January 24, 2006
Consuming food or dietary supplements such as fish oil that contain omega-3 fatty acids provides no protection against developing cancer, according to a RAND Corporation study published today in the Journal of the American Medical Association.
Assessing four decades of medical studies that examined the link between cancer and consumption of omega-3 fatty acids — the beneficial component ingested by eating fish or taking a fish oil supplement — RAND Health researchers found no link between the two.
“Omega-3 fatty acids have been shown to have beneficial health effects, particularly reducing the incidence of cardiovascular disease,” said lead author Dr. Catherine MacLean of RAND Health and the Greater Los Angeles VA Healthcare System. “We found cancer prevention isn't one of the health benefits.”
“We identified a few studies that showed reduced risk of cancer from consuming omega-3 fatty acids,” MacLean added. “But we found even more studies that showed no decrease in cancer risk and even a few that suggested a higher risk. Our conclusion is that there is no relationship between omega-3 fatty acids and lower rates of any types of cancer.”
Research on animals and a few earlier human studies have suggested that people who consume more omega-3 fatty acids may be at a lower risk of breast cancer and several other types of cancer. Based on this work, cancer-prevention has been a benefit touted by makers of some dietary supplements containing omega-3 fatty acids.
The RAND study was part of a larger project supported by the U.S. Health and Human Service's Agency for Healthcare Research and Quality and the National Institutes of Health's Office of Dietary Supplements that reviewed the scientific evidence of the health benefits of omega-3 fatty acids. Other researchers confirmed that consuming fish oil can help reduce deaths from heart disease.
MacLean and her colleagues from the RAND-based Southern California Evidence-Based Practice Center searched the medical literature for all studies exploring the relationship between omega-3 fatty acids and cancer prevention that were published between 1966 and 2005. The center is one of 13 federally sponsored evidence-based practice programs that conduct systematic reviews and technology assessments of all aspects of health care.
After closely reviewing more than 1,000 related articles, they found 38 reports that provided high-quality information about the possible link between consumption of fish oil and the incidence of 11 types of cancer. Most of the papers focused on cancers of the breast, colon, lung and prostate.
A few individual studies found that people who consumed more omega-3 fatty acids had lower risk of developing breast cancer, colon cancer, lung cancer and prostate cancer. But all of those studies involved a relatively small number of patients, according to the RAND study, which appears in the Jan. 25 edition of JAMA.
The majority of the studies examined by researchers found no association between higher consumption of omega-3 fatty acids and the lower incidence of cancer. All of the studies that included large groups of patients found that omega-3 fatty acids had no impact on the occurrence of cancer.
Other authors of the study are: Sydne Newberry, Dr. Walter Mojica, Marika Suttorp, Dr. Yee-Wei Lim, Lara Hilton and Rena Garland of RAND; Dr. Puja Khanna of Wayne State University School of Medicine; Amalia M. Issa and Shana B. Traina of the UCLA School of Public Health; and Sally Morton of RTI International.
RAND Health is the nation's largest independent health policy research program, with a broad research portfolio that focuses on health care quality, costs and delivery, among other topics.