Human clinical trials have shown that fish oils reduce the risk of a variety of disorders including CVD. Despite this, results have been inconsistent. Fish oils are easily oxidised and some fish oils contain higher than recommended levels of oxidised products, but their effects have not been investigated. Recent evidence indicates that dietary oxidised fats can contribute to the development of atherosclerosis and thrombosis. This review summarises findings from cellular, animal and human trials that have examined the effects of oxidised lipids and their potential to affect health outcomes, and proposes that oxidised products in fish oils may attenuate their beneficial effects. More research is required to determine the magnitude of negative effects of fish oil on health outcomes in clinical trials.

New Zealand Greenshell mussels and hoki are caught throughout the year and oil is extracted from the processing discards. However, there is little information on the variability in the lipid profile during the annual cycle. The livers of male and female hoki (Macruronus novaezelandiae), Greenshell mussels (Perna canaliculus), blue mussels (Mytilus edulis aoteanus) and rock oysters (Saccostrea cucullata) were therefore collected four times during a 12-month period, and their lipid and lipid-soluble components were analyzed. The yield of oil obtained from hoki livers ranged from 21 ± 1 to 70 ± 2% (w/w), with a low yield occurring during their winter spawning season. Female livers generally contained a higher level of lipid than male livers. The yield of oil from whole shellfish was relatively small, ranging from 0.5 to 2% (w/w), with a higher lipid content in the summer season than in winter. Levels of omega-3 fatty acids in hoki liver oil, 18-22% (w/w) of oil, were consistent throughout the year. Omega-3 fatty acids in the three shellfish species were present at 9-20% (w/w) of oil, and showed large variations in quantity at different sampling dates. Blue mussels and rock oysters both produced lower levels of oil and omega-3 fatty acids, and showed more variability compared with Greenshell mussels.