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Flax

What does the research say about Flax?

3 health outcomes synthesised

Flax (as flaxseed or flaxseed oil) has been studied across 3 health outcomes: diastolic blood pressure, systolic blood pressure, and waist circumference. The strongest evidence, based on 3 studies per outcome, points toward small but potentially beneficial effects on systolic blood pressure, particularly in patients with metabolic syndrome. A common dose used in the single beneficial trial is 25 mL/day of flaxseed oil, though most evidence is considered low or very low strength.

Strongest evidence: No outcomes reached high or moderate evidence strength. The most suggestive findings are for reduced systolic blood pressure, where 2 of 3 studies reported beneficial effects (low evidence strength), with the largest benefit seen in a 49-day trial using 25 mL/day flaxseed oil in adults with metabolic syndrome.

Mixed or weaker evidence: For diastolic blood pressure, 1 of 3 studies (low evidence) showed a small benefit with flaxseed oil, but 2 meta-analyses found neutral results in broader populations. For waist circumference, 1 of 3 studies (very low evidence) reported a small reduction, while 2 found no significant effect. The evidence base for all outcomes is small and preliminary.

Effective dose patterns: The one beneficial trial across all three outcomes consistently used 25 mL/day of flaxseed oil for 49 days. No other doses were associated with statistically significant benefits, and meta-analyses that included varied doses and forms of flaxseed showed neutral results.

Population insights: The only population in which statistically significant benefits were observed was adults with metabolic syndrome. Findings did not generalize to normotensive, hypertensive, or hemodialysis populations in meta-analyses.

Notable caveats: The entire evidence base consists of only 3 studies per outcome; many individual studies did not reach statistical significance; the beneficial effects may be smaller than they appear and may be limited to a specific form (flaxseed oil) and a specific population (metabolic syndrome patients).

Frequently asked

  • What is Flax good for according to research?
    Research suggests flaxseed oil may help reduce systolic blood pressure (2 of 3 studies show benefit) and possibly diastolic blood pressure and waist circumference, but the evidence is low to very low strength. Most positive findings come from a single trial in patients with metabolic syndrome.
  • What dose of Flax is typically used in studies?
    In the one trial that found significant benefits across multiple outcomes, the dose was 25 mL/day of flaxseed oil for 49 days. Other studies included in meta-analyses used varied forms and doses of flaxseed, and none of those showed statistically significant effects.
  • Who benefits most from Flax?
    The strongest (though still low-strength) evidence suggests that adults with metabolic syndrome may experience reductions in systolic blood pressure with flaxseed oil. Benefits were not observed in broader populations such as normotensive or hypertensive adults.
  • Are there caveats or limitations in the research on Flax?
    Yes. Each outcome is supported by only 3 studies (small evidence base), many did not reach statistical significance, and beneficial findings come from a single small RCT using a specific form (flaxseed oil) in a specific population. The evidence should be considered preliminary.
  • Does Flax help reduce waist circumference?
    One small RCT in 60 adults with metabolic syndrome found a statistically significant reduction in waist circumference using 25 mL/day flaxseed oil for 49 days. However, a meta-analysis and a review reported neutral or unclear effects, and overall evidence is very low strength.
  • Does Flax help lower blood pressure?
    For systolic blood pressure, 2 of 3 studies reported benefit, but evidence strength is low. For diastolic blood pressure, 1 of 3 studies reported benefit, also low strength. The beneficial effects were limited to one study using flaxseed oil in metabolic syndrome patients; other studies showed no significant effect.

Most-studied combinations with Flax

most supplement research is combination research
Also studied with:Olive Oil (2)

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