Data describing the efficacy of flaxseed products on glycemic outcomes, oxidative and inflammatory markers in patients with T2DM from six meta-analyses of RCTs.
| Reference | Number of studies/patients included | Intervention/dosage forms | T2DM outcomes | Conclusions | Study limitations |
|---|---|---|---|---|---|
| Fornari Laurindo et al. [78] (2025) | 11 RCT (2 for flaxseed oil FO)/n = 203 | Flaxseed oil alone or in combination with other seed oils | Significant decrease in the oxidative stress marker MDA in T2DM patients. Flaxseed oil improved lipid profiles; however, FBG was not changed. | Reduced lipid levels and oxidative stress. However, no effects were observed on FBG levels. | A limited number of clinical trials and subjects were included.Significant heterogeneity in intervention duration, intervention times, and dosage form. Some studies analyzed a combination of flaxseed oil and other seed oils. |
| Musazadeh et al. [79] (2025) | 16 RCTs/n = 1,136 | Flaxseed/Flaxseed oil products | Significantly reduced BW and WC, but not BMI, blood pressure, TC, or TG in T2DM patients. | Flaxseed supplements reduced anthropometric indices and triglyceride levels, but blood pressure or lipids were not impacted. | A limited number of clinical trials and subjects were included.Significant heterogeneity in intervention duration, intervention times, dose, and dosage. |
| Xi et al. [80] (2023) | 13 RCTs/n = 1,720 | Flaxseed/flaxseed oil products | Significant reduction in HbA1c in T2DM patients. BMI, BW, BP, FBG, or HOMA-IR, quick insulin sensitivity check index, or lipid parameters were not changed. Sub-group analyses showed significant reductions in FBG if the baseline FBG was ≥ 8.0 mmol/L or baseline HbA1c ≥ 7.0%. Elevation in HDL-C and reduced TC and LDL-C were also significant. | Flaxseed supplementation significantly reduced HbA1c in participants with T2DM, especially those with poorly controlled blood sugar levels. | Many RCTs with a small number of subjects were included.Significant heterogeneity in the patient characteristics, flax products used, intervention duration, intervention times, and dosage.While the study showed an improvement in HbA1c in patients with T2DM, sensitivity analyses showed the result was not stable. The study included patients with stable blood glucose levels, that may have biased the study. High risk for publication bias was reported. |
| Villarreal-Renteria et al. [81] (2022) | 7 RCTs/n = 355 | Milled or ground flaxseed | FBG, HbA1c, HOMA-IR, and insulin levels were significantly reduced. | Overall improvement in glucose levels and reduced IR in prediabetes and T2DM patients. Effective doses not reported. | A small number of studies and subjects. High risk of bias as blinding in some RCTs was not optimal.Significant heterogeneity due to products used, patient population, and doses. |
| Mohammadi-Sartang et al. [82] (2017) | 25 RCTs/n = 2,592 | Flaxseed/Flaxseed products | Significant reduction in FBG and insulin levels, as well as HOMA-IR index. Supplementation raised the QUIKI. No effect on HbA1c. Sub-group analysis showed that these effects were significant only for whole or ground flaxseed but not flaxseed oils or lignan extracts. | Whole flaxseed supplements may improve glycemic control in patients with high FBG treated for more than 12 weeks. | While 17/25 studies were of high quality, most of the trials had small sample sizes, n < 30–50 participants. Significant heterogeneity among studies, different methodologies, and different populations. |
| Ursoniu et al. [83] (2017) | 17 RCTs/n = 1,256 | Flaxseed powder/extract/oil | No significant effect on CRP levels in T2DM patients. | Flaxseed supplementation does not alter CRP plasma levels. | A small number of clinical trials were analyzed. Some RCTs were of low quality. Significant heterogeneity between RCTs due to the wide range of supplement dosage forms and doses used. |
BMI: body mass index; BP: blood pressure; BW: body weight; CRP: C-reactive protein; FBG: fasting blood glucose; HbA1c: glycated hemoglobin; HDL-C: high-density lipoprotein cholesterol; HOMA-IR: homeostasis model assessment of insulin resistance; LDL-C: low-density lipoprotein cholesterol; MDA: malondialdehyde; RCTs: randomized controlled trials; T2DM: type 2 diabetes mellitus; WC: waist circumference; QUIKI: quantitative insulin sensitivity check index; TC: total cholesterol; TG: triglycerides.
The supplementary material for this article is available at: https://www.explorationpub.com/uploads/Article/file/101474_sup_1.pdf.
SMW: Investigation, Writing—original draft, Writing—review & editing. TOL: Validation, Writing—review & editing. BAA: Investigation, Validation, Writing—original draft, Writing—review & editing. GPA: Investigation, Writing—review & editing. GBM: Conceptualization, Investigation, Writing—original draft, Writing—review & editing. All authors read and approved the submitted version.
The authors declare that they have no conflicts of interest.
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All information and data in this review are in the public domain. The primary data for this systematic review were sourced online from databases listed in the methods. Referenced articles are accessible on Cochrane Library, PubMed Central/Medline, Embase, Google Scholar, and the Scopus electronic databases. Additional supporting data are available from the corresponding author upon request.
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