Can flaxseed supplementation alleviate blood pressure in patients with metabolic diseases? Evaluating the strength of evidence using a meta-analysis and GRADE approach

Abstract

Objective: Many clinical trials indicate that flaxseed supplementation may exhibit a significant antihypertensive effect, although the findings are inconsistent. This meta-analysis was conducted to provide a more accurate assessment of the impact of flaxseed supplementation on blood pressure in patients with metabolic diseases.  Methods: We conducted a comprehensive search of international databases, such as Scopus, PubMed, Web of Science, and Cochrane Central, with data collection continuing until July 2024. We employed a random-effects model for calculating weighted mean differences (WMDs) to ensure robust analysis.  Results: Meta-analysis of 18 trials (comprising 22 treatment arms) with 1,209 participants revealed significant reductions in both systolic (WMD: -4.30 mmHg; 95% CI: -6.64 to -1.96, p < 0.001; I² = 95.2%, p < 0.001) and diastolic blood pressure (WMD = -2.50 mmHg; 95% CI: -3.88, -1.12, p < 0.001; I² = 95.0%, p < 0.001) following flaxseed supplementation. More significant effects on SBP and DBP were found in trials with an intervention duration of 10-20 weeks, whole flaxseed, subjects with BMI 25-30 kg/m², and in patients with hypertension.  Conclusion: Flaxseed products have been shown to lower both systolic and diastolic blood pressure levels significantly. Together with traditional medicine, flaxseed may be an effective supplement for hypertension treatment.