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Konjac (Glucomannan) – Properties, Uses, Contraindications and More

February 3, 2023
Properties and benefits of glucomannan in konjac

The first time you hear about konjac? You’ve probably just heard that this is an Asian root vegetable. The number of calories per serving is surprisingly low. However, the benefits of konjac go beyond being a good food for those who want to lose weight. Keep reading below to learn about other uses and benefits, their origin, nutritional properties, side effects, contraindications … and much more.

Konjac (Glucomannan)

What is konjac?

Konjac, also known as Chinese root, konjac sponge, or glucomannan. It is a plant native to Asia known for its starchy corm, the bulbous tuber that grows underground. The round corm of the konjac has a similar appearance to yams or taro and can reach more than 25 cm in diameter. In the Asian continent, it is widely used as a substitute for gelatin to thicken and give texture to food, as a bath sponge, and as a remedy in traditional Chinese medicine.

For the konjac root to become edible, it is first dried and then ground to a fine powder; the end product is a dietary fiber called konjac flour, also known as glucomannan powder. Glucomannan, a very abundant water-soluble polysaccharide compound in konjac, has been considered a type of dietary fiber. When it comes into contact with water, it has been observed that it can turn into a kind of natural gelatin and increase its volume 100 times.

In the western world, konjac has been gaining popularity as a dietary supplement (promoting weight loss and controlling cholesterol levels) and as a substitute for gelatin in vegan diets.

Konjac Glucomannan

Nutritional value of konjac

This root is highly nutritious and low in calories; it only contains about 3 calories per 100 grams. Among the main nutritional properties of the raw tuber are:

  • More than 45% glucomannan (fiber). This polysaccharide is believed to be responsible for many of konjac’s beneficial properties. Glucomannan gel has been traditionally used in traditional Chinese medicine to promote detoxification, tumor suppression, blood stasis relief, and phlegm dissolution.1.
  • 9.7% protein. It contains 16 different types of amino acids, including 7 essential amino acids.
  • It is rich in calcium, phosphorus, iron, zinc, manganese, chromium, and copper.

100 grams of konjac flour contain:

  • 37 mg glucomannan
  • 64 g of protein
  • 004 g fat
  • 57 mg of phosphorus
  • 06 mg iron
  • 123 mg of zinc
  • 2 mg manganese
  • 25 chrome
  • 08 mg copper

The fiber in glucomannan is believed to be the safest form of soluble dietary fiber provided by nature .2 Glucomannan cannot be hydrolyzed by the enzymes of the digestive organs. Therefore, its consumption does not lead to the production of new calories. Instead, it helps carry out fundamental processes in the body and prevents the development of many diseases.

Its low caloric intake, satiating effect, and ability to boost nutrient absorption and good intestinal function make konjac have great nutritional value to promote weight loss.

Properties and benefits of glucomannan in konjac

Properties and benefits of glucomannan in konjac

The high fiber content in konjac provides excellent benefits for our health. From lowering blood glucose and cholesterol levels to regulating bowel movements and preventing hemorrhoids or diverticular disease, its benefits continue to be studied worldwide. Some scientists believe that there are still many properties to be discovered in this Asian tuber.

Research so far indicates that glucomannan:

Helps prevent constipation

During a 2008 study, researchers found that glucomannan can help prevent constipation. The study found that adding glucomannan to a low-fiber diet increased the number of probiotic bacteria in the stool and increased bowel movement function by 30%3.

It helps to lose weight.

Consuming fiber regularly helps us keep our appetite in check for longer, making it less likely to overeat or eat between meals. In addition, konjac has the property of “expanding” in the stomach, which causes a feeling of fullness that is very beneficial for those who want to reduce the number of calories per day. According to a 2005 study, adding a glucomannan fiber supplement to a 1,200-calorie balanced diet caused greater weight loss than the same 1,200-calorie diet with a placebo4.

Help reduce cholesterol, blood glucose, and triglyceride levels.

A systematic review from 2008 found that glucomannan can help lower total cholesterol, LDL (bad) cholesterol, and triglycerides 5 . Consuming konjac products also helped reduce body weight and fasting blood sugar levels. The researchers concluded that glucomannan could be an adjunctive therapy for people with diabetes, obesity, and high cholesterol and even reduce cardiovascular disease risk.

Promotes good skin health

According to a 2013 study, konjac root can reduce acne and improve skin health 6. This plant is believed to help reduce the allergic response in the body, thus improving wound healing.

Although more evidence is needed, the glucomannan in konjac may also be beneficial for:

  • Treat dumping syndrome. Dumping syndrome occurs when food moves too quickly from the stomach into the intestines. This can cause the body to release a large amount of insulin, leading to deficient blood sugar levels. Some preliminary research shows that taking glucomannan by mouth may help prevent blood sugar levels from dropping too low after eating in people at risk for this condition. However, there is still some scientific debate about this effect.7.
  • Control hypertension. Initial research shows that glucomannan may improve blood pressure control in people with high blood pressure8.
  • Treat an overactive thyroid (hyperthyroidism). Some researchers have reported that glucomannan, along with methimazole and propranolol, can reduce thyroid hormone levels in people with hyperthyroidism9.
  • Reduce acidity in the body. Being an alkaline food, the consumption of konjac is particularly beneficial in achieving acid-base balance in people who suffer from hyperacidity.

