Page 28 of the February 2018 edition of Which? magazine says,
(You don't need...)
Fish oils such as Omega 3 capsules
Unless you are advised to take these, you don't need to. Studies show that fish oil's positive benefits are gained though eating oily fish, not supplements.
Is this true? What are these studies? Assuming eating oily fish has positive benefits, to what extent is it true that benefits are not gained through supplements (fish oil capsules)?
Is this lack of benefit equally true for diets which are already e.g. mostly-vegan, which don't need to eat fish in order to "eat less red meat etc." (or whatever other beneficial side-effects of eating fish might be)?
In case it matters I'm especially interested in "fish oils" as a source of DHA, more than omega-3.