Konjac

Studies in people

• Concern

  Gut comfort¹

  In adults, 3,000 mg of konjac glucomannan daily for 12 weeks caused some people to have diarrhoea or constipation.

• Benefit

  Blood fat levels²

  In 13 Japanese men, adding konjac to rice gruel lowered free fatty acids and changed triglycerides.

• Benefit

  Weight loss³

  Konjac fiber may help overweight people lose weight by making them feel full, but scientists need more research.

• Benefit

  Cholesterol and gut health⁴

  In people, taking konjac glucomannan as a supplement lowered cholesterol and improved how the body handles food.

• Benefit

  Blood sugar levels⁵

  In adults, glucomannan supplements lowered fasting blood sugar but did not change blood sugar after meals.

• Concern

  Vitamin absorption from food⁶

  Konjac mannan reduced how much vitamin E people absorbed from a test meal, but not vitamin B12.

• Benefit

  Constipation in athletes⁷

  In athletes with constipation, taking konjac glucomannan for 8 weeks eased gut symptoms and changed gut bacteria.

• No harm found

  Belly pain in children⁸

  In children with belly pain, konjac fiber worked no better than a placebo.

Animal and lab studies only

• Benefit

  Blood sugar in diabetes¹³

  In animal studies, konjac glucomannan lowered blood sugar and blood fats in rats with type 2 diabetes.

• Open question

  Gut bacteria and digestion¹⁴

  In lab studies, konjac fiber was not broken down by digestive enzymes and fed gut bacteria, making less gas than inulin.

• Benefit

  Constipation relief¹⁵

  In animal studies, konjac oligosaccharides helped constipated rats poop more often and with more gas relief than regular konjac fiber.

Study type not stated

• Benefit

  Blood sugar and cholesterol⁹

  Konjac is a fiber that may help lower blood sugar, cholesterol, and blood pressure, and support weight loss.

• Open question

  Blood sugar and weight¹⁰

  Konjac glucomannan is a fiber that may help with weight, blood sugar, and gut health, but can cause stomach upset.

• Benefit

  Blood sugar control¹¹

  Konjac may help control blood sugar, but scientists say more studies in people are needed.

How it’s made and used

• Ketchup texture and thickness¹²

  In lab tests, konjac with xanthan made ketchup more stable, and tasters liked it as much as regular.

The signal at the top counts the findings in people and in animal and lab studies. A concern in studies of people outranks animal and lab studies, and “No concerns” needs at least one finding in people. When most findings in people point one way, the page leans that way (“Mostly”), and every finding is still shown. Findings whose study type is not stated are shown but not counted. This page is a reference, not medical advice. It describes what regulators and published research say. Talk to a doctor or dietitian about your own diet.

Expert panels that weigh all the research. Shown for context: the signal at the top does not count them.

• UN and WHO food additive experts (JECFA), 1996

  No daily limit needed (“ADI not specified”, JECFA’s term for very low toxicity).