Fish oil has long been touted as a supplement that improves heath and reduces inflammation, thanks to its omega-3 fatty acids. There have been many studies that seek to determine whether fish oil supplements can help prevent or combat cancer. Attention has been focused especially on breast, colon and prostate cancers. Scientific evidence does not clearly point to this benefit, however, according to the American Cancer Society.
Identification
Fish oil that comes from coldwater fish like salmon, herring and mackerel has two types of omega-3 fatty acids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). The body cannot make omega-3 fatty acids, so people must take them in via food or supplements. Other fish with omega-3 fatty acids include tuna, halibut and sardines. The amount of omega-3s commonly found in fish oil supplements is 180 mg EPA and 120 mg of DHA, reports the University of Maryland Medical Center.
Significance
Omega-3 fatty acids can reduce inflammation as well as the risk for some chronic diseases. However, it might not be a panacea for cancer, reports Brian Dakss of CBS News in his Jan. 6, 2006 story, "Fish Oil Disappoints Vs. Cancer." The National Institutes of Health gives fish oil a "C" rating as a cancer fighter. This means that scientific evidence that backs using fish oil for cancer prevention is unclear.
Theories/Speculation
Omega-3 fatty acids do show promise for preventing some cancers based on preliminary studies. For example, laboratory as well as animal studies have found that omega-3s prevent colon cancer from worsening, according to UMMC. Recommendations based on preliminary studies say that people in the early stages of the disease should take fish oil daily to slow colon cancer progression. Population-based studies also indicate that a diet that is low in fat and includes fish oil may prevent prostate cancer, according to UMMC. Fish oil also appears to help prevent breast cancer, but the definitive proof is still undetermined regarding taking fish oil for this purpose.
Expert Insight
The ACS advises that while fish oil helps prevent heart disease, fish oil supplements likely do not reduce risk for cancer. The advice is based on a reanalysis of 40 years of research, according to the society. Fish oil may improve weight loss related to cancer, but evidence of this potential benefit is mixed as well, according to ACS.
Considerations
Fish oil supplement makers are not required to prove that their products are effective or safe as long as they don't make any medical claims, ACS warns. The actual amounts of omega-3 fatty acids in different brands--or even batches of a single brand--can vary. Also, people need to speak to a doctor before supplementing with fish oil because omega-3s can have drug interactions. For example, it inhibits blood clotting, so people who take aspirin or blood-thinning medicines may have a risk of excessive bleeding if they also add fish oil, ACS warns.
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