Effect of flaxseed or psyllium vs. placebo on management of constipation, weight, glycemia, and lipids: A randomized trial in constipated patients with type 2 diabetes

Clin Nutr ESPEN. 2019 Feb:29:41-48. doi: 10.1016/j.clnesp.2018.11.002. Epub 2018 Nov 17.


Background: Both flaxseed and psyllium have previously been shown to reduce constipation symptoms, weight, glycemic and lipid levels, and we postulate that treatment with flaxseed and psyllium may have similar benefits.

Objective: To compare constipation symptoms, weight, glycemia, and lipids in constipated patients with type 2 diabetes (T2D) who received baked flaxseed or psyllium versus those who received a placebo.

Methods: In a single-blinded, randomized controlled trial, 77 constipated patients with T2D were randomized into three groups. Patients received either 10 g flaxseed or psyllium pre-mixed in cookies or placebo cookies twice per day for a total of 12 weeks. The constipation symptoms, body mass index (BMI), fasting plasma glucose (FPG), glycosylated hemoglobin (HbA1c), and lipid profile were determined at the beginning and end of 4, 8, and 12-week period. Constipation was assessed with the ROME III criteria score.

Results: The flaxseed appear to be superior to psyllium for improving constipation symptoms, weight, glycemic, and lipid control. The change from baseline of constipation symptoms (P = 0.002), stool consistency (P < 0.001), weight (P < 0.001), BMI (P < 0.001), FPG (P = 0.004), cholesterol (P = 0.010), LDLC (P = 0.031), and cholesterol/HDLC ratio (P = 0.019), was significantly improved in both flaxseed and psyllium groups than in the placebo group. The compliance was good and no adverse effects were observed.

Conclusion: Although both flaxseed and psyllium may decrease constipation symptoms, weight, glycemic and lipid levels, treatment with flaxseed appear to be superior to psyllium.

Trial registration: Registered under Iranian Clinical Trials Identifier no. IRCT20110416006202N2.

Keywords: Constipation; Diabetes; Efficacy; Flaxseed; Glucose; Lipid; Psyllium.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Blood Glucose / drug effects*
  • Body Mass Index
  • Body Weight / drug effects*
  • Cholesterol / blood
  • Constipation / drug therapy*
  • Diabetes Mellitus, Type 2 / complications*
  • Female
  • Flax / chemistry*
  • Humans
  • Iran
  • Lipids / blood*
  • Male
  • Middle Aged
  • Psyllium / pharmacology*


  • Blood Glucose
  • Lipids
  • Psyllium
  • Cholesterol

Associated data

  • IRCT/IRCT20110416006202N2