As an example, there's plenty of data looking at the benefits of fish (oil) .  Granted, most of it is observational, but hey, that's better than nothing.  In marketing parlance, fish oil is also referred to as omega 3, a name & descriptor of its polyunsaturated biochemical nature.  As it turns out, there are also omega 6's & 9's, both polyunsaturated fats, too.  And as we all know, polyunsaturated fats are better for us than saturated ones, right?  That's why product labels mention omega 3 content plus "other" omega oils.  In fact, one brand touts its "balanced blend of omega 3-6-9 fatty acids" as if that alone makes their product better than every one else's.