Konjac
Useful mainly for people seeking modest LDL cholesterol reduction or appetite/weight support from a soluble fiber.
Quick decision guide
May help most
People seeking modest LDL cholesterol reduction or appetite/weight support from a soluble fiber
Common dosing range
3 g/day glucomannan in three 1 g doses before meals (up to 15 g/day studied)
When to expect effects
Weeks
Watch out for
Choking and gut obstruction risk if taken with too little water or in tablet form
What is it
Konjac (Amorphophallus konjac), also known as elephant yam or devil's tongue, is a flowering plant native to East Asia whose corm (underground stem) is the source of glucomannan, a viscous dietary fiber. Konjac flour is used in traditional Asian cuisine to make jelly, noodles (shirataki), and tofu-like products.
Is it worth it for you?
Use this as a quick fit check, not a diagnosis.
Worth considering if…
Probably skip if…
Evidence at a glance
| Goal | Effect | Best fit | Time |
|---|---|---|---|
ldl cholesterol reduction Good Evidence | ~10% LDL reduction | Adults with elevated LDL cholesterol | Weeks |
weight management Limited Evidence | Small (a few pounds) | Adults using it alongside a reduced-calorie diet | Weeks |
post-meal blood glucose Limited Evidence | Modest | Adults with elevated blood glucose or insulin resistance | Weeks |
constipation Mixed Evidence | Modest | Adults with functional constipation | Days to weeks |
ldl cholesterol reduction
- Effect
- ~10% LDL reduction
- Best fit
- Adults with elevated LDL cholesterol
- Time
- Weeks
weight management
- Effect
- Small (a few pounds)
- Best fit
- Adults using it alongside a reduced-calorie diet
- Time
- Weeks
post-meal blood glucose
- Effect
- Modest
- Best fit
- Adults with elevated blood glucose or insulin resistance
- Time
- Weeks
constipation
- Effect
- Modest
- Best fit
- Adults with functional constipation
- Time
- Days to weeks
Evidence for 4 uses
AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.
ldl cholesterol reduction
Biomarker supportKonjac glucomannan binds bile acids in the gut, prompting the liver to use cholesterol to make more, which lowers circulating LDL. Meta-analyses of RCTs show meaningful reductions in LDL and total cholesterol. This is a biomarker effect; trials have not shown it reduces cardiovascular events.
Bottom line: Reliably lowers LDL cholesterol as a biomarker; cardiovascular-outcome benefit is unproven.
weight management
Supplement benefitGlucomannan forms a viscous gel that slows gastric emptying and increases fullness, modestly reducing calorie intake. EFSA approved a weight-management claim at 3 g/day, though trial results are mixed and the average weight effect is small.
Bottom line: A modest aid to satiety and weight loss when paired with calorie control.
Evidence is mixed
Some RCTs and the EFSA review support modest weight loss, while other trials and meta-analyses find no significant effect.
post-meal blood glucose
Biomarker supportBy slowing carbohydrate absorption, glucomannan blunts post-meal glucose rises and may modestly lower fasting glucose in some trials. Evidence is smaller and less consistent than for cholesterol, and effects are on glucose markers rather than diabetes outcomes.
Bottom line: May modestly improve glucose markers, but evidence is limited and inconsistent.
constipation
Supplement benefitAs a bulking soluble fiber that is partly fermented in the colon, glucomannan can increase stool frequency and improve bowel regularity. Supporting trials are small and quality is limited.
Bottom line: Can help relieve constipation as a fiber, with modest trial support.
How it works
How to take it
What to track
4 commercial forms
Compare the main delivery options and what they’re best suited for.
Konjac glucomannan supplement (capsule or powder)
Used at 3 grams per day for weight management per EFSA. Take with a full glass of water before meals.
Concentrated glucomannan; requires careful use with water.
Shirataki noodles
Calorie-free noodles made primarily from konjac glucomannan and water. Popular in low-calorie cooking.
Whole-food source; lower glucomannan concentration but easy to incorporate into meals.
Konjac jelly
Asian dessert and snack made from konjac flour. Read product labels for serving and safety guidance.
Food product; some forms have been banned due to choking risk in children.
Konjac flour
Used to make noodles, jellies, and other low-calorie foods.
Culinary ingredient for thickening and gel formation.
Safety
Know the common side effects, key cautions, and who should avoid it.
Common side effects
Serious risks
Choking
Esophageal or intestinal obstruction if taken with inadequate water or as tablets
Who should avoid it
- People with swallowing difficulties or esophageal narrowing
- People with GI motility disorders
- Young children (choking risk)
Pregnancy & breastfeeding
Likely acceptable as a dietary fiber, but discuss supplement use with a clinician.
Interactions
Viscosity reduces absorption; separate by 1 hour after or 4 hours before
May enhance glucose lowering
Additive cholesterol-lowering effect
Food sources
| Food | Amount | %DV |
|---|---|---|
| Shirataki noodles (1 cup) | approx 2-3 grams glucomannan | — |
| Konjac jelly (1 serving) | approx 1-2 grams glucomannan | — |
| Konjac tofu (1 cup) | approx 2 grams glucomannan | — |
Shirataki noodles (1 cup)
- Amount
- approx 2-3 grams glucomannan
- %DV
- —
Konjac jelly (1 serving)
- Amount
- approx 1-2 grams glucomannan
- %DV
- —
Konjac tofu (1 cup)
- Amount
- approx 2 grams glucomannan
- %DV
- —
Choosing a product
What to look for on the label — and what to be skeptical of.
Look for…
Be skeptical of…
Frequently asked questions
What is konjac used for?⌄
Konjac is used as a low-calorie food ingredient (shirataki noodles, konjac jelly) and as a dietary fiber supplement for weight management, cholesterol reduction, and blood glucose control.
Are shirataki noodles healthy?⌄
Shirataki noodles are very low in calories and provide soluble fiber that supports satiety, glucose control, and cholesterol management. They are a useful tool in calorie-controlled diets.
Can konjac help me lose weight?⌄
Konjac glucomannan supplements at 3 grams per day before meals have demonstrated modest weight loss benefits in calorie-restricted diets. Konjac foods like shirataki also support satiety with few calories.
Is konjac safe to eat daily?⌄
Yes, konjac foods are safe for daily consumption. Glucomannan supplements should be taken with care and ample water to avoid choking or obstruction risk.
Does konjac taste like anything?⌄
Konjac itself is essentially flavorless and odorless, taking on the flavor of whatever it is cooked with. This neutrality makes it versatile in cooking.
References by claim
ldl cholesterol reduction
post-meal blood glucose
Yoshida et al., 2020 — PubMed (2020) link
Track Konjac with Pilora
Set up dose reminders, check interactions, and join the community in the Pilora iPhone app.
Coming to App StoreDisclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.