Omega 3 fatty acids and cardiovascular disease--fishing for a natural treatment

Abstract

Omega 3 fatty acids from fish and fish oils can protect against coronary heart disease. This article reviews the evidence regarding fish oils and coronary disease and outlines the mechanisms through which fish oils might confer cardiac benefits

Fig 1

Greenland Inuit gutting a seal in the early 1900s. Their diet consisted largely of fish, whale, seal, and walrus, resulting in a high intake of omega 3 fatty acids. Copyright Arctic Institute, used with permission from Leif Vanggaard, Arctic Institute

Fig 2

Fatty acids are saturated, monounsaturated, or polyunsaturated. Two types of polyunsaturated fatty acid exist—the omega 6 and the omega 3 fatty acids. The omega 6 fatty acids are available mainly from vegetable oils. Three types of omega 3 fatty acid exist: α linolenic acid is available from certain plants but eicosapentanoic acid and docosahexanoic acid must be obtained from marine sources

Fig 3

Structures of the two classes of polyunsaturated fatty acids. The omega 3 fatty acids have their first double bond at the third carbon molecule from the methyl (CH₃) end of the fatty acid, whereas the omega 6 fatty acids have their first double bond at the sixth carbon molecule. The chemical names for each fatty acid are also given: the number of carbon atoms is given first, followed by the number of double bonds and the position of the first double bond. Omega 6 linoleic acid can be desaturated in certain plants to form omega 3 α linolenic acid. Whereas linoleic acid is mainly converted into arachidonic acid, α linolenic is elongated and desaturated into eicosapentanoic acid and then docosahexanoic acid

Fig 4

Synthesis of eicosanoids from omega 6 and omega 3 fatty acids. Arachidonic acid and eicosapentanoic acid compete for the cyclo-oxygenase and lipoxygenase enzymes for conversion into eicosanoids. Those derived from arachidonic acid are pro-inflammatory and pro-aggregatory, whereas those derived from omega 3 fatty acids are anti-inflammatory and inhibit platelet aggregation