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Evidence-Based Supplement Research
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Flax and Reduced Diastolic Blood Pressure

Research synthesisLow evidenceSmall effect3 studies · 1 beneficial · 2 neutral · 0 harmful

Across 3 studies, 1 reported a moderate beneficial effect of flaxseed oil on diastolic blood pressure (DBP) in adults with metabolic syndrome, while 2 meta-analyses found no significant effect in broader populations. The beneficial study used 25 mL/day of flaxseed oil for 49 days, but the aggregate evidence is predominantly neutral with small effect sizes. Median study duration was 49 days, though only 1 study reported duration.

  • Effective dose range: 25 mL/day (from the single beneficial study)
  • Studied populations: patients with metabolic syndrome (MetSyn)

Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. Many of the included studies did not reach statistical significance — effect may be smaller than the predominant direction suggests. The beneficial effect was observed in a single RCT with a specific form (flaxseed oil), while the two meta-analyses (which included varied flaxseed forms and populations) showed neutral results, suggesting the benefit may not generalize.

Generated Jun 12, 2026
Doses used in studies
  • mL/day: 25 (median 25, IQR 25–25) — 1 study
Time to effect
Median: 7 weeks · IQR 7 weeks–7 weeks · Range 7 weeks–7 weeks — Reported in 1 of 3 studies
3 of 3 papers
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