A diet rich in fish oil may reduce the likelihood of cancer cells spreading in the body under conditions of physical stress. Researchers at Tel-Aviv University drew this cautious conclusion from an animal study published recently in Clinical Nutrition.
If there are enough healthy natural killer cells present in the body, cancer cells stand little chance: natural killer cells annihilate them. But when the body is under heavy physical stress, for example after an operation, the concentration of natural killer cells decreases.
In healthy people the n-3 fatty acids in fish, such as DHA and EPA, have no effect on the immune system. But if you give these fatty acids to lab animals or humans who have undergone an operation, they prevent the number of immune cells from decreasing.
That’s why the Israelis wanted to know whether fish fatty acid could help improve the chances of cancer patients who undergo operations. They did experiments on mice and rats, giving them ordinary feed, feed containing 10 percent (per weight) n-3 fish fatty acids or 10 percent plant-based n-6 fatty acids.
The researchers injected B 16F 10.9 melanoma tumour cells into the paws of the lab animals. When the tumour was big enough the researchers removed it surgically. The figure below shows that the mice that had been given fish fatty acids had a higher survival rate after the operation than the animals in the other two groups.
In another experiment the researchers injected MADB106 lung cancer cells into the bloodstream of lab rats. Half of the rats had just undergone an abdominal operation [Surgery]. After 12 hours the researchers examined whether they could still detect cancer cells in the lungs [Lung tumor retention]. The figure above shows that fewer cancer cells were found in the lungs of the animals that had been given n-3 fatty acids in their feed.
The figures below may shed some light on how this happened: the cancer cells were attacked by natural killer cells. There were more of these present in the blood of the animals that had been given fish oil, and this was certainly the case after surgery.
The researchers suggest it is still too early to be able to issue advice for humans, saying more research must be done first. “Further experiments in rodents and ultimately well-designed clinical trials are necessary to determine whether fish oil feeding indeed normalizes Natural Killer cell function in cancer surgery, and more importantly, whether such an effect results in a lower tumor burden and mortality rate in the long term”, they conclude.