Other studies also link the consumption of konjac with the prevention of cancer (inhibits the metabolism of cancer cells), strengthening the immune system (konjac flour has immunoregulatory activity), and the prevention of foodborne bacterial infections (formation of an antibacterial film on the surface of konjac flour-based foods).

How to use konjac root

Konjac is generally used in supplements and culinary preparations, which can be made from the tuber itself or its flour.


The capsules of konjac powder can be found online or in health food stores. It is imperative to bear in mind that many times these supplements do not have the certification of regulatory institutions (for example, the Food and Drug Administration in the United States (FDA)), hence it is recommended to purchase them only from recognized manufacturers, much better if it comes from an organic source.

Konjac supplements should be taken with plenty of water, preferably before a meal. There is no approved and standardized dosage, so the recommended dosage will vary depending on the manufacturer and the purpose for which it is being used. It usually goes from 2 to 6 grams a day.

Adults (oral route)

  • Constipation: between 2 and 4.5 grams a day, taken in divided doses.
  • High cholesterol: 2.4 to 3.9 grams of glucomannan per day.
  • Type 2 diabetes: daily doses of about 3-4 grams of glucomannan for up to 8 weeks.

Children (orally)

  • Constipation: 100 mg/kg of glucomannan, 1 or 2 times a day for up to 12 weeks.
  • High cholesterol: 1 gram dose of glucomannan 2 times a day for 8 weeks in children 6 years and younger; 1.5 gram dose 2 times a day for 8 weeks in children older than 6 years.

Videos of konjac

One of the most popular konjac food products is noodles, also known as Shirataki noodles. The Japanese word “Shirataki” translates to “white waterfall,” which is indicative of the translucent appearance of these noodles. They are created from the konjac root, have a gelatinous texture, and are widely used to substitute pasta and other carbohydrates, such as rice and potatoes.

Konjac noodles are made up of 97% water and 3% indigestible fiber. Therefore they do not provide calories. They are a type of wet food pre-packaged in liquid. Although the pure glucomannan fiber has no flavor, raw Konjac root flour has a certain fishy odor, which is why Shirataki noodles give off the aroma.

They are straightforward to incorporate, especially in pasta dishes, soups, and salads. A good example is the low-calorie, high-fiber recipe that we suggest below:

Shirataki pasta with spinach and chicken cubes


  • 1 package of shirataki noodles (spaghetti shaped)
  • 1 large onion, finely chopped
  • 2 cups (6 oz) raw spinach, chopped
  • 80 grams of roasted chicken breast, diced
  • 1 teaspoon of olive oil
  • garlic cloves, finely chopped
  • Parmesan
  • Salt and pepper to taste


  • Rinse the konjac noodles thoroughly until they are odorless (follow package directions).
  • In a medium-sized skillet, heat the olive oil over medium heat. Once hot, add the garlic and ¾ parts of the onion; sauté until fragrant, about 3 minutes.
  • Add the spinach and sauté for another 3 minutes until just soft.
  • Now place this sautéed garlic, onion, and spinach mixture in a food processor, add salt/pepper to taste, and process until you get a creamy and smooth mixture.
  • Meanwhile, in the same skillet, sauté the roast chicken pieces and the rest of the onions over medium heat, just for 5 minutes. Add the noodles and spinach sauce.
  • Cook for 3-5 minutes, stirring well to mix all the ingredients and infuse the noodles with the new flavors. If necessary, correct the salt and pepper to taste.
  • Remove from heat, serve on a plate and sprinkle with Parmesan cheese before eating.

Esponja Konjac

The konjac sponge is a facial and body cleansing sponge that is made from the vegetable fibers of the Konjac (dried and ground roots). The process is quite simple; Konjac powder is mixed with calcium hydroxide, heated, frozen, and dried. Calcium produces an alkaline end product that helps balance the skin’s excessively acidic pH. Sometimes powdered charcoal, green clay, or red clay are added to benefit different skin types and better extract impurities from the skin.

Due to its soft texture, this sponge has been used in Japan as a newborn baby bath sponge for more than 100 years. However, it has gained popularity worldwide in recent years as a deep facial cleansing, exfoliating and nourishing item. Its natural vitamin, amino acid, and mineral content help keep skin more nourished and youthful. It has also been shown to inhibit the growth of acne-causing bacteria.

Another aspect that lovers of this sponge highlight are that konjac is a completely natural, non-toxic, biodegradable material, unlike other exfoliants that damage the environment.

How to use the Konjac sponge?

When you see a konjac sponge for the first time, you will notice that it is small and quite hard, but it is better not to get carried away by that first impression.

