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Ground Flaxseed for Cholesterol and Blood Pressure: What to Know

Ground flaxseed may modestly lower LDL cholesterol and blood pressure. Learn what trials found, how much people use, why grinding matters, and who should be careful.

Edited by Anmar ArabPublished 21 October 2026, 6 min read
On this page
  1. Quick answer
  2. What the research says
  3. How to use it
  4. Possible side effects and interactions
  5. Who should be careful
  6. When to see a doctor
  7. Frequently asked questions

Quick answer

Flaxseed, also called linseed, is the small brown or golden seed of the flax plant. It is rich in fibre, in a plant omega-3 fat called alpha-linolenic acid (ALA), and in plant compounds called lignans. It is widely promoted for heart health.

The evidence suggests that eating ground flaxseed every day may lower LDL ("bad") cholesterol a little and may bring blood pressure down in people whose blood pressure is high. The effects are modest, they seem to come from the seed rather than from flaxseed oil, and the studies vary a lot in size and quality.

Flaxseed is a sensible food to add to a balanced diet, but it is not a replacement for cholesterol or blood pressure medicine. Grind it, take it with plenty of fluid, and check with a pharmacist if you take blood thinners, diabetes medicine or blood pressure medicine.

What the research says

Cholesterol. The best-known summary is a 2009 meta-analysis in the American Journal of Clinical Nutrition by Pan and colleagues, which pooled 28 randomised controlled trials. Across all flaxseed products, total and LDL cholesterol fell only slightly (about 0.10 and 0.08 mmol/L). When the researchers looked at whole flaxseed on its own, the drop was larger: about 0.21 mmol/L for total cholesterol and 0.16 mmol/L for LDL. Flaxseed oil did not lower cholesterol significantly. The effects were clearer in women, especially after menopause, and in people who started with higher cholesterol. Flaxseed did not change HDL ("good") cholesterol or triglycerides.

These are small changes, so flaxseed is best seen as one helpful part of an overall diet rather than a treatment on its own. Mayo Clinic notes that daily flaxseed may help manage cholesterol when combined with exercise and a low-cholesterol diet.

Blood pressure. The most striking trial is the FlaxPAD study, published in Hypertension in 2013 by Rodriguez-Leyva and colleagues. It randomised 110 people with peripheral artery disease to 30 g of milled flaxseed or a placebo every day for six months. Systolic blood pressure ended up about 10 mmHg lower and diastolic about 7 mmHg lower in the flaxseed group. In people whose systolic pressure started at 140 mmHg or above, systolic pressure fell by about 15 mmHg. The effect was seen only in people with high blood pressure.

A 2024 meta-analysis in Clinical Nutrition Research (Fazeli Moghadam and colleagues) pooled five trials with 388 adults with high blood pressure. Flaxseed lowered systolic pressure by about 8.6 mmHg and diastolic by about 4.9 mmHg on average. However, the results varied widely between studies, the doses ranged from capsules of 500 mg to 36 g of seed a day, and when one study was removed the effect on systolic pressure was no longer statistically significant. Benefits appeared more consistent in trials lasting longer than 12 weeks. The authors called for larger, longer and better-quality trials before flaxseed can be recommended for high blood pressure.

What health authorities say. The US National Center for Complementary and Integrative Health (NCCIH) describes the research on flaxseed as being of varying quality and does not endorse it for any particular condition. Mayo Clinic says some research suggests flaxseed might help lower blood pressure, and that several studies found daily flaxseed lowered total and LDL cholesterol.

Why "moderate" evidence? There are many randomised trials, and the cholesterol findings are fairly consistent for whole seed, but the effects are small and the blood pressure trials are few, small and mixed.

