SEATTLE — A second large, prospective study by scientists at Fred Hutchinson Cancer Research Center released on Wednesday that claimed to confirm the link between high blood concentrations of omega-3 fatty acids and an increased risk of prostate cancer drew a stark industry response from supplement trade associations.
"While we encourage researchers to continue to study omega-3 fatty acids with an open mind, it is counterproductive when studying nutrition for researchers to promote their study as if it were the only piece of research that counts," Duffy MacKay, VP scientific and regulatory affairs for the Council for Responsible Nutrition, released in a statement. "In this case in particular, it is especially disingenuous for the researchers to make the kinds of assertions we’ve seen in the press, given their results are in stark contrast to previous epidemiologic studies that … in many cases showed [omega-3 consumption had] a protective effect against prostate cancer."
Published July 11 in the online edition of the Journal of the National Cancer Institute, the latest findings suggested that high concentrations of EPA, DPA and DHA — the three anti-inflammatory and metabolically related fatty acids derived from fatty fish and fish-oil supplements — are associated with a 71% increased risk of high-grade prostate cancer. The study also found a 44% increase in the risk of low-grade prostate cancer and an overall 43% increase in risk for all prostate cancers.
The same Fred Hutch scientific team reported a similar link in a 2011 study .
However, rather than marking a cause-effect link between omega-3 consumption and increased cancer incidence, the study could have been measuring a biomarker reflecting recent intake of fish or fish oil supplements in a group of high risk cancer patients that had been told to increase their EPA and DHA levels. Comparitively, the group of non-cancer patients may have not been given the same health recommendation.
The current study analyzed data and specimens collected from men who participated in the Selenium and Vitamin E Cancer Prevention Trial (SELECT), a large randomized, placebo-controlled trial to test whether selenium and vitamin E, either alone or combined, reduced prostate cancer risk. That study, which hadn't been designed to track omega-3 consumption incidentally, found no benefit from selenium intake and an increase in prostate cancers in men who took vitamin E. "The researchers [are] quick to blame dietary supplements even though there is no evidence that anybody in this study took fish oil dietary supplements," MacKay noted. "In fact, the study demonstrates no cause and effect; it can only purport to show an association between higher plasma levels of omega-3 fatty acids and those whom the researchers advise had an increased rate of prostate cancer."
The American Heart Association, the World Health Organization, the U.S. Institute of Medicine’s Food Nutrition Board and the 2010 Dietary Guidelines all have current policies advising Americans to eat more fatty fish to get the benefits of omega-3 fish oils. "It is highly unlikely this one study will change that advice," MacKay said. "For those consumers who have concerns about prostate cancer or other questions about omega-3 fatty acids, we recommend speaking with your doctor or other healthcare practitioner.”
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