(RxWiki News) Omega-3 fatty acids found in fatty fish and fish oil supplements have been praised for their health benefits. Now, these benefits are being called into question.
Researchers have confirmed earlier study findings that showed a link between high blood levels of omega-3 fatty acids and an increased risk of prostate cancer.
The high blood levels of the fatty acids were also found to increase the risk of high-grade prostate cancer by 71 percent.
"Talk to your doctor about all the supplements you take."
A team of researchers at the Fred Hutchinson Cancer Research Center in Seattle, Washington conducted this study, which confirmed findings from an earlier study that reached the same conclusions.
Alan Kristal, DrPH, of the Fred Hutchinson Public Health Sciences Division, was the lead author of this study.
Integrative oncologist Brian D. Lawenda, MD, told dailyRx News, "The results of this intriguing study are a shot across the bow of one of the more commonly held dietary beliefs that omega-3 fats are cancer protective, whereas omega-6 fats promote cancer.
"We have been taught that the potential anti-cancer effects of omega-3 fats are due to their anti-inflammatory nature, so this report and others that show similar findings clearly make this argument less certain," said Dr. Lawenda, who is the clinical director of Radiation Oncology at 21st Century Oncology in Las Vegas. He is also the founder of www.IntegrativeOncology-Essentials.com.
The current study analyzed data and tissue samples from men who took part in the Selenium and Vitamin E Cancer Prevention Trial (SELECT).
That trial looked to see if taking selenium and vitamin E, either alone or in combination, reduced prostate cancer risks. The trial found that vitamin E may actually increase prostate cancer risks.
A total of 834 prostate cancer patients and a comparison group of 1,393 men without prostate cancer were involved in the current study.
The researchers measured blood concentrations of EPA, DPA and DHA omega-3 fatty acids that have anti-inflammatory properties and which are found in fatty fish and fish oil supplements.
Men with high levels of these fatty acids were found to have a 44 percent increased risk of low-grade prostate cancer, and an overall 43 percent increased risk for all prostate cancers.
A 2011 study by the same scientists found the same link between high levels of DHA and more than a two times higher risk of developing high-grade prostate cancer.
"We’ve shown once again that use of nutritional supplements may be harmful," Dr. Kristal said in a prepared statement.
The reason for the association between omega-3s and prostate cancer risks is unclear. The authors said their findings don’t address the influence of the fatty acids on prostate cancer prognosis.
Dr. Lawenda said he’d like to see what role, if any, toxins found in fish may play.
"Could these results simply be confounded by higher consumption of toxin-loaded fish leading to an increased risk of prostate cancer rather than an effect of the omega-3's on cancer development? [That's] food for thought," he said.
Dr. Lawenda, who was not involved in this study, added, "This study brings up many questions, but it is important to not jump immediately to the conclusion that omega-3 fats from fish are bad.
"Population studies of cultures that consume fish as a regular part of their diet (i.e., Japan) have clearly demonstrated that they have a significantly lower risk of developing numerous cancers, including prostate cancer, compared with those who consume much less fish (i.e., Standard American Diet)," Dr. Lawenda said.
Results from this study were published July 11 in the Journal of the National Cancer Institute.
The National Cancer Institute and the National Center for Complementary and Alternative Medicine funded the research.
No conflicts of interest were reported.