Healthy living

Fish oils undermine chemotherapy

Fish oils inhibit cancer chemotherapy Reduce effectiveness of cancer treatment

Cancer patients should avoid taking fish oil supplements as they may reduce the effectiveness of chemotherapy drugs, scientists have warned.

Researchers at the University Medical Center Utrecht discovered that certain fatty acids found in fish oils can make cancer cells resistant to nearly all types of chemotherapy.

Chemotherapy often becomes less effective over time, but in many instances it is unclear how or why this happens.

It now appears that two types of fatty acid that are made by stem cells in the blood makes cancer cells resistant to the effects of chemotherapy.

Scientists made the discovery after looking at how tumours in mice become resistant to chemotherapy drugs.

Normally, treating the animals with cisplatin, a common chemotherapy drug, would cause the tumours to shrink. But if the mice were given fatty acids, the tumours were resistant to the treatment.

Stem cells in the blood were found to be the source of the two fatty acids, which the researchers called PIFAS (platinum-induced fatty acids).

Scientists also discovered that stem cells in the blood of patients produce the fatty acids that desensitize tumours to a broad spectrum of chemotherapy drugs.

However, the researchers warned that the fatty acids can also be found in fish oil supplements as well as in some algae extracts.

The findings showed that commercially available fish oil supplements could also make some mouse tumours resistant to chemotherapy.

Many cancer patients often use such supplements in addition to their standard medical treatment, the researchers said.

Study leader Professor Emile Voest, a medical oncologist at UMC Utrecht, said: "Where resistance to chemotherapy is concerned, we usually believe that changes in the cancer cells themselves have occurred.

"Now we show that the body itself secretes protective substances into the blood that are powerful enough to block the effect of chemotherapy.

"These substances can be found in some types of fish oil. Whilst waiting for the results of further research, we currently recommend that these products should not be used whilst people are undergoing chemotherapy."

The study is to be published in the journal Cancer Cell.

This article was published on Tue 13 September 2011

Image © Alexander Raths -

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