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From the National Institutes of HealthNational Institutes of Health

Flaxseed oil


What is it?

Flaxseed is the seed from the plant Linum usitatissimum. Oil from the seed is used to make medicine.

Flaxseed oil is used for many conditions, but so far, there isn’t enough scientific evidence to determine whether or not it is effective for any of them. We do know, however, that it doesn’t seem to work for rheumatoid arthritis or for lowering elevated blood fats such as cholesterol and triglycerides.

In addition to treating rheumatoid arthritis and high blood fats, flaxseed oil is used for treating osteoarthritis, anxiety, benign prostatic hyperplasia (BPH), vaginal infections, dry eyes, “hardening of the arteries” (atherosclerosis), high blood pressure, heart disease, diabetes, and attention deficit-hyperactivity disorder (ADHD).

Some people use flaxseed oil as a laxative for constipation, for weight loss, and to prevent breast cancer and prostate cancer.

Flaxseed oil is also applied to the skin to sooth irritations or soften roughness.

In foods, flaxseed oil is used as cooking oil and in margarines.

In manufacturing, flaxseed oil is used as an ingredient in paints, varnishes, linoleum, and soap; and as a waterproofing agent.

How effective is it?

Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.

The effectiveness ratings for FLAXSEED OIL are as follows:

Possibly ineffective for...

  • High blood fats (hyperlipidemia). Some research shows that taking flaxseed oil does not significantly reduce cholesterol and triglyceride levels in people with high cholesterol and high triglycerides.
  • Rheumatoid arthritis (RA). Taking flaxseed oil daily for 3 months does not seem to improve symptoms of pain and stiffness, and has no effect on laboratory tests that measure severity of RA.

Insufficient evidence to rate effectiveness for...

  • Attention deficit-hyperactivity disorder (ADHD). There is some evidence that taking flaxseed oil might improve attention, impulsiveness, restlessness, and self-control in children with ADHD.
  • "Hardening of the arteries" (atherosclerosis). There is some evidence that increasing the amount of linolenic acid in the diet can help to prevent hardening of the arteries. Flaxseed oil contains linolenic acid, so some people suggest that flaxseed oil ought to prevent atherosclerosis. Though this assumption seems reasonable, there has been no research yet to prove it is correct.
  • Breast cancer. Research has shown that women who have higher levels of alpha-linolenic acid in their breast tissue are less likely to get breast cancer. Scientists think that high intake of linolenic acid might protect against breast cancer. Flaxseed oil is one source of linolenic acid, but it’s not known whether increasing flaxseed oil intake will actually help to prevent breast cancer.
  • Heart disease. There is evidence that people with existing heart disease, who get more alpha-linolenic acid from their diet, have a lower risk of dying from heart disease. Flaxseed oil is one source of alpha-linolenic acid, but research has not directly measured the effect of flaxseed oil intake on heart disease outcomes. It is also not known if flaxseed oil supplements have the same effects as flaxseed oil from food.
  • Diabetes. Research to date suggests that flaxseed oil doesn’t lower blood sugar in people with Type 2 diabetes.
  • Dry eyes. Some preliminary clinical research suggests that taking flaxseed oil might reduce irritation and symptoms of dry eyes. A specific product containing fish oil plus flaxseed oil (TheraTears Nutrition) might also reduce symptoms of dry eye and increase tear production.
  • High blood pressure. Early studies suggest that flaxseed oil supplements help to lower blood pressure in men with normal blood pressure, but high cholesterol. We’ll have to wait to see if flaxseed oil lowers blood pressure in people with high blood pressure.
  • Prostate cancer. Research studies don’t agree about the role of the flaxseed oil ingredient, alpha-linolenic acid, in prostate cancer. Some epidemiologic research suggests that high dietary intake of alpha-linolenic acid is linked with an increased risk for prostate cancer. Other research suggests high intake or high blood levels of alpha-linolenic acid is not linked with the overall risk of prostate cancer; however, extra alpha-linolenic acid might make existing prostate cancer worse. The source of alpha-linolenic acid appears to be important. Alpha-linolenic acid from dairy and meat sources has been positively linked with prostate cancer. Alpha-linolenic acid from plant sources, such as flaxseed or flaxseed oil, does not affect prostate cancer risk.
  • Anxiety.
  • Constipation.
  • Cancer.
  • Vaginal problems.
  • Weight loss.
  • Other conditions.
More evidence is needed to rate flaxseed oil for these uses.

How does it work?

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Flaxseed oil is a source of polyunsaturated fatty acids such as alpha-linolenic acid. The alpha-linolenic acid and related chemicals in flaxseed oil seem to decrease inflammation. That is why flaxseed oil is thought to be useful for rheumatoid arthritis and other inflammatory (swelling) diseases.

Are there safety concerns?

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Flaxseed oil is LIKELY SAFE for most adults when used appropriately short-term.

Large doses of 30 grams per day and higher can cause loose stools and diarrhea. Allergic reactions have occurred while taking flaxseed oil.

