Loading up on vitamin D is unlikely to prevent the common cold this winter, a new study from New Zealand suggests.

Despite past research suggesting the sunshine vitamin may help clear bacteria and otherwise boost immune health, those taking monthly megadoses of vitamin D got just as many colds as those who were given vitamin-free placebo pills.

"In the population we studied, we can be very confident that it has no effect on prevention or severity (of colds)," said lead author Dr. David Murdoch, from the University of Otago in Christchurch.

That population included adults who were healthy to begin with, so Murdoch and his colleagues can't say whether vitamin D may help ward off colds in kids or people who are very deficient in the vitamin.

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