Higher Intakes of Long-Chain Omega-3 Fatty Acids and Reduced Incidence of Liver Cancer
Sawada, N. et al., Gastroenterology, in press, 2012
Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo, Japan
Hepatocellular cancer (adult primary liver cancer) has been associated with various lifestyle and other factors and exhibits a poor five-year survival rate. The present study from Japan investigated the potential relationship of omega-3 fatty acid intakes in 90,296 participants (ages 45-74 years at the beginning) and the risk of developing liver cancer. The participants completed questionnaires on various lifestyle factors including diet and their intakes of various fish/seafood. The calculated daily intakes of the short-chain omega-3 fatty acid (ALA : alpha-linolenic acid) and the long-chain omega-3 fatty acids found mainly in fish/seafood (EPA : eicosapentaenoic acid , DPA: docosapentaenoic acid, DHA : docosahexaenoic acid) were determined from food frequency intakes and their omega-3 fatty acid contents in the foods.
A significant inverse relationship was found between the intake of fish enriched in long-chain omega-3 fatty acids and the risk of liver cancer such that those in the top quintile (top 20 %) with respect to consumption exhibited a 25 % lower risk as compared to those in the lowest quintile . When adjusting for various other confounding factors (multivariate analyses), no relationship of ALA intakes to liver cancer risk was found. In contrast, significant inverse relationships between increasing intakes of the long-chain omega-3 fatty acids and liver cancer were found. Those in the highest quintiles with respect to intakes of EPA, DPA, and DHA exhibited lowered risks of liver cancer by 44 %, 36 %, and 29 %, respectively, as compared to those in the lowest quintiles of intakes.
The authors indicate that their results may lead to important implications for public health and suggest that a greater consumption of omega-3 fish and omega-3 fatty acids may modify the development of hepatocellular carcinoma among those subjects infected with hepatitis B or hepatitis C virus.
Dr. Holub's Comments:
The median intakes of EPA and DHA for the population sectors with the lowest overall risk of liver cancer were 740 mg/day and 1190 mg/day, respectively, for a summed intake of (EPA plus DHA) of 740 plus 1190 equal to 1930 mg/person/day. Such intakes are approximately 15-times greater than North American intakes (approaching 120-150 mg/person/day). Interestingly, the sector in the Japanese population with the lowest median intakes of EPA/DHA (bottom 20 %) and the highest incidence of liver cancer had summed (EPA + DHA) intakes of 420 mg/person/day which is well above North American intakes. Thus, the so-called ‘ideal’ intakes of EPA/DHA and possibly also DPA for lowering the risk of developing liver cancer in the population is worthy of future investigation.