cod liver oil side effects

Cod Liver Oil Side Effects

Cod liver oil is the essential oil extracted from the livers of Atlantic cod. Scientists discovered that cod liver oil helped eradicate rickets, a common disease in 17th century England and in the U.S. through the 1920’s.  Back then, cod liver oil was known to be rich in vitamins A and D only but its strong therapeutic properties are still being discovered today. Rickets was eradicated in the 1930’s and today cod liver oil is used successfully to treat many nutrient deficiencies.naturalvitamins

Nordic countries regularly consume cod liver oil to protect themselves from nutrient deficiencies. Studies have shown that taking one to two teaspoons of cod liver oil daily can help reduce the risk of cancer, diabetes, kidney problems, inflammatory bowel disease, high cholesterol and joint pain. Seems like a supplement worth taking, but some have expressed concern over the consumption of cod liver oil.  Is it all it’s cracked up to be? Are there any cod liver oil side effects you should be aware of? Let’s look a little deeper into cod liver oil research and see what it reveals.

Difference between Cod Liver Oil and Fish Oilfish oil

Cod liver oil is oil that is extracted solely from the livers of cod fish. Fish oil is oil extracted from the tissue of deep sea oily fish like tuna, mackerel, herring, salmon, cod, and trout. Cod liver oil contains fewer Omega 3 fatty acids than regular fish oil but contains more nutrients like vitamin D and A.

What Are The Researched Benefits Of Cod Liver Oil?

cod liver oil

Cod liver oil is an anti-inflammatory food due to its omega 3 fatty acid profile and it’s high levels of vitamins A and D.  Both of these nutrients help fight inflammation and build the immune system which is critical in so many inflammatory conditions including inflammatory bowel diseases.

  • Cod liver oil is a good type of fat. Omega 3 fatty acids help break down carbohydrates when eaten with a meal to reduce the blood sugar rise in your bloodstream.
  • The nutrients in cod liver oil, mostly vitamin A and E help reduce the risk of macular degeneration.  Macular degeneration can lead to blindness and is on the rise in the U.S.
  • Cod liver oil contains high amounts of vitamin D and can help with cognitive performance.
  • The vitamin A and D in cod liver oil can help heal IBD and other digestive disorders.
  • The vitamin D in cod liver oil can help reduce the progression of cancer by slowing the growth and development of new blood vessels in cancerous tissue.
  • Cod liver oil was shown to protect against bone loss, obesity and resulted in a greater bone turnover. (Bone. 2008 May;42(5):996-1003).
  • Cod liver oil has anti-depressant properties and is associated with a lower rate of depressive symptoms for the general population. (J Affect Disord. 2007 Aug;101(1-3):245-9).

Any Side Effects From Cod Liver Oil?

Cod liver oil is generally well-tolerated and safe.  But there are a few things you should be aware of.cod-liver-oil-side-effects-1

  1. The most common complaint is a fishy aftertaste. To reduce this, take your cod liver oil with food and avoid taking it right before bedtime.
  2. If you have a bleeding disorder or are taking blood-thinning medications, talk to you doctor before taking cod liver oil.  Cod liver oil can thin the blood and cause bleeding issues.  For this reason, you would also want to stop taking cod liver oil about a week before any surgeries.
  3. These drugs interact with cod liver oil.  Talk to your doctor.


4)  A study done on rats in the “Journal of Diabetes and Metabolic Disorders” in February 2013 found that cod liver oil may raise blood sugar in diabetics.  An explanation of why this might be was provided by the University of Maryland Medical Center. Their claim is that the body converts fatty acids into sugars which may explain the rise in blood sugar.  If you are a diabetic, take cod liver oil or any fish oil under the care of your healthcare practitioner.

Recent Controversy Surrounding Cod Liver Oil

vitamin A toxicity

Dr. Joseph Mercola recently withdrew his recommendations for taking cod liver oil. His claim is that the cod liver oil of today has the wrong ratios of vitamin D and Vitamin A.  According to him, modern processing for contaminant removal decreases the vitamin D level in the cod liver oil, thus making the vitamin A more toxic to the body.  High amounts of vitamin A are toxic to the body and vitamin A needs vitamin D to buffer this.  

The Weston Price Foundation rebutted his article claiming that Dr. Mercola’s arguments were not sound and that purchasing cod liver oil with the right ratios is still possible.  You can read the response here.

Consumer watchdog agencies have found that many cod liver oil manufacturers do not have the right levels of vitamin A and D, so finding the best sources is very important.

Click here for a list of cod liver oil supplements with the right ratios of vitamin A and D.


Cod liver oil has been used for hundreds of years to treat rickets and nutrient deficiencies.  Taking cod liver oil during the winter months when sunlight is scarce provides people with adequate levels of vitamin D and A.  

Cod liver oil is rich in Omega 3 fatty acids and provides anti-inflammatory effects to the body resulting in lower incidences of cancer, bone loss, cognitive decline, Irritable Bowel Disease (IBD), depression among other health challenges.

There has been controversy surrounding the nutrient levels and toxicity of Vitamin A and the manufacturing processes of cod liver oil possibly doing more harm than good.  This has been refuted by other experts, but the importance of taking a reputable product with the right nutrients is very important.  Click here for a list of reputable sources of cod liver oil.

Hope you enjoyed this article and please comment below!  I love to hear from you.

14354940_1147966088611029_3013149574780621067_n(4)Linda Watson is a certified Functional Health Coach

4 Comments Add yours
  1. As a nurse, I think it is really important to use supplements in our every day routines. We are so overmedicated in our country and so many diseases could be solved by changing our lifestyle habits! I actually work with cancer patients administering chemotherapy and I thought it was fairly interesting how many chemotherapy drugs interact with cod liver oil. I am very thankful for reading your article so I can make sure to educate my patients who are on xeloda and 5FU to not be taking their cod liver oil while on treatment! My only issue with the fish oils is that aftertaste :/ but I shouldn’t let that stop me from taking it.

  2. You and this post are awesome! Thanks so much for helping to clear things up and for giving an in depth background on this supplement that has been used for so long. I used to take cod liver oil regularly but in the past 2 years have transitioned from pescetarian to vegetarian. Do you happen to know of any alternative for vegetarians?

    1. Hi Manika! Yes I do actually. I will also make another post for those that are vegetarian. In the meantime, try this one. Hawaiian Spirulina
      The spirulina has the omega 3′ like cod liver oil, I would take a vitamin D supplement to go along with it since spirulina is a good source of vitamin A and A balances D and vice versa.

Leave a Reply

Your email address will not be published. Required fields are marked *