How to use it

  • Choose ground (milled) flaxseed. Mayo Clinic explains that most nutrition experts prefer ground flaxseed because whole seeds may pass through the gut undigested, so you miss some of the benefit. You can buy it ready-milled or grind whole seeds at home in a coffee grinder or food processor.
  • Typical amounts. One tablespoon (about 7 g) of ground flaxseed provides roughly 2 g of fibre and 37 calories, according to Mayo Clinic. The FlaxPAD trial used 30 g a day, which is roughly four tablespoons. Start with a smaller amount and increase slowly.
  • Easy ways to eat it. Stir a tablespoon into porridge, cereal or yogurt, add it to smoothies, or bake it into bread, muffins and biscuits.
  • Drink enough fluid. As with other fibre sources, take flaxseed with plenty of water or other drinks.
  • Space it from medicines. Mayo Clinic advises not taking flaxseed at the same time as oral medicines. Ask your pharmacist how best to time it with your own medicines.
  • Seed, not oil, for cholesterol. Flaxseed oil provides ALA but lacks the fibre, and in the Pan meta-analysis it did not lower cholesterol.

Possible side effects and interactions

  • Digestive effects. Larger amounts, especially without enough fluid, can cause bloating, wind, fullness and diarrhoea.
  • Allergy. Allergic reactions to flaxseed are possible.
  • Raw or unripe seeds. NCCIH and Mayo Clinic both advise against eating raw or unripe flaxseed, which may contain potentially toxic compounds.
  • Blood thinners. Flaxseed, and especially flaxseed oil, may reduce blood clotting. Taking it with anticoagulant or antiplatelet medicines could raise the risk of bleeding. Mayo Clinic advises telling your healthcare team before surgery.
  • Blood pressure medicines. Flaxseed may add to their effect and lower blood pressure too far.
  • Diabetes medicines. Blood sugar may drop lower than expected.
  • Oestrogen-containing medicines. Mayo Clinic notes flaxseed may reduce the effect of oestrogens, including some contraceptive pills and hormone replacement therapy.
Do not stop or reduce prescribed cholesterol or blood pressure medicine because you have started eating flaxseed. If you take blood thinners, diabetes medicine, blood pressure medicine or hormonal medicines, talk to your doctor or pharmacist before eating flaxseed regularly.

Who should be careful

  • Pregnant or breastfeeding women. NCCIH says some studies suggest flaxseed may be unsafe in pregnancy, although the evidence is not conclusive, and little is known about safety while breastfeeding. Mayo Clinic advises against flaxseed products during pregnancy and breastfeeding.
  • People taking the medicines listed above.
  • People with a known flaxseed allergy.
  • Anyone due to have surgery, who should tell their surgical team.

When to see a doctor

Flaxseed is a food, not a test or a treatment plan. See a doctor or nurse:

  • to have your blood pressure and cholesterol checked and to agree a plan, rather than relying on flaxseed alone
  • if your home blood pressure readings are repeatedly high, or unusually low with dizziness or fainting after starting flaxseed alongside medicine
  • if you notice unusual bruising or bleeding while taking a blood thinner
  • if you develop hives, swelling of the face or lips, or trouble breathing after eating flaxseed (call emergency services if breathing is affected)
  • if you have chest pain, sudden severe headache, weakness on one side of the body or trouble speaking (call emergency services)

Frequently asked questions

Is flaxseed oil as good as ground flaxseed?

Not for cholesterol. In the Pan meta-analysis, whole flaxseed lowered cholesterol slightly, but flaxseed oil did not. The oil still contains ALA omega-3, but none of the fibre.

How long does flaxseed take to work?

In the main trials, people ate flaxseed daily for several months. In the 2024 blood pressure meta-analysis, effects were more consistent in studies lasting longer than 12 weeks, so a few days is unlikely to make a measurable difference.

Can flaxseed replace my blood pressure tablets?

No. The reductions seen in studies were modest and inconsistent, and stopping prescribed medicine can be dangerous. Flaxseed may be added to a healthy diet alongside treatment, after checking with your doctor or pharmacist.

Is flaxseed a good source of omega-3?

Yes, of the plant kind. NCCIH notes that flaxseed and flaxseed oil contain alpha-linolenic acid (ALA), an omega-3 fat. This is a different form from the omega-3 fats found in oily fish.

References

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