Some men worry that taking flaxseed oil might increase their chance of getting prostate cancer because of the alpha-linolenic acid that flaxseed oil contains. Researchers are still trying to figure out the role of alpha-linolenic acid in prostate cancer. Some studies suggest that alpha-linolenic acid may increase risk or make existing prostate cancer worse, but other studies find no connection. Nevertheless, the alpha-linolenic acid in flaxseed oil doesn’t seem to be a problem. Alpha-linolenic acid from plant sources, such as flaxseed, does not seem to affect prostate cancer risk, although alpha-linolenic acid from dairy and meat sources has been linked in some studies with prostate cancer.

Not enough is known about the safety of flaxseed oil when it is applied to the skin.

Special precautions & warnings:

Pregnancy: Flaxseed oil is POSSIBLY UNSAFE in pregnancy. Some research suggests that flaxseed oil might increase the change of premature birth when taken during the second or third trimesters of pregnancy. Pregnant women should avoid taking flaxseed oil.

Breast-feeding: There isn’t enough reliable information available about the safety of flaxseed oil during breast-feeding. Stay on the safe side and avoid using flaxseed oil while breast-feeding until more is known.

Bleeding disorders: Flaxseed oil might increase the risk of severe bleeding in patients with bleeding disorders. Talk to your healthcare provider before using flaxseed oil if you have a bleeding disorder.

Surgery: Flaxseed oil might increase the risk of bleeding during and after surgery. Stop using it at least 2 weeks before a scheduled surgery.

Are there interactions with medications?

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Moderate

Be cautious with this combination.

Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs)
Flaxseed oil might slow blood clotting and increase bleeding time. Taking flaxseed oil along with medications that also slow clotting might increase the chances of bruising and bleeding.

Some medications that slow blood clotting include aspirin, clopidogrel (Plavix), diclofenac (Voltaren, Cataflam, others), ibuprofen (Advil, Motrin, others), naproxen (Anaprox, Naprosyn, others), dalteparin (Fragmin), enoxaparin (Lovenox), heparin, ticlopidine (Ticlid), warfarin (Coumadin), and others.

Minor

Be watchful with this combination.

Medications that lower blood pressure (Antihypertensive drugs)
Flaxseed oil might lower blood pressure. Combining flaxseed oil with other drugs that lower blood pressure might increase the chance of blood pressure going too low.

Some medications that lower blood pressure include captopril (Capoten), enalapril (Vasotec), losartan (Cozaar), valsartan (Diovan), diltiazem (Cardizem), Amlodipine (Norvasc), hydrochlorothiazide (HydroDIURIL), furosemide (Lasix), and many others.

Are there interactions with herbs and supplements?

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Herbs and supplements that lower blood pressure
Flaxseed oil might decrease blood pressure. Combining flaxseed oil with other herbs and supplements with that lower blood pressure might make blood pressure go too low. Some of these herbs and supplements include andrographis, casein peptides, cat's claw, coenzyme Q-10, fish oil, L-arginine, lycium, stinging nettle, theanine, and others.

Herbs and supplements that might slow blood clotting
Flaxseed oil can increase the amount of time it takes for blood to clot. Taking it along with other herbs and supplements that slow blood clotting can slow blood clotting even more and could increase the risk of bleeding and bruising in some people. Some of these herbs include angelica, clove, danshen, garlic, ginger, ginkgo, Panax ginseng, and others.

Are there interactions with foods?

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There are no known interactions with foods.

What dose is used?

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The appropriate dose of flaxseed oil depends on several factors such as the user’s age, health, and several other conditions. At this time there is not enough scientific information to determine an appropriate range of doses for flaxseed oil. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using.

Note that flaxseed oil can easily break down chemically if exposed to light, heat, or air. Flaxseed oil should be stored in a frosted bottle and protected from heat. It can be stored in the refrigerator.

Other names

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Aceite de Linaza, Acide Alpha-Linolénique, Acide Gras Oméga 3, Acide Gras N-3, ALA, Aliviraaii, Alpha-Linolenic Acid, Alasi, Brown Flaxseed Oil, Brown-Seeded Flax Oil, Common Flax Oil, Echter Lein, Flachs, Flachssamen, Flax Oil, Flax Seed Oil, Golden Flax Oil, Graine de Lin, Huile de Lin, Kattan, Keten, Lin, Lin Commun, Lin Oléagineux, Linho, Lino, Lino Comune, Lino Mazzese, Lino Usuale, Linseed Flax Oil, Linseed Oil, Linum crepitans, Linum humile, Linum usitatissimum, Malsag, N-3 Fatty Acid, Oil of Flaxseed, Omega-3 Fatty Acid, Saatlein, Ta Ma, Tisii.

Methodology

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To learn more about how this article was written, please see the Natural Medicines Comprehensive Database methodology.methodology (http://www.nlm.nih.gov/medlineplus/druginfo/natural/methodology.html).

References

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To see all references for the Flaxseed oil page, please go to http://www.nlm.nih.gov/medlineplus/druginfo/natural/990.html.

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Last reviewed - 08/11/2011

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Page last updated: 27 September 2012