Norwegian scientists measured the effects of different feeds on the nutritional composition of farm-raised salmon. Fish fed a diet high in vegetable oils have a much less favorable fatty acid composition than the salmon that consume a fish-oil rich diet. They also found that heart disease patients who ate the vegetable-oil fed salmon did not show the same cardiovascular improvements as patients who ate fish-oil fed salmon.
Typically farmed Salmon are fed corn products and byproducts - high in Omega-6 vegetable oil. Wild salmon eat krill, smaller fish, and algae, all rich sources of Omega-3 fatty acids and antioxidants such as astaxanthin. It is no wonder that wild salmon are beneficial (having anti-inflammatory properties) and farmed salmon is now found to not only not be beneficial (containing higher levels of antibiotics and pesticides), but they may be pro-inflammatory.
Monica Reinagel, in her book The Inflammation-Free Diet Plan: The Scientific Way to Lose Weight, Slow Aging, Prevent Disease, and Banish Pain created the Inflammation Factor (IF) rating scale. She rates 3 oz. wild salmon +518, and 3 oz. farm raised Atlantic salmon -181, where wild salmon is the most anti-inflammatory food you can consume, and farm raised salmon rates between 1/2 cup of chocolate ice cream (-127) and a medium order of French fries (-336).
Background Cardioprotective effects of omega-3 polyunsaturated fatty acids (n-3 PUFAs) of marine origin are well recognized. Because of the shortness of marine resources vegetable oils are increasingly used in fish farming. The effects on human health of fish fed on vegetable oils are largely unknown.
Methods In a double-blinded intervention study, 60 patients with coronary heart disease (CHD) were randomly allocated to three groups consuming approximately 700 g per week for 6 weeks of differently fed Atlantic salmon: 100% fish oil (FO), 100% rapeseed oil (RO) or 50% of each (FO/RO), resulting in fillets with high, intermediate and low levels of marine n-3 PUFAs. Patient analyses before and after the intervention period included serum fatty acid profile, serum lipoproteins, and markers of vascular inflammation.
Results The serum fatty acid profiles of the patients after the intervention mirrored those of the corresponding salmon fillets and the respective salmon feeds. Significant differences between the groups were obtained, especially for the levels of total n-3 PUFAs and the n-3/n-6 fatty acid ratio, which were markedly increased in the fish oil group in contrast to the two other groups (P < 0.02 for all). Additionally, significant reductions of serum triglycerides and of vascular cell adhesion molecule-1 and interleukin-6 were obtained in patients receiving the fish oil diet when compared with the two other groups (P < 0.05 for all).
Conclusions Tailor-made Atlantic salmon fillets very high in n-3 PUFAs of marine origin seem to impose favourable biochemical changes in patients with CHD when compared with ingestion of fillets with intermediate and low levels of marine n-3 PUFAs, when replaced by rapeseed oil.
S. L. Seierstad, I. Seljeflot, O. Johansen, R. Hansen, M. Haugen, G. Rosenlund, L. Frøyland and H. Arnesen. Dietary intake of differently fed salmon; the influence on markers of human atherosclerosis, Eur J Clin Invest 2005; 35 (1): 52 –59.
Monica Reinagel, with Julius Torelli, M.D.; The Inflammation-Free Diet Plan: The Scientific Way to Lose Weight, Banish Pain, Prevent Disease, and Slow Aging. McGraw-Hill publishers, Jan 2006