Organic: Worth the Hype? Part III: Seafood
Hello friends! Welcome to the third installment of my mini-series. When it comes to fish, the playing field is a bit different. Here, we talk about "farmed" vs "wild-caught" seafood. Environmental impacts to farmed vs wild fish is well beyond the scope of this discussion today; here we will focus simply on differences in nutritional benefits and risks for consumed contaminants.
Fish farming has grown to be a large market. About half the fish eaten globally are raised in artificial fish farms. Farmed fish eat a diet which is tailored to the species' nutritional needs. In the past, farmed fish were fed fish oil and fishmeal. These ingredients are being replaced by plant proteins, minerals and vitamins, although carnivorous fish continue to be fed some fish meal in their diet. Growth hormone use is prohibited in fish farming.
There have been a number of studies analyzing the nutritional composition and contamination of farmed fish vs wild caught fish.
Wild-caught salmon and shrimp have more favorable lipid profiles (ie more anti-inflammatory omega-3 fatty acids and less of the inflammatory omega 6 fatty acids) than the farmed varieties. Wild sea bass has also been shown to have more omega 3 fatty acids and and other healthy polyunsaturated fats compared to farmed sea bass. Farmed fish and shellfish have also been shown to have higher fat contents than their wild-caught counterparts.
When we look at levels of contaminants, such as heavy metals, studies have mixed results. Farmed salmon has been shown to have higher levels of contaminants compared to wild-caught salmon, however, in another study looking at rainbow trout, there were higher levels of heavy metals in the wild-caught fish as compared to the the farmed ones.
Overall, wild fish have a better nutritional profile compared to farmed fish, although some varieties have higher risk for containing contaminants when caught wild. Sticking to consuming smaller fishes are safer for reduced toxin exposure. The large fish like tuna, king mackerel, swordfish and orange roughy can build up higher levels of mercury in their tissues. Women planning on becoming pregnant, women who are pregnant, and kids under 6 years old should avoid eating these fish completely. The rest of us should limit our consumption to no more than once a week. As they are lower on the food chain, small fish have lower levels of contaminants.
Check out some of the resources below for more information!
Want to learn more?
Fallah AA, S. Siavash Saei-Dehkordi, Amin Nematollahi, Tina Jafari. Comparative study of heavy metal and trace element accumulation in edible tissues of farmed and wild rainbow trout (Oncorhynchus mykiss) using ICP-OES technique. 2011. Microchemical Journal. 98 (2): 275-279.
Hamilton MC, Ronald A. Hites, Steven J. Schwager, Jeffery A. Foran, Barbara A. Knuth, and, and David O. Carpenter. Lipid Composition and Contaminants in Farmed and Wild Salmon. Environmental Science & Technology 2005 39 (22), 8622-8629.
HITES RA, JEFFERY A. FORAN, DAVID O. CARPENTER, M. COREEN HAMILTON, BARBARA A. KNUTH, STEVEN J. SCHWAGER Global Assessment of Organic Contaminants in Farmed Salmon SCIENCE 09 JAN 2004 : 226-229.
Hites RA, Jeffery A. Foran, Steven J. Schwager, Barbara A. Knuth, M. Coreen Hamilton, and, and David O. Carpenter. Global Assessment of Polybrominated Diphenyl Ethers in Farmed and Wild Salmon. Environmental Science & Technology 2004 38 (19), 4945-4949.
Krajnović-Ozretic M, M. Najdek, B. Ozretić. Fatty acids in liver and muscle of farmed and wild sea bass (Dicentrarchus labrax L.). 1994. Comparative Biochemistry and Physiology Part A: Physiology. 109 (3): 611-617.
Nettleton, J.A. and Exler, J. Nutrients in Wild and Farmed Fish and Shellfish. Journal of Food Science. 1992. 57: 257-260.
H. Ouraji, A. Fereidoni, M. Shayegan and S. Asil, "Comparison of Fatty Acid Composition between Farmed and Wild Indian White Shrimps, Fnneropenaeus indicus," Food and Nutrition Sciences, Vol. 2 No. 8, 2011, pp. 824-829.