BBC News, reporting on the results of a study of Vitamin D supplements, inserted a curious sentence: "The study, carried out in New Zealand, which gets more sunshine annually than the UK, found the vitamin D supplements increased blood levels of the vitamin. But this had no significant impact on the rate or severity of colds." (my italics)
This is yet another study that shows supplements/drugs that succeed in making some metric look better but fail to deliver any true health benefits.
The New Zealand sun is the alibi used by advocates of Vitamin D supplements to discredit this randomized trial. They argue that because the sun delivers Vitamin D, someone who lives under the sun would be less likely to be deficient in Vitamin D. And the supplements only help those who are deficient.
Unfortuately, this elaborate story has no collaborative evidence. Instead, we have an expert who said this is so ("a leading UK cold expert said vitamin D is useful"), bringing his own anecdote ("He said he takes [vitamin D supplement] every year as a precaution").
Test result from randomized controlled experiment versus expert opinion based on anecdotes. That's not a fair match, and yet the BBC seems to prefer the latter, and thus serves us the NZ Sun alibi.