List of Flaxseed Oil Side Effects and How to Avoid Them

flaxseed oil in bottles and soft gels beside wooden spoon with whole flaxseeds

Many natural health advocates emphasize the importance of eating a healthy diet consisting of plant-based foods, whole grains, legumes, seeds and nuts.

Flax seeds are gaining popularity as a ‘super food’ due to ongoing research uncovering their many health benefits.

Not only are flax seeds a source of protein and carbohydrates, they are also high in the omega 3 fatty acid, alpha linolenic acid (ALA), fiber and lignans.  Lignans may have anti-cancer properties due to their estrogenic properties..

Some of the health benefits of omega 3 fatty acids include enhancing a baby’s brain health during pregnancy, reducing inflammation and lowering your risk for blood clots.

Due to the flax seed’s impressive nutritional profile, it’s no surprise that flaxseeds oils are growing in popularity with health conscious consumers.

However, flax seeds and flaxseed oil may cause specific side effects due to their unique nutritional profile:

  1. Risk for bleeding disorders from excessive omega 3 fatty acids
  2. Possible hormonal effects from the lignans found in flax seeds

Possible Health Risks and Side Effects from Flaxseed Oils

bottle of organic flaxseed oil side effects

As discussed in our Consumer’s Guide to Buying the Best Flaxseed Oil, these products are available in soft gel capsules and bottled liquids.

You can also get flaxseed oils blended with flax seed particulates which will provide lignans, as well as other additional ingredients.

The following list includes possible side effects and risks from using flax seeds, flaxseed oil (with and without lignans) and intake of the omega 3 fatty acid, alpha linolenic acid (ALA) .

This information is not to be construed as Medical advice – please consult with your Doctor or Health Care provider before using any nutritional supplement.

1. Flaxseed Oil may Inhibit Blood Clotting:

  • Consumers using blood-thinning medications need to be aware that ALA inhibits arterial thrombus formation.  Consumption of flaxseed oil may affect certain blood clotting factors which could make some individuals more at risk for bleeding disorders.  If you’re taking blood thinning medications, such as Coumadin, Heparin or even aspirin, you should consult with your doctor before adding flaxseed oil to your diet.

3. Estrogens in Flaxseed Oil Lignans May Pose Pregnancy Risk:

  • Researchers claim that flax seeds and their lignan extracts appear to be safe for adults, however, some animal studies suggest that pregnant women limit or avoid flax seeds and flaxseed oil with lignans.
  • A study showed flax seeds fed to pregnant rats affected the reproductive development of their offspring.
  • Another animal study showed that a maternal flax seed diet during pregnancy or lactation increased the risk for carcinogenic mammary tumors – possibly due to the effect of flax seed on circulating estrogen levels.
  • If you’re pregnant, or planning on becoming pregnant, you should consult with your Obstetrician before using flaxseed oils.

4. Effects on Breastfeeding:

  • Researchers are also unsure of the lignan’s phyto-estrogens may effect nursing babies. There are currently no studies in this area so it would be best to be cautious and avoid using flaxseed oil while breastfeeding.  Consult your doctor before taking flaxseed oil while breastfeeding.

5. Giving Flaxseed Oil to Young Children:

  • There are no documented studies on any flaxseed oil side effects in children and infants. However, if your child has suspected food allergies you may wish to consult with your child’s pediatrician before administering flaxseed oil.

6. Don’t Apply Flaxseed Oil to your Eyes, Open Sores or Wounds:

  • Flaxseed oil is safe to eat, but it’s advised to avoid putting the oil into any open wounds and sores to prevent possible reactions.

7. Eating Too Much Flaxseed Oil may Cause an Upset Stomach and Diarrhea:

  • The average dosage is usually a 1000 mg soft gel or a single tablespoon of flaxseed oil. If you insist on using more, try to slowly increase your dosage to avoid possible gastro-intestinal side effects such as upset stomach, gas or bloating.

8. Avoid taking Flaxseed oil if you’re Allergic to Flaxseed or Linseeds:

  • Although rare, there are cases of people experiencing severe allergic reactions to flaxseed oil. People with allergies to linseed oil may experience hives, watery eyes, diarrhea, shortness of breath, stuffed up nose, and other allergic reactions.

9. Never Heat or Cook Flaxseed Oil:

  • Flaxseed oil is a naturally unrefined oil, normally produced with minimal heat exposure.
  • Exposing the oil to high heat could damage the fragile fatty acids which may cause the oil to become rancid or create excessive fatty acid free radicals.

Flaxseed oils are generally regarded as safe. It’s a healthy oil that is well-suited for consumers seeking a plant-based source of omega 3 fatty acids.

Flaxseed oil side effects are  rare and can usually be avoided if consumers are aware and diligent about its ingredients and how they use it.

 Consult your health care provider if your have specific medical conditions that need to be addressed.

Research References:

Dietary flaxseed alters tumor biological markers in postmenopausal breast cancer. Thompson LU, Chen JM, Li T et al. Department of Nutritional Sciences, Princess Margaret Hospital, University of Toronto, Canada Clinical Cancer Research. 2005 May 15;11(10):3828-35.

Influence of n-3 fatty acids on the growth of human breast cancer cells in vitro: relationship to peroxides and vitamin E. Chajes V, Sattler W, Stranzl A, Kostner GM. Institute of Medical Biochemistry, University of Graz, Austria. Breast Cancer Research & Treatment 1995;34:199–212.

Flaxseed and its lignan and oil components reduce mammary tumor growth at a late stage of carcinogenesis. Thompson LU, Rickard SE, Orcheson LJ, Seidl MM. Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Canada. Carcinogenesis 1996;17:1373–6.

Flaxseed and its lignan precursor, secoisolariciresinol diglycoside, affect pregnancy outcome and reproductive development in rats. Tou JC, Chen J, Thompson LU. Department of Nutritional Sciences, University of Toronto, Canada. The Journal of Nutrition 1998;128:1861–8.

Alpha-linolenic acid content of adipose breast tissue: a host determinant of the risk of early metastasis in breast cancer. Bougnoix P. Breast Journal Cancer 1994;70:330–40.

Anaphylaxis caused by linseed (flaxseed) intake. Alonso L, Marcos ML, Blanco JG, et al. Seccion Alergologia, Hospital General Yague, Burgos, Spain. The Journal of Allergy & Clinical Immunology 1996;98:469–70.

Mutagens from heated Chinese and U.S. cooking oils. Shields PG, Xu GX, Blot WJ, et al. Laboratory of Human Carcinogenesis, National Cancer Institute, Bethesda, Md USA. Journal of National Cancer Institue 1995;87:836–41.

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