Myth-buster
A meta-analysis of 17 trials found flaxseed oil lowered systolic blood pressure by less than half a point — a statistically meaningless shift.
This null result contradicts two earlier studies that suggested flax might help, so the overall picture is now genuinely contested — not settled.
Researchers pooled 17 trials and found that flaxseed oil supplements had no significant effect on systolic blood pressure, diastolic blood pressure, or any of four inflammatory markers measured. The tiny average reduction (less than 0.5 mmHg) was indistinguishable from zero, meaning any perceived benefit in earlier, smaller studies may have been due to chance.
Where this fits in the evidence
Pillser has synthesized 3 studies on Flax for Reduced Systolic Blood Pressure — overall evidence strength: Low.
Across 3 studies, 2 reported beneficial effects of flax on reducing systolic blood pressure, while 1 found a neutral effect. The effect sizes were mixed (small to large), with the largest effect observed in a 49-day trial using 25 mL/day flaxseed oil in patients with metabolic syndrome. The median study duration was 49 days, suggesting effects may be observed after 7 weeks of supplementation.
The study
- Meta-Analysis
- n = 17
- 2025-01
- Current hypertension reviews
This is a plain-language summary of a research finding, not medical advice. Pillser surfaces research signals to help you decide what's worth investigating — always consult a qualified professional before changing what you take.