The kind of fish oil you take matters. It doesn't matter if it is from WalMart, CVS or the Merc. But it does matter that your fish oil is pure, clean and has no heavy metal (Mercury, the element, not the daughter). Please look closely. Pay more for the supplement that says it's clarified, free of metals, etc.
And I'll talk about vitamin e and vitamin b next time... if that is too boring, give me a new topic!