Sea Vegetables

P15_05Harvesting plants from the sea may be the wave of the future, but many varieties of seavegetables have been enjoyed since before the development of agriculture.

Properly prepared, high-quality sea vegetables are delicious and provide a concentrated source of nutrition.Being an island nation surrounded by sea, Japan harvests many types of sea vegetables from all around the country. The high life expectancy of the Japanese is thought to be down to the nation’s healthy diet that includes sea vegetables as one of the regular items in the daily meals for long.

Japanese sea vegetables are getting attention as a trendy superfood, and they are full of flavor, versatile and low-calorie plants, containing an abundance of minerals, vitamins, and dietary fiber. Mitoku offers a range of dried sea vegetables – each with different flavor, texture and color so they give dishes contrasting flavors and excitements. Wild or cultivated, they are harvested from environmentally protected areas designated as national natural treasures. Each is prepared using old artisan methods. They also add extra nutrition to any soup, salad and vegetable dishes. It can make a healthy snack too.

Most common are nori, kombu, wakame and arame. Kombu kelp is chiefly sold dried and features in many dishes, although its primary use is as an ingredient for umami-rich, dashi stock. Because it has auspicious associations kombu is used widely in celebration foods, and in dried form it is a typical offering of Shinto rituals.

Mitoku has been working with sea vegetable makers from numerous regions since our establishment 50 years ago to supply Japanese sea vegetables to the world.

  • Kanten

    • Kosher
    • Gluten free
    • Wheat free
    • Vegan
    • Dairy free

    Gelidium amansii, ogonori gracilaria verrucosa

  • Nori

    Toasted dried sea vegetabls (Pyropia yezonensis)

  • Wakame

    • Gluten free
    • Wheat free
    • Vegan
    • Dairy free

    Dried sea vegetables (Undaria pinnatifida)

  • Kombu

    • Kosher
    • Gluten free
    • Wheat free
    • Vegan
    • Dairy free

    Dried sea vegetables (Laminaria longissima/Laminaria angusta)

  • Hijiki

    • Vegan

    Dried sea vegetables (Hizikia fusiforme)

  • Arame

    • Vegan

    Dried sea vegetables (Eisenia bicyclis)

Sea Vegetable Quality

Like land vegetables, the quality of sea vegetables can vary. In Japan, most sea vegetables are supplied in bulk by brokers or middlemen who buy from growers or harvesters in large quantities. The bulk sea vegetables are then packaged under various Oriental and natural foods labels. Some sea vegetables are now artificially cultivated and others are picked from or grown in polluted waters. However, the highest quality sea vegetables are picked wild from clean waters at just the right time. Mitoku sea vegetables are bought from the small, traditional suppliers described on the following pages, who have been harvesting wild sea vegetables as a way of life for decades.

From old site

For centuries, Oriental medicine has recognized that sea vegetables contribute to general well-being and especially to the health of the endocrine and nervous systems. Over the last few decades, medical researchers have discovered a diet that includes sea vegetables reduces the risk of some diseases and helps the body eliminate dangerous toxins. In fact, surveys show that people living in areas where sea vegetables are regularly included in the diet tend to live longer, healthier lives.

One reason sea vegetables are so nutritious is due to the ideal growing conditions of the world’s oceans. Living in a marine environment, sea vegetables have ready access to the abundance of nutrients found in the ocean. The gentle wave action of the underwater currents delivers nutrients to sea vegetables and carries away the plants’ waste. As a result, sea vegetables concentrate minerals and other nutrients at levels that are rarely found in land plants.

Although biologists classify sea vegetables as plants, the only important characteristic they share with typical land plants is the ability to make food (sugar) from sunlight, carbon dioxide, and water. Both sea and land plants use a light-activated catalytic chemical reaction to accomplish this. In green sea vegetables, like land plants, the catalyst is the green pigment chlorophyll. In red and brown sea vegetables, other pigments predominate. One way scientists classify sea vegetables is by their color. Most of the popular edible sea vegetables, such as wakame, kombu, arame, and hijiki, are classified as brown sea vegetables (algae) while nori, the most widely used sea vegetable, falls under the classification of red sea vegetables. Scientists believe that the different colored pigments allow sea vegetables to make food in the ocean depths, where light intensity and wave lengths are different from those found at the surface.

Beyond the ability to make food, sea vegetables bear little resemblance to land plants. Since they have no true leaves, stems, or roots, and as they reproduce by a primitive method that does not utilize flowers or seeds, sea vegetables are structurally more like mushrooms and other fungi. From a chef’s point of view, the simple structure of sea vegetables is an asset. Without woody roots and stems, there is much more to eat.


