Side Effects of Konjac Root

While konjac is healthy, its soluble fiber has water-absorbing qualities, which means it can cause gastrointestinal side effects.
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Konjac, also known as "konnyaku," "moyu" or "elephant foot yam," is a tuberous root vegetable. This vegetable is extremely rich in dietary fiber. While konjac is healthy, its soluble fiber has water-absorbing qualities, which means it can cause gastrointestinal side effects.


Konjac Nutrition Facts

Whole konjac tubers are primarily carbohydrates and contain virtually no fat. According to a March 2016 study in the journal ‌Food Reviews International‌, raw konjac tubers are made up of:

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  • 54.7 to 61.6 percent fiber (of which 52 to 59 percent is glucomannan fiber)
  • 12.3 to 20.1 percent starch
  • 2.7 to 3.8 percent sugar
  • 5 to 7 percent protein


Whole konjac also contains small amounts of a variety of nutrients, including vitamin A, vitamin B1 (thiamin), vitamin B2 (niacin), vitamin B3 (riboflavin), calcium, copper, iron, magnesium, manganese, phosphorus, selenium and zinc. Between 2 and 3 percent of raw konjac is made up of these essential vitamins and minerals.

Once processed, konjac can be used as a starch, flour or gel. Konjac flour, which is primarily glucomannan fiber‌,‌ can be used to make low-carb variations of noodles or rice. However, very little konjac is required to make such products. Most konjac products are mainly water, with small amounts (between 1 and 5 percent) of konjac.


Nutritional Value of Konjac Products

The average konjac product is essentially just fiber and no other nutrients. For example, NuLo Organic Foods has a konjac product called Slim Pasta Spaghetti. Every serving of 100 grams (3.5 ounces) of this product contains 9 calories, 4 grams of fiber and 0.2 grams of protein. There are no other nutrients.

You'll find similar nutrition for most pre-packaged konjac products. Better Than Foods' Organic Konjac Rice has 10 calories, 5 grams of fiber and 0.3 grams of protein in a serving of 128 grams (4.5 ounces). This product's label also says that it contains small amounts — between 1 and 4 percent of the daily value — of calcium and phosphorus, as well.


Konjac also has a variety of other uses. The ‌Food Reviews International‌ study states that konjac's texture and neutral flavor make it useful in food processing, where it is used as a thickening agent, preservative and fat replacement. Small amounts of konjac can be found in a variety of food products — anything from the coating on a candy to a filler in a sausage. You might even find it used as an edible packaging on your food.


Fiber Consumption and Konjac

According to Harvard Health Publishing, women should consume between 21 and 25 grams of fiber per day, while men should consume around 25 to 30 grams of fiber per day. The exact amount you should consume is based on your total calorie intake.


There are two types of fiber you can consume: insoluble fiber and soluble fiber. You should get about 60 percent of your daily fiber intake from insoluble fiber, which supports the digestion and excretion of foods as they pass through your gastrointestinal tract. This type of fiber is not broken down during the digestion process.

The remaining 40 percent of your fiber intake should come from soluble fiber, like glucomannan. Soluble fiber can help regulate your blood sugar and cholesterol, and slow digestion. Unlike insoluble fiber, soluble fiber is broken down when digested.


Soluble fiber is broken down during the digestion process; it can help regulate your blood sugar and cholesterol. Insoluble fiber isn't broken down — this type of fiber supports the digestion of other foods as it moves through your gut.

Given that the primary nutrient you'll find in konjac is glucomannan, the main benefit konjac has is its soluble fiber content. According to the Harvard T.H. Chan School of Public Health, increasing your fiber consumption can help reduce your risk for conditions like heart disease, diverticulitis, diabetes and metabolic syndrome. Fiber may even help prevent your risk for certain types of cancer.


Read more:19 High-Fiber Foods — Some May Surprise You!

Konjac Benefits and Side Effects

Most Americans consume just 15 grams of fiber each day, about half of the total amount they should be consuming. Integrating konjac into your diet can help increase your fiber consumption and improve your health.



Konjac also has some benefits that are associated with its specific type of soluble fiber, glucomannan. According to a May 2016 study in the ‌Journal of Food Hydrocolloids‌, glucomannan can:

  • Support weight loss
  • Stimulate the microbes that live in your colon
  • Stimulate the immune system
  • Regulate blood sugar levels
  • Regulate cholesterol levels
  • Reduce triglycerides
  • Promote feelings of fullness
  • Provide the gut with beneficial prebiotics
  • Help manage diverticulitis
  • Help manage diabetes
  • Help manage irritable bowel disease
  • Ease constipation
  • Attach to pathogens and prevent disease

Konjac can also provide people on low-carb or ketogenic diets with an excellent alternative to carbohydrate-based foods. Because they have zero net carbs, foods made with konjac are ideal, and they're also low-calorie products.

Like with all fiber-rich foods, konjac should be consumed in moderation. If you're trying to increase your dietary fiber intake, you shouldn't do so all at once or you're more likely to experience side effects. Consuming fiber in excess can result in a variety of gut issues, including cramping, diarrhea and even constipation.

Konjac's Oligosaccharides and Gut Issues

Konjac's side effects come from the type of carbohydrates it contains. While these are typically beneficial, they're not suitable for everyone.

As a prebiotic, konjac contains fermentable short-chain carbohydrates (also known as FODMAPs or fermentable oligosaccharides, disaccharides, monosaccharides and polyols). The fermentable carbohydrate content in konjac is usually good for your health, but it can also be difficult for certain people to digest. When you eat konjac, these carbohydrates ferment in your large intestine, where they can cause a range of gastrointestinal side effects.

FODMAP-rich foods might cause gastrointestinal problems, like bloating, gas, cramps and stomachaches. Certain people, like those with irritable bowel syndrome, may need to avoid FODMAP-rich foods. If you've been experiencing unpleasant gut issues after eating konjac, you may need to limit your intake of fermentable carbohydrates or simply consume fewer konjac products.




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