And if you gather enough meta-studies showing "Supplementation of x in y circumstance had no significant effect", then it starts to become reasonable to claim supplementing x in general is not worthwhile
Woah, that's a horrible way to approach things.
As far as I know vitamin C only prevents exactly one ailment, scurvy. By that token, you could test against a hundred other random conditions and claim you'd proved it was worthless. Of course, you test substances for ailments you have a reason to think they will prove effective against and any other tests are beside the point.
Also, whatever the merit of the study mentioned, for its purse, the GP citing here is kind of misleading or irrelevant. People don't take fish oil to cure their existing heart disease, they take supplements to prevent heart disease (which it may or may not do regardless of whether or not it does other things).
There is no evidence that vitamin C supplementation has any benefit. I have seen studies on this, and they don't show any benefit.
Please note the difference between supplementation and deficiency. I am using "supplementation" in the same way that I understand the medical community uses it: for strictly when you are supplementing a normal diet, and you are not already deficient in that vitamin or compound. If you are deficient in vitamin C because you are forced to eat foods without it for a long period, then you should take vitamin C pills to prevent scurvy. But if you are not deficient in vitamin C, and you do get it from your normal diet, then no one has established any benefit to its supplementation.
In that context, I think that the meta-study is relevant. People supplemented their normal diet with omega-3s, and it didn't help. Yes, there are other circumstances we have to test. We have not "proved" that omega-3 supplementation is not beneficial. But we need to amass a large corpus of evidence to address the question, and that is part of it.
Woah, that's a horrible way to approach things.
As far as I know vitamin C only prevents exactly one ailment, scurvy. By that token, you could test against a hundred other random conditions and claim you'd proved it was worthless. Of course, you test substances for ailments you have a reason to think they will prove effective against and any other tests are beside the point.
Also, whatever the merit of the study mentioned, for its purse, the GP citing here is kind of misleading or irrelevant. People don't take fish oil to cure their existing heart disease, they take supplements to prevent heart disease (which it may or may not do regardless of whether or not it does other things).