Omega 3 fatty acids and cardiovascular disease

Editor—Concern about depletion of fish stocks will not be addressed by supplementing animal feed with fish oil, as suggested by Din et al,¹ because this requires the harvesting of wild fish to provide the fish oil. Fish farming does not provide a solution as farmed fish contains fewer omega 3 fatty acids, this being dependent on what they are fed—usually wild caught fish products.²

Figure 1.

Marine algae: source of omega 3 fatty acids

Credit: SINCLAIR STAMMERS/SPL

The original source of the long chain omega 3 fatty acids found in fish is, however, the chloroplasts of marine algae and phytoplankton at the bottom of the food chain.³ In the marine environment polyunsaturated fatty acids may provide the degree of desaturation needed to keep cell membranes fluid in cold water. Rather than genetically modifying terrestrial plants to produce eicosapentaenoic and docosahexanoic acid, marine algae can be cultured industrially to provide the “fish” oil while leaving the fish alone.⁴

If cod liver oil is used as a source of fish oil it is important to remember that this contains a comparatively high concentration of vitamin A, producing a risk of toxicity.⁵