Scientific review published in Advances in Nutrition finds, despite mounting studies, there isn’t enough strong evidence

Consumers have been urged to increase their consumption of omega-3 fatty acids, with the promise of improved health outcomes.  In particular, the results of many studies have suggested that omega-3 fatty acid intake may reduce your risk of many types of cancer.  Despite these findings, the relationship between omega-3 fatty acid consumption and cancer remains controversial and unsettled.

Published in Advances in Nutrition, the international review journal of the American Society for Nutrition, “Consumption of Fish and ω-3 Fatty Acids and Cancer Risk: An Umbrella Review of Meta-Analyses of Observational Studies” sheds new light on the controversy.  According to the authors of this scientific review, “in studies of different types of cancer included in previously published meta-analyses, differences in types and doses of omega-3 fatty acids have affected the conclusions obtained and led to contradictory and inconsistent meta-analysis findings.  A systematic approach to providing evidence is thus needed.”

“Given the shortcomings of previous studies,” the authors set out “to provide an overview and evaluate the validity of reported associations of omega-3 fatty acids with various cancer risks by the first umbrella review of the evidence across existing systematic reviews and meta-analyses of observational studies.”  Specifically, the authors evaluated the evidence by analyzing the results of 57 meta-analyses to determine whether there is an association between omega-3 fatty acid intake and cancer outcomes and, moreover, to determine how strong that association is.  These meta-analyses, in turn, examined data from individual studies of the relationship between omega-3 fatty acids and cancer in order to identify any overarching trends.

Surprisingly, the authors found that “although omega-3 fatty acids are commonly used as dietary supplements and many studies on omega-3 fatty acids have been published, there was no convincing evidence related to the effects of omega-3 fatty acids on cancer risk.”  The authors did, however, point to some weak evidence supporting the association between omega-3 fatty acids and a lower risk of breast cancer, liver cancer, prostate cancer, and brain tumor.  The authors believe that “one of the possible reasons why there is only weak evidence for effects of omega-3 fatty acids on overall organ-specific cancer risk is the combining of biologically heterogeneous cancer subtypes into one entity, which has been done in a vast majority of epidemiological studies.”

In order to determine whether or not omega-3 fatty acids prevent cancer with a high level of confidence, the authors have called for further studies “to identify the actual effects of omega-3 fatty acids on cancer risks by using individual patient data meta-analyses.”

Reference Keum Hwa Lee, Hyo Jin Seong, Gaeun Kim, Gwang Hun Jeong, Jong Yeob Kim, Hyunbong Park, Eunyoung Jung, Andreas Kronbichler, Michael Eisenhut, Brendon Stubbs, Marco Solmi, Ai Koyanagi, Sung Hwi Hong, Elena Dragioti, Leandro Fórnias Machado de Rezende, Louis Jacob, NaNa Keum, Hans J van der Vliet, Eunyoung Cho, Nicola Veronese, Giuseppe Grosso, Shuji Ogino, Mingyang Song, Joaquim Radua, Sun Jae Jung, Trevor Thompson, Sarah E Jackson, Lee Smith, Lin Yang, Hans Oh, Eun Kyoung Choi, Jae Il Shin, Edward L Giovannucci, Gabriele Gamerith, Consumption of Fish and ω-3 Fatty Acids and Cancer Risk: An Umbrella Review of Meta-Analyses of Observational Studies, Advances in Nutrition, nmaa055,

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