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Chemotherapy Patients Should Not Take Fish Oil: New Study

Chemotherapy drugs

You have probably heard about the health benefits of fish oil, but a new study warns cancer patients about an important downside. Researchers in the Netherlands have advised chemotherapy patients to avoid taking fish oil supplements because they can make the chemotherapy drugs ineffective.

Cancer patients frequently take fish oil supplements

Although fish oil is perhaps best known for its anti-inflammatory properties, it’s also been shown to have a role in cancer. One recent study published by the American Association for Cancer Research, for example, indicated that fish oil may help prevent breast cancer. Another study, from the University of Michigan, suggested that excessive fish oil could increase the risk of colon cancer.

Now it appears that fish oil could have an impact on cancer in another way. Investigators from the University Medical Centre Utrecht, the Netherlands, report that fish oils contain two platinum-induced fatty acids (PIFAs) known as KHT (12-oxo-5,8,10-heptadecatrienoic acid) and 16:4(n-3) (hexadeca-4,7,10,13-tetraenoic acid) that are involved in making cancer cells resistant to a wide variety of chemotherapy drugs. Stem cells in the blood also produce these fatty acids.

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The Dutch researchers conducted mouse experiments and found that fish oil as well as some algae extracts that contained omega-3 and omega-6 fatty acids stopped the effects of chemotherapy on some tumors in mice. However, when the mice were given drugs to block the production of the fatty acids, their tumors became less resistant to chemotherapy.

This finding has led the authors to advise patients who are receiving chemotherapy to not take fish oil, which is a common nutritional supplement among cancer patients. One benefit of fish oil in these patients is that it helps maintain and even regain loss muscle mass, according to a recent study published in Cancer. Loss of muscle and fat in cancer patients can hinder their response to cancer therapy.

According to oncologist Emile Voest, the lead scientist, “we show that the body itself secretes protective substances into the blood that are powerful enough to block the effect of chemotherapy,” and that “these substances can be found in some types of fish oil.” While further investigations are done into this phenomenon, they recommend that cancer patients not take fish oil supplements while undergoing chemotherapy.

American Association of Cancer Research
Murphy RA et al. Cancer 2011 Apr 15; 117(8): 1775-82
Roodhart JML et al. Cancer Cell 2011 Sep; 20(3): 370-83

Picture credit: Wikimedia Commons