  1. If this is the first time, soak the sponge in warm water for 15 minutes; You will immediately see how it begins to expand in size and becomes soft. Once you’ve used it several times, you only need to soak it for 1 to 2 minutes to soften and expand fully. Never run the dry sponge over your skin.
  2. Gently squeeze out excess water, pressing the konjac sponge between your palms; do not push hard. If you want, you can apply a small amount of cleaner to it or use it naturally.
  3. Rub it gently into the skin of the face, making an upward circular motion. Focus on dry or pimple-prone areas. This sponge may look like a very mild scrub and give the impression that it needs to be scrubbed hard to work, but it doesn’t. After passing it several times, you will have removed all the dirt, sunscreen, and even makeup. Some people use a little coconut oil to remove heavy makeup.
  4. Finally, rinse your skin well with cold water and apply a moisturizer as you do in your usual beauty routine.
  5. Rinse the konjac sponge under cold water and gently squeeze to remove excess water. It should not be twisted or pulled. Hang it to dry, or put it on a shelf where there is good airflow. Make sure to store it away from light and moisture; avoid leaving it next to the shower.

To disinfect it, it is recommended to soak it in very hot (but not boiling) water for approximately 5 minutes every 2 weeks. After 4-6 weeks, when it no longer expands properly or begins to disintegrate, discarding the sponge and getting a new one is best.

Konjac side effects

Glucomannan, the most abundant compound in konjac, is generally well tolerated; however, like most high-fiber products, it can cause digestive problems in some people, for example:

  • swelling
  • diarrhea or loose stools
  • abdominal pain
  • excess gases
  • nausea

Contraindications, risks, and precautions

According to the FDA, there have been death cases by suffocation in the elderly and children after consuming konjac candies10 . These candies have a gelatinous structure that does not dissolve in the mouth. Hence they can get stuck and cause suffocation. Due to the relatively high incidence of intestinal obstruction and the risk of suffocation, several countries have banned the use of konjac.

It has been reported that konjac supplements can also spread in the esophagus or intestine and cause intestinal obstruction, especially when not taken correctly. The risk is higher if the person:

  • Consume konjac, in any form, without drinking water
  • He is old
  • You have difficulty swallowing

As a general rule, children and pregnant or lactating women should not take konjac supplements. It is recommended to stop taking them, as well as seek medical attention if you have symptoms of an allergic reaction, such as:

  • Difficulty breathing
  • Hives, itching, or skin rash
  • Fast heart rate
  • Swelling

The high fiber glucomannan content in konjac has been shown to lower blood sugar levels. Hence people with diabetes need to control their blood sugar levels very well while consuming it. Consult your doctor before taking konjac if you use insulin or other diabetes medications.

Quick answers to frequently asked questions

How to prepare Konjac pasta?

Making a konjac pasta dish is extremely easy. You have to get any of the konjac options in the market (noodles, angel hair, fettuccine, spaghetti). Assuming you have noodles (a more widespread variant), perform the following steps:

  1. Place the desired amount of Konjac noodles in a colander and rinse for 1 minute with cold water. Drain well.
  2. Bring the noodles to a simmer for 2 to 3 minutes. Nevermore than 3 minutes!
  3. Drain them, place them in a pan and let them dry for 1 minute (without adding oil).
  4. After 1 minute, you should start to hear a squeaking noise. This means that the noodles are ready.
  5. Now add the pasta sauce of your choice and a handful of sauteed or steamed vegetables. Ready! You have prepared a quick, nutritious, and low-calorie pasta dish.

How is konjac flour made?

The Konjac plant can live up to 5 years. However, the root fully matures during the third year of growth and produces its maximum glucomannan fiber. At this time, the tuber is removed from the ground, cleaned, and then peeled. The peeled root is cut into slices and then left to dry under hot air. The dried chips are ground until konjac powder is obtained.

Next, it is necessary to separate the light starch of the konjac from the heavy fiber of glucomannan. For this, the air is blown over the dry powder so that the two carbohydrates are isolated. The glucomannan fiber must then be purified with alcohol to remove any remaining starch, alkaloids, or other additional materials; the result is a pure konjac glucomannan fiber. This highly purified konjac flour is tasteless and can absorb up to 200 times its weight in water.

What is the konjac plant like?

  • The konjac plant belongs to the genus Amorphophallus, and its scientific name is Amorphophallus Konjac.
  • While it is considered a perennial, it can actually live up to 5 years.
  • Its main component is glucomannan fiber, whose production reaches its maximum level after 3 years of growth. Konjac is the only plant that can produce massive amounts of glucomannan fiber.
  • Reaching a diameter of around 8 inches (20 cm), this plant grows in steep mountainous regions at altitudes between 800 and 1,500 meters (2,400 to 4,500 feet).
  • It prefers warm climates in tropical and subtropical zones of the Eastern Hemisphere; under these conditions, a typical harvest yields around 1000 kg per hectare after 3-5 years of growth.
  • Its tuber is very similar to that of yam and taro but with a more oval shape. The largest production area is in the mountains of southwest China, the same native region of pandas.


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My name is Louise Hammond, and I am the creator of this website, a place to find information about tubers, bulbs and medicinal roots. In I show the properties, benefits, characteristics, photos and images, ways of growing and how to make delicious meals from starchy vegetables.