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Moderate evidenceGut health

Ground Flaxseed

A food, not really a supplement: ground flaxseed supplies viscous fiber, ALA and lignans. Randomized trials support modest benefits for constipation, blood pressure and blood lipids.

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What the science says

  • Constipation Moderate evidence

    A randomized trial in a Chinese population found flaxseed supplementation improved functional constipation and quality of life, and smaller randomized trials in constipated patients with type 2 diabetes reported similar results, with flaxseed performing comparably to psyllium.

  • Blood pressure Moderate evidence

    A meta-analysis of randomized controlled trials found flaxseed lowered blood pressure in hypertensive subjects by a few mmHg, an effect that is real but small.

  • Blood lipids Moderate evidence

    A dose-response meta-analysis of randomized trials in people with dyslipidemia-related conditions found small reductions in LDL and total cholesterol, with whole ground seed performing better than flaxseed oil for lipids.

Dosage & safety

Studied doseStudies commonly used 10–30 g per day of ground seed (about 1–3 tablespoons), taken with plenty of water. Whole seeds pass through largely intact — grind them, and store the meal in the fridge.
SafetyGas and bloating are common when starting. Take with fluid; very high intakes can worsen obstruction in people with strictures. The lignans are weakly estrogenic — discuss with a doctor if you have hormone-sensitive cancer. Flaxseed may add to the effect of blood-pressure and blood-thinning medication, and can slow absorption of drugs taken at the same time.

How to take it

TimingTiming does not matter.
With food?With food and plenty of water.
Worth knowingGrind it fresh or keep pre-ground meal in the fridge, because the oils go rancid quickly.

Interactions

With medications

  • warfarin and other anticoagulants or antiplatelets

    High intakes may modestly add to the bleeding tendency. keep intake steady and tell your doctor you take it

  • blood pressure medication

    Flaxseed lowers blood pressure slightly, adding to the drug effect. monitor your blood pressure when starting

  • oral medications generally

    The soluble fiber can delay or reduce absorption of drugs taken at the same time. separate by at least 2 hours

With other supplements

  • fish oil, garlic and other blood-thinning supplements

    Small additive effects on platelet function and blood pressure. fine for most people, but avoid stacking before surgery

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does ground flaxseed help constipation?

Yes, with moderate evidence: randomized trials found ground flaxseed improved functional constipation, performing comparably to psyllium in constipated patients with type 2 diabetes.

Does flaxseed lower blood pressure and cholesterol?

Meta-analyses of randomized trials show ground flaxseed lowers blood pressure in hypertensive people by a few mmHg and modestly reduces LDL and total cholesterol. The evidence is moderate, but the effects are small.

How much ground flaxseed per day?

Studies used 10–30 g of ground flaxseed per day, about 1–3 tablespoons, with plenty of water. Whole seeds pass through largely intact, so grind them and keep the meal in the fridge.

Is flaxseed safe with blood thinners or blood pressure pills?

High flaxseed intakes may modestly add to bleeding tendency with warfarin and slightly lower blood pressure, so keep intake steady and tell your doctor. Separate other oral drugs from flaxseed by at least 2 hours.

Scientific references

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