Why Should We Eat More Salmon?

Why Should We Eat More Salmon?

Platelets are elements in the blood that initiate blood clotting and tissue repair by releasing clotting factors and platelet-derived growth factor (PDGF). Turbulence in the bloodstream may cause platelets to rupture. Fat deposits and bifurcations of arteries lead to such turbulence, so platelets and PDGF are implicated in blood clotting and growth of atherosclerotic plaque. Furthermore, the anaerobic conditions that exist under a large plaque deposit may lead to weakness and dead cells in the arterial wall, aggravating the problem.

In cultures that depend on fish as a major food source, includ-ing some Eskimo tribes, very little heart disease is diagnosed, even though people in these groups eat high-fat diets and have high levels of blood cholesterol. Analysis of the their diet led to the discovery that certain highly unsaturated fatty acids are found in the oils of fish and diving mammals. One class of these fatty acids is called omega-3 (v₃), an example of which is eicosapentenoic acid (EPA).

CH₃CH₂(CH=CHCH₂)₅(CH₂)₂COOH

Eicosapentenoic acid (EPA)

Note the presence of a double bond at the third carbon atom from the end of the hydrocarbon tail. The omega system of nomenclature is based on numbering the double bonds from the last carbon in the fatty acid instead of the carbonyl group [the delta (D) system]. Omega is the last letter in the Greek alphabet.

The omega-3 fatty acids inhibit the formation of certain prostaglandins and thromboxane A, which is similar in structure to prostaglandins. Thromboxane released by ruptured arteries causes other platelets to clump in the immediate area and to increase the size of the blood clot. Any disruption in thrombox-ane synthesis results in a lower tendency to form blood clots and, thus, in a lower potential for artery damage.

Aspirin also inhibits prostaglandin synthesis, although it is less potent than EPA. Aspirin inhibits the synthesis of the pros-taglandins responsible for inflammation and the perception of pain. Aspirin has been implicated in reducing the incidence of heart disease, probably by a mechanism similar to that of EPA. However, people who are being treated with blood thinners or who are prone to easy bleeding should not take aspirin.