Patients receiving virtually all types of chemotherapy have been advised not to take fish oil supplements because they can make chemotherapy drugs ineffective, researchers from the University Medical Centre Utrecht, the Netherlands wrote in the journal Cancer Cell. Fish oils contain two fatty acids which make the tumors resistant to treatment. These fatty acids are also produced by stem cells in the blood, the authors add.
The authors explained that chemotherapy commonly loses its effectiveness over time, and scientists are not completely sure why this happens.
The Dutch researchers had been investigating how solid cancers (tumors) become resistant to treatments. In animal experiments, they found that the stem cells in the blood of mice responded to cisplatin, a commonly used cancer medication, by producing, two fatty acids.
The scientists referred to the fatty acids as PIFAs (platinum-induced fatty acids) – and identified them as 12-oxo-5,8,10-heptadecatrienoic acid (KHT) and hexadeca-4,7,10,13-tetraenoic acid (16:4(n-3)).
The two PIFAs trigger a series of chemical reactions which make cancerous cells resistant to a broad spectrum of chemotherapies.
They found that fish oil supplements as well as some algae extracts containing omega-3 and omega-6 fatty acids that are commonly bought off the shelf in supermarkets and health shops, would stop chemotherapy’s effects on some tumors in mice.
Cancer patients commonly take fish oil supplements in addition to their standard treatment.
The mice had tumors under the skin, which under normal conditions would shrink after the administration of chemotherapy. However, when they gave fatty acids to the mice, the tumors were unaffected by the chemotherapy and continued to thrive.
When medications which block the production of these fatty acids were used, the tumors’ resistance to chemotherapy went down, the authors wrote.
Lead scientists, Professor Emile Voest, an oncologist, 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.”
Written by Christian Nordqvist