Besides their impressive nutritional profile, sea vegetables offer other health benefits. For centuries, Oriental medicine has recognized that sea vegetables contribute to general well-being and especially to the health of the endocrine and nervous systems. Over the last few decades, medical researchers have discovered a diet that includes sea vegetables reduces the risk of some diseases and helps the body eliminate dangerous toxins. In fact, surveys show that people living in areas where sea vegetables are regularly included in the diet tend to live longer, healthier lives.

For thousands of years, herbalists and pharmacologists around the world have tested and experimented with medicinal plants. Many modern medicines are either derived from plant extracts or are synthetic copies of substances originally derived from plants. Although there is a long tradition of using sea vegetables as medicine in Japan and China, modern medicine usually regards these remedies as mere folklore.

More recent medicinal treatments using sea vegetables, sea water, and mud from the ocean – such as thalassotherapy and algotherapy – are primarily external applications rather than internal medicines. Advocates of these therapies claim reduced or cured symptoms of hypertension, chronic rheumatism, gout, neuralgia, asthma, eczema, and even hemorrhoids.

Current interest in the medicinal value of sea vegetables began in 1927, when Professor S. Kondo, of Tohoku University, discovered that Japanese people living in regions where large amounts of sea vegetables were eaten regularly enjoyed a particularly long lifespan. For example, on Oki Island in the Shimane prefecture, where people eat an abundance of sea vegetables, there is the longest life expectancy in the nation. Before World War II, it was not uncommon to see Oki women who were 70 years old and older diving in the sea for abalone and red algae.

Since Kondo’s field work, scientists have discovered that sea vegetables, in addition to being very nutritious, have antibiotic and anti-tumor properties. Sea vegetables have also been found to reduce blood pressure and serum cholesterol.

Diets high in sea vegetables have been associated with a lower risk for both colon and rectal cancers. During a study undertaken in Saitama Prefecture, Japan, 700 people were closely monitored for their daily food intake. The study showed that the more sea vegetables an individual eats, the less likely he or she was to develop colon and rectal cancer.

Sea vegetables have also been shown to inhibit breast cancer. In Japan laboratory tests showed that adding sea vegetables to the diet had a significant inhibitory effect on mammary tumor development. The onset of tumors was also delayed and the tumors were smaller.

Another Japanese animal study showed that consumption of sea vegetables inhibited the growth of implanted sarcomas by 89 to 95 percent. According to researchers, more than half of the animals studied showed complete regression. The report also showed promising results with leukemia.

A study done in the early 1960’s seems to confirm the traditional belief that sea vegetables have an antibacterial effect in the intestines. Moreover, in the test tube seaweed extract was shown to be an effective antibiotic drug against common food poisoning bacteria. Sea vegetables have even been shown to inhibit the growth of herpes virus in test tubes.

As a result of this research, a few new medicines have been developed from this underwater harvest, such as laminin, which is used to reduce blood pressure. The most important discovery about sea vegetables for modern living, however, is their ability to cleanse the body of toxins. This powerful cleansing action has been linked to a substance called alginic acid.

Alginic acid is a polysaccharide that is abundant in those sea vegetables classified as brown algae, including kombu, hijiki, arame, and wakame. Scientific researchers, including a team led by Dr. Tanaka at McGill University, have demonstrated that alginic acid binds with any heavy metals found in the intestines, renders them indigestible, and causes them to be eliminated. So, any heavy metals, such as barium, cadmium, lead, mercury, zinc, and even radioactive strontium, that may be present in the intestines will not be absorbed by the body when alginic acid is present.

Doctors Seibin and Teruko Arasaki, Japanese scientists who have published several books about sea vegetables, also report this cleansing property of alginic acid in their book Vegetables From the Sea. They conclude, “Heavy metals taken into the human body are rendered insoluble by alginic acid in the intestines and cannot, therefore, be absorbed into body tissues.”

What’s more, Dr. Tanaka’s research has shown that the alginic acid in sea vegetables actually helps bind and draw out any similar toxins that are already stored in our bodies, thus “lowering the body’s burden.”

Brown algae’s natural affinity for binding with toxic non-organic heavy metals may soon be exploited by industry. Research conducted over the last decade has shown that treating heavy metal-bearing industrial effluents with brown algae is an effective and economical way to detoxify industrial waste. The process, called “biomass biosorption,” is particularly effective for lead and cadmium.


