The effect of flaxseed supplementation on anthropometric indices, blood pressure, and lipid profile in diabetic patients: A GRADE-assessed systematic review and meta-analysis of randomized controlled trials

Background and aims: Numerous clinical studies have suggested that flaxseed supplementation may be effective in diabetic patients, but the findings are controversial. Therefore, this study aimed to examine the effects of flaxseed on blood pressure, anthropometry, and lipid profile parameters in diabetic patients. Methods: PubMed, Cochrane Library, Web of Science, Scopus, Embase databases, and Google Scholar were searched until June 2024. A random-effects model was utilized to analyze standardized mean differences (SMDs). Results: Meta-analysis of 16 trials with 1136 participants indicated significant improvements in weight (SMD: 0.81; 95 % CI: 1.54 to -0.09, p = 0.028; I² = 88.7 %, p < 0.001), waist circumference (SMD: 1.54; 95 % CI: 2.77 to -0.31, p = 0.002; I² = 85.3 %, p < 0.001), and triglyceride (SMD: 0.56; 95 % CI: 1.02 to -0.10, p = 0.016; I² = 87.4 %, p < 0.001), but not BMI (SMD: 0.63; 95 % CI: 1.28 to 0.02, p = 0.058; I² = 87.9 %, p = 0.005), systolic blood pressure (SMD: 0.50; 95 % CI: 1.25, 0.25, p = 0.193; I² = 87.6 %, p < 0.001), diastolic blood pressure (SMD: 0.74; 95 % CI: 1.51, 0.03, p = 0.060; I² = 88.1 %, p < 0.001), total cholesterol (SMD: 0.43; 95 % CI: 0.99 to 0.12, p = 0.128; I² = 93.6 %, p < 0.001), low-density lipoprotein cholesterol (SMD: 0.09; 95 % CI: 0.87 to 0.70, p = 0.830; I² = 96.3 %, p < 0.001), and high-density lipoprotein cholesterol (SMD: 0.08; 95 % CI: 0.30 to 0.46, p = 0.673; I² = 87.2 %, p < 0.001). Conclusion: Flaxseed supplementation effectively reduces anthropometric indices and triglyceride levels in individuals with type 2 diabetes but does not suggest any benefit on blood pressure and other lipid profile parameters. Therefore, conducting more extensive, well-designed trials to validate these findings is crucial.