Konjac noodles are a nearly zero-calorie noodle made from the fiber of the konjac plant, a root vegetable native to Southeast Asia. A four-ounce serving contains roughly 10 calories, zero fat, zero sugar, and 3 grams of fiber, making them one of the lowest-calorie noodle options available. They’re also sold under the name “shirataki noodles,” a Japanese term meaning “white waterfall” that describes their translucent, slightly glossy appearance.
How Konjac Noodles Are Made
The key ingredient is glucomannan, a water-soluble fiber extracted from the konjac plant’s corm (a starchy underground bulb, similar to a potato or taro root). To make noodles, manufacturers wash, slice, and dry the corms, then grind them into a fine flour. This flour is mixed with water and a small amount of calcium hydroxide, a food-grade mineral that acts as a coagulant. The alkaline environment causes the glucomannan to form a firm, heat-stable gel that holds its shape during cooking.
The result is a translucent, rubbery noodle that looks somewhat like gelatin but behaves very differently. Unlike regular gelatin, konjac gel doesn’t melt in your mouth or dissolve easily. It stays intact, giving the noodles their distinctive chewy, springy texture. They’re typically packaged in liquid-filled bags and sold in the refrigerated or shelf-stable Asian foods section of grocery stores.
Nutritional Profile
Konjac noodles are remarkable for what they lack. Per four-ounce (112g) serving, according to USDA data:
- Calories: 10
- Fat: 0g
- Carbohydrates: 3g
- Fiber: 3g
- Sugar: 0g
- Protein: 0g
All 3 grams of carbohydrates come from fiber, which your body doesn’t digest for energy. That’s why the calorie count is so low. For comparison, a half cup of cooked whole-wheat penne has about 4 grams of fiber but also comes with around 90 calories and significant carbohydrates. Konjac noodles essentially let you eat a bowl of noodles while consuming almost nothing in terms of calories or macronutrients.
The trade-off is that they provide virtually no protein, vitamins, or minerals on their own. They’re not a complete food. If you’re using them as a meal base, you’ll need to pair them with protein and vegetables to get actual nutrition.
Why Glucomannan Absorbs So Much Water
Glucomannan is one of the most water-absorbent fibers found in nature. Each sugar ring in its molecular chain can bind directly to water molecules through strong hydrogen bonds, giving the fiber an exceptional ability to swell and form thick, viscous gels. Between 5% and 10% of the chain has chemical groups (acetyl residues) that keep it water-soluble, allowing it to dissolve and expand rather than just sitting inert.
This property is what makes konjac noodles feel filling despite having almost no calories. When glucomannan reaches your stomach, it absorbs water and expands, creating a gel-like mass that slows digestion. Food moves through your digestive tract more slowly, which extends the feeling of fullness after eating.
Effects on Blood Sugar and Cholesterol
The viscous gel that glucomannan forms in your digestive system does more than create fullness. It physically wraps around nutrients and slows their absorption in the small intestine. For blood sugar, this means glucose enters your bloodstream more gradually after a meal rather than in a sharp spike. Research published in the journal Foods describes how the gel forms a protective membrane-like barrier that effectively blunts the post-meal rise in blood glucose and insulin. This makes konjac noodles a practical swap for people managing blood sugar levels, since replacing regular pasta with konjac removes most of the carbohydrate load from the meal entirely.
Glucomannan also appears to modestly improve cholesterol. In clinical data, a daily intake of 3 grams reduced LDL (“bad”) cholesterol by about 10% and non-HDL cholesterol by about 7% over three weeks.
One thing the research does not support, however, is the idea that konjac causes significant weight loss on its own. A clinical trial testing glucomannan supplements in overweight adults found no meaningful difference between the supplement group and the placebo group after eight weeks. Both groups lost less than one pound. The fiber may help you feel full, but it doesn’t appear to independently drive fat loss.
Digestive Side Effects
Because glucomannan is such a potent fiber, it can cause bloating, gas, and diarrhea, especially if you’re not used to eating high-fiber foods. The Cleveland Clinic recommends starting with small amounts to see how your system responds, and drinking plenty of water when you eat konjac. Since the fiber works by absorbing water and expanding, inadequate hydration can make digestive discomfort worse.
The Fishy Smell (and How to Fix It)
If you’ve opened a bag of konjac noodles and been hit with an unpleasant fishy odor, you’re not alone. The smell comes from trimethylamine, a compound produced by the reaction between glucomannan and the calcium hydroxide used during manufacturing. The calcium hydroxide itself is odorless, but the chemical interaction creates this byproduct.
The fix is simple. Drain the liquid from the bag, rinse the noodles thoroughly under running water, then sprinkle about a teaspoon of salt over them and rub it in with your hands. Let them sit for about five minutes, then boil them in fresh water for a few minutes. This process eliminates most or all of the odor. For better texture, many cooks also dry-fry the noodles in a hot pan without oil for a couple of minutes after boiling. This drives out excess moisture and gives them a slightly firmer bite that better mimics traditional noodles.
A Note on Konjac Safety
Konjac noodles themselves have a strong safety record, but konjac in other forms has caused problems. In 2001, the FDA issued a warning after several choking deaths among children and elderly adults who ate small, cup-shaped konjac jelly candies. The issue was specific to the candy’s design: mouth-sized portions, a slippery surface, and a firm gel that doesn’t dissolve like regular gelatin. The FDA now detains imports of konjac candies that match those characteristics.
This concern doesn’t apply to konjac noodles, which are chewed and eaten like any other noodle. The choking hazard was about the shape, size, and packaging of specific candy products, not about the konjac ingredient itself.
How to Use Konjac Noodles
Konjac noodles have a mild, almost neutral flavor, which makes them a blank canvas. They won’t taste like wheat pasta, and expecting them to will lead to disappointment. They work best in dishes with bold, flavorful sauces or broths: stir-fries, ramen-style soups, pad thai, or anything with a strong garlic, soy, or chili base. The noodles absorb surrounding flavors well, so the more seasoning in the dish, the better they taste.
They come in several shapes, including thin angel-hair style, fettuccine-width, and even rice-shaped pieces sometimes marketed as “konjac rice.” Some brands mix in small amounts of tofu or oat fiber to soften the texture and add a bit of body, which brings the calorie count up slightly but can make them feel more like conventional noodles.