A journal JAMA Oncology-published research has unveiled that certain fish oils and fish oil supplements may increase the risk for cancer patients by developing resistance to chemotherapy.

The researchers said the fish oils have been found to be having 16:4(n-3) in significant amount. It is a fatty acid having strong chemotherapy-negating effects that have been seen in pre-clinical models.

In an experiment, it has been found that low dose of fish oil interfered with chemotherapy activity in mice. Study’s co-author Dr. Emilie E. Voest with the Netherlands Cancer Institute in Amsterdam said that there is an increasing concern that use of supplements and anticancer drugs may have negative influence on the treatment result.

Two fatty acids 16:4(n-3) and 12S-HHT led to chemo-resistance in mice that had small quantities of the compounds. In the recent research, the researchers noted that volunteers who had the recommended daily dose of 10 milliliters of fish oil showed an immediate increase in 16:4(n-3) levels in their blood.

The level did not come to normal level until 8 hours after their ingestion. The researchers also came to know that consumption of 100 grams of herring or mackerel was linked with an increase in 16:4(n-3) blood levels and a smaller rise was seen with the consumption of salmon.

“Herein we show that fish oil contains substantial levels of 16:4(n-3), a fatty acid with potent chemotherapy-negating effects in preclinical models, and that intake of low doses of fish oil interferes with chemotherapy activity in mice”, said the authors.

Dr. Len Lichtenfeld, deputy chief medical officer at the American Cancer Society, affirmed that no clinical trial could be carried out to know whether or not fish oil stops chemotherapy’s effects in humans, as it would be unethical to evaluate the efficacy in patients.