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Glucomannan Side Effects & Safety

Evidence:Strong
·

This content is for informational purposes only and does not constitute medical advice. Statements about dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease. Individual results may vary — consult your healthcare provider before starting any supplement. Full disclaimer

Safety Profile

Overall safety rating: Generally Safe

Potential Side Effects

  • Bloating, gas, and abdominal discomfort (especially when starting)
  • Risk of esophageal or GI obstruction if taken without adequate water — ALWAYS take with a full glass of water
  • Loose stools or diarrhea at higher doses

Drug & Supplement Interactions

  • All oral medications — glucomannan may reduce absorption; take medications 1 hour before or 4 hours after glucomannan
  • Diabetes medications — may enhance blood sugar lowering
  • Choking hazard — never take dry or without water; tablet forms have been banned in some countries

Maximum Dose

Do not exceed: 4 g/day; excessive intake may cause GI obstruction if taken without adequate water

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References

  1. ReviewKeithley J, Swanson B (2005). Glucomannan and obesity: a critical review. Alternative Therapies in Health and Medicine. PubMed
  2. ReviewEFSA Panel on Dietetic Products, Nutrition and Allergies (2010). Scientific Opinion on the substantiation of health claims related to konjac mannan (glucomannan) and reduction of body weight. EFSA Journal. DOI
  3. Meta-analysisHaijun Z, Ke Z, Dawei Z, Haedi AR, et al. (2025). Does glucomannan supplementation exert profitable effects on serum lipid profile in adults? A systematic review and meta-analysis.. Prostaglandins & other lipid mediators. DOI PubMed
  4. Meta-analysisMusazadeh V, Rostami RY, Moridpour AH, Hosseini ZB, et al. (2024). The effect of glucomannan supplementation on lipid profile in adults: a GRADE-assessed systematic review and meta-analysis.. BMC cardiovascular disorders. DOI PubMed
  5. Meta-analysisZhang Z, Zhang Y, Tao X, Wang Y, et al. (2023). Effects of Glucomannan Supplementation on Type II Diabetes Mellitus in Humans: A Meta-Analysis.. Nutrients. DOI PubMed
  6. Meta-analysisHo HVT, Jovanovski E, Zurbau A, Blanco Mejia S, et al. (2017). A systematic review and meta-analysis of randomized controlled trials of the effect of konjac glucomannan, a viscous soluble fiber, on LDL cholesterol and the new lipid targets non-HDL cholesterol and apolipoprotein B.. The American journal of clinical nutrition. DOI PubMed
  7. Meta-analysisOnakpoya I, Posadzki P, Ernst E (2014). The efficacy of glucomannan supplementation in overweight and obesity: a systematic review and meta-analysis of randomized clinical trials.. Journal of the American College of Nutrition. DOI PubMed
Show 5 more references
  1. Meta-analysisSood N, Baker WL, Coleman CI (2008). Effect of glucomannan on plasma lipid and glucose concentrations, body weight, and blood pressure: systematic review and meta-analysis.. The American journal of clinical nutrition. DOI PubMed
  2. Meta-analysisHan Y, Zhang L, Liu XQ, Zhao ZJ, et al. (2017). Effect of glucomannan on functional constipation in children: a systematic review and meta-analysis of randomised controlled trials.. Asia Pacific journal of clinical nutrition. DOI PubMed
  3. Meta-analysisZalewski BM, Chmielewska A, Szajewska H (2015). The effect of glucomannan on body weight in overweight or obese children and adults: a systematic review of randomized controlled trials.. Nutrition (Burbank, Los Angeles County, Calif.). DOI PubMed
  4. RCTZhu Y, Chen X, Song G (2025). Effects of konjac glucomannan on gastrointestinal symptoms and gut microbiota in athletes with functional constipation: a double-blind randomized controlled trial.. European journal of nutrition. DOI PubMed
  5. RCTAsghari P, Afshari A, Sadeghi T, Jafarzadeh Esfehani A, et al. (2025). The effects of a newly developed beverage powder supplement on anthropometric measures, body composition, metabolic syndrome components, and appetite in obese or overweight adults: a protocol for a randomized clinical trial study.. Trials. DOI PubMed