Omega3 PUFA in Fish and Shellfish

The PUFA of many fish lipids are dominated by two members of the omega-3 («-3) family, C20:5 n-3 (EPA) and C22:6 n-3 (DHA). They are so named because the first of several double bonds occurs three carbon atoms away from the terminal end of the carbon chain.

All fish and shellfish contain some omega-3, but the amount can vary, as their relative concentrations are species specific (Table 2). Generally, the fattier fishes contain more omega-3 fatty acids than the leaner fishes. The amount of omega-3 fatty acids in farmraised products can also vary greatly, depending on the diet of the fishes or shellfish. Many companies now recognize this fact and provide a source of omega-3 fatty acids in their fish diets. Omega-3 fatty acids can be destroyed by heat, air, and light, so the less processing, heat, air exposure, and storage time the better for preserving omega-3 in fish. Freezing and normal cooking cause minimal omega-3 losses, whereas deep frying and conditions leading to oxidation (rancidity) can destroy some omega-3 fatty acids.

The beneficial effects of eating fish for human health have been well documented. Research has shown that EPA and DHA are beneficial in protecting against cardiovascular and other diseases (Table 3). Studies examining the effects of fish consumption on serum lipids indicate a reduction in triacylglycerol and VLDL-cholesterol levels, a factor that may be protective for some individuals. Research also indicates that EPA in particular reduces platelet aggregation, which may help vessels injured by plaque formation. Fish oils also appear to help stabilize the heart rhythm, a factor that may be important in people recovering from heart attacks.

Table 2 Selected fish and shellfish grouped by their omega-3 fatty-acid content

Low-level group

Medium-level group

High-level group

(<0.5g per 100g)

(0.5-1 g per 100 g)

(>1g per 100g)

Finfish

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