Sea vegetables are virtually fat-free; low in calories; and rich in essential minerals, vitamins, protein, and important trace elements that are often lacking in land vegetables due to soil demineralization. “Sea vegetables contain more minerals than any other kind of food,” claim Doctors Seibin and Teruko Arasaki, authors of Vegetables From the Sea. Analysis has shown that a wide range of minerals account for 7-38 percent of their dry weight. All of the elements essential to health – including calcium, sodium, magnesium, potassium, iodine, iron, and zinc – are present in sea vegetables in sufficient amounts. Of the wide variety of minerals present, calcium, iron, and iodine are of particular importance to people eating a dairy-free, grain-based vegetarian, or macrobiotic diet. For example, 1 cup of cooked hijiki contains over half the calcium found in a cup of milk and more iron than in an egg. Although iodine is, by nature, volatile and somewhat difficult to obtain, sea vegetables contain complex natural sugars that stabilize their iodine, making them excellent sources of this essential mineral.

Edible plants from the sea also contain important vitamins including vitamin A (in the form of beta-carotene), B1, B2, B6, niacin, vitamin C, pantothenic acid, and folic acid. Analysis has shown trace amounts of vitamin B12, which rarely occurs in land vegetables.

A study published in the American Journal of Clinical Nutrition suggests that strict vegetarian nursing mothers with low vitamin B12 levels get an acceptable source of this nutrient by consuming sea vegetables that are naturally high in B12. According to research, the relatively high vitamin B12 content of sea vegetables is thought to reflect a high level of vitamin B12-producing microorganisms in these plants.

For those watching their weight, sea vegetables are the perfect food. Their carbohydrates pass through the digestive system as complex fiber, cleansing the intestines while adding no calories to the diet.

NORI: Except for sushi nori, which comes pretoasted, just before using, nori should be lightly toasted by briefly passing the unfolded sheet over a gas flame or electric burner. The nori is ready when the color changes to a more brilliant green and it becomes crisp and fragrant. (Be careful when toasting – nori is delicate and burns easily.)

Nori is most commonly used to wrap around rice balls, which are probably the most common and popular addition to Japanese lunch boxes and picnic baskets. Nori is also used to wrap other foods, such as Nori-Maki. Cut into 2-inch strips, nori is delicious when wrapped around mouthfuls of warm rice dabbed with umeboshi paste. Crumbled or cut into strips, nori can be used to garnish soups, vegetables, and grain or noodle dishes.

Recently nori is being used as a party food in a variation of nori-maki called te-maki. Te-maki literally means “wrapping by hand.” A quarter sheet of toasted nori is topped with a little sushi rice or noodles along with an assortment of foods such as raw tuna, avocado, or raw vegetables. Condiments such as umeboshi or wasabi may be added, then the nori “package” is rolled into a funnel or cone shape. Te-maki adds an exotic flair to parties, especially when served with hot sake.

Another variety of nori, called ao nori, or green nori, is sold in flake form. Ao nori is used as a garnish or as a seasoning in fried rice. This type of nori is the richest in iron and protein.

WAKAME: The artificial cultivation of wakame, a brown algae related to kombu, is a growing industry in Japan. A technical understanding of wakame’s complex life cycle has enabled businessmen to grow young wakame in tanks and then transplant them to the ocean floor once they are mature enough to fend for themselves. The mature plants are then harvested by machine and dried by hot air.

Although rare, some wild wakame, such as Mitoku’s premium San-Riku Sun-Dried Wild Wakame, is still harvested in Japan. The remote fishing villages on the San-Riku coast of northeastern Japan are renowned for superb seafood. The cold Pacific waters are clean and clear, providing the perfect environment for wakame. The wild wakame from San-Riku has a vitality and depth of flavor that is unequaled by cultivated varieties. There is no fishy taste, and the fronds are particularly tender and tasty.

Around San-Riku, the wakame harvest takes place in early spring, from February until the end of March, as the plants reach maximum size, and before their leaves start to harden. The local fishermen go out in small boats and cut the seaweed by hand, using long, razor-sharp sickles to cut the stems. The wakame is brought back to land, briefly washed, then hung up to dry in the sun for several days until it is completely crisp and dry.

KOMBU: Kombu can be used to create delicious clear soups and cooling pressed salads, as well as hearty stews and bean dishes. In most recipes kombu need not be soaked before use. When soaking is called for, merely soak the kombu until it softens and opens up. The nutritious soaking water can be used in the recipe, or reserved and used at a later time in soups or stews.

Kombu’s most common and important use is in the preparation of dashi, Japan’s multipurpose stock for soups, stews, and sauces. Dashi appears simple, but it is integral to Japanese cooking, since it is the first step in many traditional dishes. The flavor and quality of the stock help determine the taste of the finished dish. Kombu is also good when sliced and used in soups, stews, and vegetable and bean dishes. When cooking beans, the addition of kombu is particularly recommended because it helps soften the beans, reduces cooking time, and makes them easier to digest. The Japanese commonly use kombu to enhance the flavor of the brine or mash that is used to marinate various types of pickles. Sometimes, the kombu itself is one of the ingredients to be pickled. Kombu can also be cooked in a seasoned broth, wrapped around pieces of burdock or other vegetables, and then served as hors d’oeuvres.

