Fish Intake and Chronic Disease Risk
Virtanen et al., Am. J. Clin. Nutr. 88 : 1618-1625, 2008
Departments of Nutrition and Epidemiology (EBR), Harvard School of Public Health, Boston MA
The present study was derived from the Health Professionals Follow-Up Study (HPFUS), wherein 40, 230 US male health professionals aged 40-75 years and free of major chronic disease at baseline in 1986 were followed during a period of 18 years. Lifestyle and other risk factors were assessed every two years and dietary consumptions were monitored by a semi-quantitative food-frequency questionnaire (FFQ) which was conducted every four years. This provided an estimation of fish/seafood intakes; as well, nutrient intake estimates were determined based on the US Department of Agriculture and Harvard University food-composition database sources. Major chronic disease events were monitored including cardiovascular disease events, cancers, and deaths from other causes.
The men were assigned to one of five groups based on their fish consumption (servings) as follows: <1/month, 1-3/month, 1/week, 2-4/week, ≥5/week. The average intakes of the long-chain omega-3 fatty acids as EPA + DHA across these five groupings were estimated to be approximately 0.04, 0.09, 0.24, 0.45, and 0.85 g/day, respectively. By fully adjusting for multiple variables, fish consumptions of one serving/week and 2-4 servings/week were associated with a lower risk of cardiovascular disease by 14 and 15%, respectively, as compared with a fish intake of <1 serving/month. The authors found no significant associations between fish consumption and the incidence of total cancer. No statistically significant associations were found with regard to the consumption of fish and EPA + DHA and the overall incidence of major chronic disease in generally healthy men. Furthermore, no evidence was found that a high intake of omega-6 fatty acids modified the observed relationships.
Dr. Holub's Comments:
Previous studies have reported significant inverse relationships between the consumption of fish as well as EPA + DHA and mortality from sudden cardiac death whereas the present investigation found a significant inverse relationship for the former (intake) but not the latter (EPA + DHA intakes) and total cardiovascular disease. However, the present study did not evaluate the potential effects of fish intakes or (EPA + DHA) intakes on other parameters including atrial fibrillation which would better relate to sudden cardiac death and fatal ischemic heart disease or arrhythmic death. It is interesting to note that high dietary intakes of omega-6 fatty acids have often been suggested to reduce the health benefits of omega-3 fatty acids from fish. Despite high dietary intakes of omega-6 fatty acids (namely as linoleic acid) providing an average intake of approximately 12 grams/day in the population studied, statistical analysis reported no support that omega-6 consumption levels (low vs. middle vs. high) had any influence on the relationships between fish intakes and the relative risk of major chronic disease, total cardiovascular disease, and total cancer. These and other findings from population studies including the work of Mozaffarian et al. (Circulation, 111:157-164 (2005)) suggest that the widespread implication of higher intakes of omega-6 fatty acids including higher omega-6:omega-3 ratios in the diet as major health hazards deserves extensive reassessment, further evaluation, and evidence-based consensus consolidation with respect to various health-related endpoints.