups of water


1.    Using a damp cloth, gently clean the kombu without removing the white powdery substances on it.

2.    Pour in four cups of water into a medium-sized pot.

3.    Add in the kombu and allow to soak for a few hours.

4.    Place the pot over medium heat and leave for a 25-minute long simmer.

5.    Remove the kombu before the broth begins to boil to prevent it from tasting bitter and becoming slimy.

6.    Strain the broth using a linen cloth and a sieve.

7.    Store in the refrigerator (3-7 days) or in the freezer (3 weeks), if desired.

The method used above is known as nidashi, which primarily requires the kombu to be simmered. An alternative process for making kombu dashi is mizudashi, which simply involves the kombu being soaked in water overnight, while in the refrigerator.

 Kombu dashi serves as an important ingredient for numerous Japanese dishes such as sushi, miso soup, udon, soba, onigiri (rice ball), and nimono (simmered dish). Without the invention of kombu dashi, the Japanese cuisine would have probably turned out to be something entirely different.

Kombu Tea – Tea Made from Kombu Powder

 Kombu tea, or kombucha, is a brewed beverage made using kombu powder. There is a sweetened, fermented tea from Manchuria that goes by the same name but does not share any similarities.

 Drinking tea is a common practice in Japan, so much so that it is considered to be a part of the country’s culture. There are countless kinds of tea available in Japan such as green tea and black tea. Unlike other teas, kombu tea has a light salty taste that has been enjoyed by the local community since the Edo Period.

 The unique taste of kombu tea has also led many Japanese people to treat it as more than just an average drink. Some people choose to use it as a liquid seasoning similar to how they would use kombu dashi.

Kombu Substitutes – Wakame and Dulse

Although kombu is now a common ingredient that is carried by most grocery stores and supermarkets, it is possible for people to have a hard time searching for the item. This is especially true for foreigners who do not have access to a variety of Japanese goods. There are, of course, online shops that sell kombu and can ship internationally but going for this option will most likely take a while.

 Fortunately, there are other sea vegetables that provide the same flavors as that of kombu and can be used as substitutes:


Wakame, or better-known as sea mustard in English, is an edible seaweed that is also cultivated in Japan, among other countries. It is often used in salad and soup dishes, given its subtle hints of sweetness. This ingredient is widely distributed across the globe in dried form. Similar to kombu, this seaweed softens when immersed in water.

 Just like other sea vegetables, wakame is also packed full of nutrients such as vitamin C, carotenes, and iron. It also has high contents of protein and calcium. Regularly consuming the seaweed promotes healthy skin and hair.


Dulse is a red sea plant that abundantly grows on the coasts of the Pacific Oceans and the Atlantic. It is commonly used in the culinary world of the United States, Ireland, Atlantic Canada, and Iceland as a flavor enhancer, given its rich savory taste.

 The plant has been proven to carry at significantly higher amounts of iron and iodine than wheat. Furthermore, studies have shown that regularly consuming it leaves tonic and purifying effects on the human body.