Fiber

What is fiber used for?

Updated 4 Nov 2026

Short answer

The clearest results are for high cholesterol and constipation, in reviews of many trials. For bloating and gas, the results point both ways, and more fiber often adds gas.[1][2][3] What reviews found:

  • LDL cholesterol. In 181 trials with 14,505 people, soluble fiber supplements lowered it by 8.28 mg/dL.[1]
  • Constipation. In 16 trials, 66% of people responded to fiber and 41% to the control treatment. Gas was more common with fiber.[2]
  • Irritable bowel syndrome. In 14 trials, soluble fiber improved overall symptoms and bran did not.[4]
  • Bloating. In a trial of 412 adults, a high-fiber diet raised the risk of bloating by 41%.[3]
  • Blood sugar. In 29 trials in type 2 diabetes, soluble fiber lowered HbA1c, a blood test of average blood sugar, by 0.63%.[5]
  • Blood pressure. In 83 trials, soluble fiber lowered systolic pressure by 1.36 mmHg.[6]
  • Weight. In 62 trials, viscous (gel-forming) fiber lowered weight by 0.33 kg.[7]
  • Gut bacteria. In 64 studies in healthy adults, fiber raised the amount of Bifidobacterium and Lactobacillus in stool, above all with prebiotic fibers such as fructans. The diversity of bacteria did not change.[8]

People who eat the most fiber have 15% to 30% lower rates of death, heart disease, stroke, type 2 diabetes and colorectal cancer than people who eat the least. These numbers come from observational studies of food, and supplement trials were excluded, so they do not show what a powder does.[9]

Sources (9)

  1. Soluble Fiber Supplementation and Serum Lipid Profile: A Systematic Review and Dose-Response Meta-Analysis of Randomized Controlled Trials. Ghavami A, Ziaei R, Talebi S, Barghchi H, Nattagh-Eshtivani E, Moradi S, et al. Adv Nutr, 2023. PMID 36796439
  2. The Effect of Fiber Supplementation on Chronic Constipation in Adults: An Updated Systematic Review and Meta-Analysis of Randomized Controlled Trials. van der Schoot A, Drysdale C, Whelan K, Dimidi E Am J Clin Nutr, 2022. PMID 35816465
  3. Effects of the DASH Diet and Sodium Intake on Bloating: Results From the DASH-Sodium Trial. Peng AW, Juraschek SP, Appel LJ, Miller ER 3rd, Mueller NT Am J Gastroenterol, 2019. PMID 31206400
  4. The effect of fiber supplementation on irritable bowel syndrome: a systematic review and meta-analysis. Moayyedi P, Quigley EM, Lacy BE, Lembo AJ, Saito YA, Schiller LR, et al. Am J Gastroenterol, 2014. PMID 25070054
  5. Effects of soluble fiber supplementation on glycemic control in adults with type 2 diabetes mellitus: A systematic review and meta-analysis of randomized controlled trials. Xie Y, Gou L, Peng M, Zheng J, Chen L Clin Nutr, 2021. PMID 33162192
  6. Effect of soluble fiber on blood pressure in adults: a systematic review and dose-response meta-analysis of randomized controlled trials. Ghavami A, Banpouri S, Ziaei R, Talebi S, Vajdi M, Nattagh-Eshtivani E, et al. Nutr J, 2023. PMID 37833676
  7. Can dietary viscous fiber affect body weight independently of an energy-restrictive diet? A systematic review and meta-analysis of randomized controlled trials. Jovanovski E, Mazhar N, Komishon A, Khayyat R, Li D, Blanco Mejia S, et al. Am J Clin Nutr, 2020. PMID 31897475
  8. Dietary fiber intervention on gut microbiota composition in healthy adults: a systematic review and meta-analysis. So D, Whelan K, Rossi M, Morrison M, Holtmann G, Kelly JT, et al. Am J Clin Nutr, 2018. PMID 29757343
  9. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. Reynolds A, Mann J, Cummings J, Winter N, Mete E, Te Morenga L Lancet, 2019. PMID 30638909

More about fiber

What is fiber?How does fiber lower cholesterol?How much fiber do you need per day?How long does fiber take to lower cholesterol?Is fiber safe?Is fiber from food better than a fiber supplement?

For education; not medical advice. Talk to a doctor before you start, stop or change a supplement.