A nutritious condiment can be made by roasting kombu then grinding it to a powder. First, cut the kombu into small pieces and place in an unoiled skillet over medium heat. Stir the kombu pieces constantly until they become very crisp. Transfer the roasted kombu pieces into a bowl or a suribachi (Japanese grinding bowl), and grind the kombu into a fine powder. Add this powder as a seasoning to soups, or sprinkle it over grains and vegetable dishes before serving.

HIJIKI&ARAME: When properly cooked and presented, hijiki is very attractive. Its shimmering black color adds vivid contrast and beauty to any meal. When planning a meal that includes hijiki, try to use foods with colors that create an attractive contrast to the blackness of the hijiki. Carrots, winter squash, and pumpkin offer deep orange colors, while lightly steamed broccoli and watercress provide bright green tones. Cold hijiki salad topped with a creamy white tofu dressing and a sprinkle of finely minced green onion or parsley presents an attractive contrast of colors, and is particularly appealing on a hot summer day. Although hijiki and arame are prepared in similar ways, there are a few important differences. Hijiki is thicker, somewhat coarser, and has a strong ocean flavor. Arame’s considerably milder aroma and taste make it a good choice for anyone just beginning to use sea vegetables.

Both should be rinsed quickly but carefully to remove foreign matter such as sand and shells, then soaked in water to cover. However, because of the difference in their textures, hijiki should be soaked for ten minutes, while the more delicate arame needs only five. Longer soaking draws out the important nutrients and waterlogs these vegetables making them less able to absorb the flavor of seasonings used in the recipe.

If you use the soaking water in cooking, pour it carefully so as not to disturb any sand or shells that may have sunk to the bottom. Keep back a small amount in the bowl and then discard it. Using the soaking water results in a somewhat stronger flavor and decreases the need for added salt or shoyu. In the recipes that follow, fresh water was used, so if you choose to use soaking water, cut the amount of shoyu in half, and add more only if needed.

Take into consideration that soaking increases the dried volume of arame and hijiki by about three times. One cup of dried hijiki will become three cups when soaked. For general preparation, squeeze out excess water after soaking and sauté the sea vegetable in a little oil for a few minutes. Add soaking water or fresh water to almost cover and simmer until the vegetable is tender and most of the liquid is absorbed (about thirty-five minutes for hijiki and twenty-five minutes for arame). Finally, season the tender vegetables with shoyu and mirin (if desired), and cook a few minutes more. Both hijiki and arame are delicious when sautéed with sweet vegetables such as carrots, slow-cooked onions, winter squash, lotus root, shiitake, and dried daikon radish. Hijiki and arame are also delicious when served with deep-fried fresh tofu or when sautéed with dried tofu. A little chopped hijiki or arame can be combined with cooked rice, millet, or barley. Hijiki and arame are good additions to salads, especially when topped with a tofu dressing.

Although the following recipes are for hijiki, if you wish to use arame, simply make the previously mentioned adjustments in soaking and cooking time.

KANTEN: Naturally made snow-dried kanten is available in bars and flakes in most natural foods stores. The Mizoguchi family’s kanten is sold in the United States under the Emerald Cove, Erewhon, Mitoku Macrobiotic, Sound Sea Vegetables, and Tree of Life labels. A powdered variety is often sold in Oriental foods stores, but this type is usually made by a chemical process that is used in large factories. Read labels carefully and look for the words “snow-dried.”

According to Peter and Montse Bradford, authors of Cooking With Sea Vegetables, the jelling ability of natural kanten varies according to the acidity or alkalinity of the food with which it is used. Acidic foods may require more kanten than alkaline foods do. Testing the recipe is recommended by taking a spoonful of the heated mixture and allowing it to rapidly set on a cool surface. If the mixture does not set in a few minutes, add a little more kanten to the pot and simmer a few more minutes.

To use kanten bars, tear them into several pieces and soak them in water for thirty to sixty minutes. Remove the kanten, squeeze out any excess water, and place in a saucepan along with the liquid called for in the recipe. The liquid should be cold or at room temperature. Bring to a simmer over medium heat without stirring. Once the liquid begins to simmer, stir occasionally until the kanten dissolves (about two to three minutes).

Prepackaged flakes need not be soaked. Simply sprinkle the measured amount over the liquid before heating and proceed as instructed for kanten bars. In any recipe, flakes can be substituted for bars and vice versa. The jelling strength of one bar of kanten is equal to two slightly rounded tablespoons of flakes.