A clear association has been shown between consumption of omega 3 oils and a reduced prevalence of cardiovascular disease. As a result, dietary addition of oily fish or omega 3 oils is recommended. Omega 3 is often taken in highly purified form as capsules as this is more presentable and convenient, and helps remove environmental contaminants such as mercury and PCBs..
While the Inuit diet was highly cardio-protective and consuming oily fish within an Western diet is to a lesser degree, the case for purified fish oil supplements is less convincing. Purification of fish oil removes lipophilic polyphenols (in particular phlorotannins) which likely contribute to the health benefits of oily fish; leaving the omega 3 highly unsaturated fatty acids exposed and prone to conferring oxidative and inflammatory stress. There is also evidence that polyphenols in olive oil also play a part in the health-promoting benefits of the Mediterranean diet. Phlorotannins may also play a protective role against cancer and Alzheimer's disease, but there is also evidence that they exert anti-nutrient effects at high doses. The authors recommend that it may be inadvisable to use purified omega 3 highly unsaturated fatty acid supplements unless appropriate co-factors are added (Clayton and Ladi, 2015).
CLAYTON PR, LADI S. From alga to omega; have we reached peak (fish) oil? JRSM 2015; 108(9):351-357.