Could Fish Oil Cause Chemo-Resistance in Cancer Patients?

Consuming certain fish oils, as well as herring and mackerel, could increase the risk of chemotherapy-resistance in cancer patients, according to a recent study.

“Our research group previously identified specific endogenous platinum-induced fatty acids (PIFAs) that, in picomolar quantities, activate splenic macrophages leading to resistance to chemotherapy in mouse models. Fish oil was shown to contain the PIFA 16:4(n-3) (hexadeca-4,7,10,13-tetraenoic acid) and when administered to mice neutralized chemotherapy activity,” said the study’s authors.
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“Because patients with cancer frequently use fish oil supplements, we set out to determine exposure to 16:4(n-3) after intake of fish or fish oil,” they said.

For the study, 118 patients were surveyed to determine their use of fish oil supplements and intake of fish; researchers evaluated 3 brands of fish oil and 4 species of fish.

Overall, 11% of respondents reported omega-3 supplement use. For each fish oil tested, researchers found relevant amounts of 16:4(n-3) out of 0.2 to 5.7 uM.

When researchers administered 10ml (the recommended daily amount) to 30 healthy participants, they observed a rise in plasma 16:4(n-3), which reached up to 20 times the baseline levels. Consumption of herrin and mackerel yielded similar increases in plasma 16:4(n-3).

Because 16:4(n-3) has been shown to interfere with chemotherapy, and ingestion of omega-3 supplements led to such significant increases in plasma 16:4(n-3), the investigators urged that until further data is made available, fish and fish oil with high amounts of 16:4(n-3) should be avoided on the days before and after chemotherapy.

The complete study is published in the April issue of JAMA Oncology.

-Michelle Canales Butcher

Reference:

Daenen LG, Cirkel GA, Houthuijzen JM, et al. Increased plasma levels of chemoresistance-inducing fatty acid 16:4(n-3) after consumption of fish and fish oil. JAMA Oncol. 2015 April [epub before print] doi:10.1001/jamaoncol.2015.0388.