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Fish oils are NOT blood-thinners by Dr Neil McKinney, ND

Omega 3 oil is a marvelous natural anti-inflammatory and is also associated with positive changes in hypertriglyceridemia. These properties would be expected to give a great benefit in cardiovascular diseases (CVD). Somehow many doctors and scientists have attributed to fish oils the property of anti-coagulation. Thinning of the blood would be of concern if the patient is on blood-thinning drugs, has had hemorrhagic disorders, or is about to have surgery.

Scientists from Holland looking at the health of Inuit and Eskimo in the 1970s found low rates of CVD, and attributed this largely to intake of fish and blubber (seal, walrus and whale). This indigenous diet provided a very high intake of omega 3 oils. Fish are abundant all over the planet, so subsequent research focused on fish oils. However, after decades, and thousands of publications later, no dose of any type of fish oil was found to reproduce this “Eskimo Effect”. In time, the whole idea of this CVD protective effect fell into disrepute. Still, the common belief in the blood-thinning impact of omega 3 oils persisted with little controversy.

I was lecturing at a hospital in Philadelphia and suggested that fish oils should be avoided before surgery to lower risk of hemorrhage. An oncologist jumped up and challenged this, with an unassailable explanation. In their five Cancer Treatment Centers of America hospitals, for a year, they gave various doses of various fish oils to many hundreds of patients.  In no case were they able to detect any hint of an alteration of clotting by any of known blood tests, including the international normalized ratio (INR). I was kindly provided a PowerPoint presentation they use to train their cancer surgeons, indicating this fear of fish oils thinning the blood is a myth.

In this 2018 article by Akinoye, we see the peer-reviewed publication of results from a randomized trial that really should settle this matter. Furthermore, the researchers demonstrated a potential benefit in reduced need for transfusions in those with the highest blood levels of omega 3 oils on the morning of their surgery. They arrived at this important conclusion: “These novel findings support the need for reconsideration of current recommendations to stop fish oil or delay procedures before cardiac surgery.”


Akinoye, E., et al. Circ. Cardiovasc. Qual. Outcomes, 2018; 11.

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