9 Flaxseed Oil Side Effects and How to Avoid Them

flaxseed oil side effectsAre you thinking about adding flaxseed oil to your diet but are worried about flaxseed oil side effects?

We’ll review the 3 main thing to be concerned about….

As a popular healthy oil, it’s a plant-based source of the omega 3 fatty acid, alpha linolenic acid.

These healthy fats have been shown in research to help reduce inflammation, lower your risk for blood clots and may improve mood and learning function in children.

However, while it does have many health benefits there is actually a small risk for possible side effects.

So here are the 3 main areas to be concerned about if using this healthy oil:

  1. Health risks from getting too much alpha linolenic acid (ALA)
  2. Possible hormonal effects from the phyto-estrogens in flaxseeds
  3. Bleeding risks from excessive omega 3 fatty acids


Possible Health Risks and Side Effects from Using Flaxseed Oil:

The very first time I started using flaxseed oil, I thought that it was generally safe to use and I didn’t think twice about side effects. However, further research shows that there is a possible risk for flaxseed oil side effects.

1. Flaxseed Oil may cause an Increased Risk for Breast Cancer:

  • There’s actually conflicting reports on this topic as some studies show an increased risk of breast cancer from consuming high amounts of alpha linolenic acid (ALA) and other studies show the ALA protects against breast cancer.
  • A study done in Toronto, Canada found women awaiting breast cancer surgery had slower growing breast tumors when they ate muffins with 25 grams of ground flaxseeds.

2. Flaxseed Oil may Affect Blood Clotting:

  • Some researchers believe flaxseed oil may affect certain blood clotting factors which can make your blood thinner. 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. Pregnancy Risks:

  • Studies show that the hull of the flaxseed contains an active phyto-estrogen called lignans. Lignans are a plant-based estrogen which scientists believe can encourage menstruation which may be harmful to your pregnancy. Some animal studies that found large consumption of flaxseeds might affect the reproductive system. If you’re pregnant, or planning on becoming pregnant, you should consult with your Obstetrician before using flaxseed.

4. Effects on Breastfeeding:

  • Researchers are also unsure of these phyto-estrogens effects on 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 the flaxseed oil side effects in children and infants. I started giving my son flaxseed oil mixed into fruit smoothies when he was 3 years old and I didn’t experience any issues.  However, if your child has suspected food allergies you may wish to consult with your child’s pediatrician before giving flaxseed oil to them.

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:

  • A study from Spain found some people with allergies to linseed oil experienced 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 ‘cold’ oil and should always used at room temperature or cold. I usually store my bottle of flaxseed oil in the fridge after opening. I believe most flaxseed manufacturers also recommend the bottle be stored in the fridge after you open it.
  • 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 oil side effectsAlthough there aren’t many documented studies on flaxseed oil’s side effects, it pays to be cautious with any natural supplement.

You can avoid these side effects by using common sense. Consult your health care provider if your have specific medical conditions that need to be addressed.

As long as flaxseed oil is not used excessively or abused, I think it’s a healthy oil that can supply your diet with the essential fatty acids it needs.


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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