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Response to "Thoughts on Fatty Fish Consumption"
- Emily B. Levitan (24 August 2009)
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Thoughts on Fatty Fish Consumption
- Richard S. Harman (24 August 2009)
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Emily B. Levitan, Research Fellow Beth Israel Deaconess Medical Center, Boston, MA 02215
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I appreciate Dr. Harman’s interest(1) in the study(2) regarding fatty fish consumption, marine omega-3 fatty acids, and incidence of heart failure hospitalization and mortality. He raises several interesting points regarding fish consumption and how to evaluate its effects. He points out that cardiovascular disease develops over a lifetime and the early stages can be detected even in young, apparently healthy men. I agree that a life-course approach to studying the relationship between intake of fish and cardiovascular disease would be an important addition to the literature and would help to disentangle short-term and long-term effects. Individuals’ dietary patterns are correlated over time,(3) so current intake will, in part, reflect past intake. Dr. Harman’s suggestion for a cross-cultural study comparing the population-wide consumption of fish and the incidence of cardiovascular disease is welcome. However, this type of ecological study focused on the comparisons between groups must be interpreted with caution. First, the average population-level consumption of fish is likely to be related to many other factors that could influence cardiovascular disease, including wealth, standards of care, and other dietary factors. Second, the population-level correlation between a food of interest and rates of disease does not necessarily represent the biologic effect on an individual, a problem known as the ecologic fallacy. I agree with Dr. Harman that what people do not eat can be as important, or more important, than what they do eat. In this study population from central Sweden, fatty fish is not replacing red and processed meats. In fact, men who consumed the least fatty fish ate an average of 1.1 servings of red or processed meat per day while those who consumed the most fatty fish ate an average of 1.9 servings of red or processed meat per day. I think that previous experimental and observational research on the effects of fatty fish and marine omega-3 fatty acids support the idea that these factors may have direct effects on cardiovascular health. I am most familiar with dietary patterns in Western Europe and North America and can not comment on fish or red meat consumption in Asia. Finally, I support Dr. Harman’s position that research on diet and dietary supplements should received public funds and should be publicly accessible. This study was funded by the Swedish Research Council/Committee for infrastructure, the Swedish Foundation for International Cooperation in Research and Higher Education, and the National Heart, Lung, and Blood Institute, part of the Unites States National Institutes of Health. In accordance with US law and National Institutes of Health policy,(4) the article will be publicly accessible 1 year after publication. References 1. Harman RS. Thoughts on Fatty Fish Consumption. Eur Heart J 2009. 2. Levitan EB, Wolk A, Mittleman MA. Fish consumption, marine omega-3 fatty acids, and incidence of heart failure: a population-based prospective study of middle-aged and elderly men. Eur Heart J 2009;30(12):1495-1500. 3. Newby PK, Weismayer C, Akesson A, Tucker KL, Wolk A. Long-term stability of food patterns identified by use of factor analysis among Swedish women. J Nutr 2006; 136(3):626-633. 4. U.S. Department of Health & Human Services. National Institutes of Health Public Access. http://publicaccess.nih.gov/ (Accessed Aug 13, 2009). Conflict of Interest:None declared |
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Richard S. Harman, retired retired 23464
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(1) My uneducated guess would be that most Swedish men eat a lot of fish all their lives. If Swedish boys and young men eat a lot of fish while growing up, what they eat between ages 45 and 79 might not matter much unless there is some "latter stage" dietary benefit that kicks in after the fundamental circulatory conditions have already been developed during the first 45 years. Autopsies of US soldiers killed in Viet Nam indicated that a disappointing percentage of American young men had already developed clogged arteries by age 18. Therefore, in trying to determine if there are heart benefits that come with eating fatty fish, it might be interesting to rank all regions by fatty fish consumed from birth, then compare Swedish male heart health with all the other dietary populations of the world. If all global diets are compared to Swedish, the benefits of a fatty fish diet might be much more apparent than would appear from an internal Swedish study, assuming that the normal Swedish diet all along has included a lot of fatty fish from cold northern water. (2) A major benefit of eating a lot of fatty fish might be the substitute value of what is NOT eaten instead. This benefit should be most apparent in dietary regions where a lot of something harmful would otherwise be eaten. Beef comes to mind. Red meat, and beef in particular, is probably the largest source of absorbed iron in the human diet. Where much beef is eaten, as in the US, heart disease is probably most prevalent. In India, where beef are given religious protection so that their milk is more available than their hamburger, heart disease is at the bottom rank if not the lowest in the world. Could beef be the reason? Many Viet Namese love pho'. I wonder how significant beef is in their diet overall and if eating a lot of beef correlates with heart problems there. I do not know how much beef is normally eaten in Sweden by any of the age groups, but it would be interesting to follow two control groups of any population in the world--the first group from birth would eat a lot of fatty fish and little or no beef, the second group from birth would eat a lot of beef and little or no fatty fish. (3) "For Profit" industries seldom bother to study foods and dietary herbs or supplements because they cannot patent them and therefore see not profit in it. Apparently suffering, death, and unhappiness do not bother them enough to affect their calculations of the bottom line. I would be happier if studies of this kind would be sponsored by the people and made freely available to everyone. Nutritional guidelines and comparative benefits of different diets are of global public significance and directly affect the well-being and happiness of the world. These are much too important to be left to the whimsies of private enterprise. Conflict of Interest:None declared |
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