By Katherine Ip
Fish oil is a well-known dietary supplement that is likely to reduce the risk of getting heart disease. More research is needed to find out if it may also reduce high blood pressure, menstrual pain, the risk of stroke, and the symptoms of arthritis, bipolar disorder and ADHD. 
Some studies have suggested that fish oil and the omega-3 fatty acids it contains might also help improve the effectiveness of chemotherapy for cancer patients, while reducing the bad side effects. The types of chemotherapy tested include anthracyclines, cisplatin, irinotecan, and alkylating agents. Only two studies were done on humans, and the others were done on animals or cancer cells in test tubes.
Fish Oil Supplements, Lung Cancer, and Chemotherapy
Late-stage non-small cell lung cancer (NSCLC) is usually treated with chemotherapy, but chemotherapy is often ineffective. And, the current treatments have very unpleasant side effects that can severely harm the quality of a patient’s life, so researchers are always looking for ways to minimize damage to the body’s healthy cells while still attacking cancer cells with full force.
In 2011, a very small study by researchers from Canadian Universities looked at whether fish oil could help chemotherapy patients with non-small cell lung cancer (NSCLC) that has spread to the lymph nodes or to other parts of the body (Stage III and Stage IV). Patients with these late stages of lung cancer, on average, only live about 2 years after being diagnosed.
Since the cancer had already spread, all the patients were given the same palliative chemotherapy, aimed at reducing cancer symptoms and improving the patient’s quality of life, rather than curing the patient. Researchers only included lung cancer patients who had never had chemotherapy before. Only 15 of the patients were given fish oil and 31 were not. When they started their chemotherapy, the patients in the group taking fish oil had a choice of taking four capsules a day (each with 1 gram of fish oil), or 7.5 milliliters of actual fish oil, which provides the same amount of omega-3 fatty acids.
How did Fish Oil Affect Survival?
The patients who took fish oil responded much better to chemotherapy than those who didn’t. Their tumors shrank more in size or shrank more quickly, and they were almost twice as likely to be alive a year after treatment compared to the patients who didn’t take fish oil (60% compared to 39%). These results held true regardless of how old the patient was, whether the patient was a man or woman, and how much muscle mass the patient had. The latter is important because patients with lower muscle mass tend to suffer from more negative side effects from chemotherapy.
Patients who did not take fish oil were more likely to have their cancer get worse after two cycles of chemotherapy than patients who took fish oil. And, more of the patients who took fish oil were able to complete all of their planned chemotherapy, because they experienced less side effects for the same levels of chemotherapy as patients who did not take fish oil. Since the patients who took fish oil felt well enough to receive more cycles of chemotherapy, their tumors also shrank more and they lived longer.
Did Fish Oil Affect Quality of Life?
When chemotherapy kills the body’s healthy cells (think of it like “friendly fire”), it can cause side effects such as nausea, vomiting, and constipation, and it also lowers the body’s ability to fight infection. Since the patients taking fish oil were able to complete more cycles of chemotherapy, we would expect them to have worse side effects. Instead, the side effects listed above were about the same for patients taking fish oil and those that did not. The researchers suspect that the reason why is that fish oil protected the healthy cells from the chemotherapy, but not the cancer cells. Their findings are consistent with a study where mice with lung cancer responded better to treatment when fed fish oil. They are also consistent with a study in which breast cancer patients responded better to chemotherapy when their breast tissue had a higher concentration of DHA, one of two fatty acids found in fish oil.
Is There a Catch?
The study of fish oil and lung cancer included only 31 patients not taking fish oil and 15 patients taking fish oil. Such a small study does not provide adequate evidence, but it does mean more research is warranted.
The Bottom Line:
In this one small study, taking fish oil supplements appears to help late stage lung cancer patients tolerate their chemotherapy better so that they can get the most benefit from it. And, fish oil is inexpensive and has no known risks. More research is needed to find out if fish oil is usually effective for lung cancer patients and possibly other cancer patients. Since fish oil is very safe, if you or someone you know is about to start chemotherapy, it’s probably a good idea to start taking fish oil supplements right away.
 Natural Medicines Comprehensive Database. Fish oil. Fish Oil: Medline Plus supplements. 2012. Available at: http://www.nlm.nih.gov/medlineplus/druginfo/natural/993.html. Accessed February 4, 2013.
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