These data are intriguing, but because low vitamin D levels and heart disease are both very common, and because this was not an interventional study, it is difficult to draw firm conclusions, other than more research is probably warranted.

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Kirk Garratt, director of research at Lenox Hill Hospital in New York and an interventional cardiologist who wasn't involved in the study, said patients who choose stents shouldn't think they're "making a dreadful mistake" about their care based on the new data.

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The study is observational -- meaning the researchers followed people over time -- rather than interventional (say, having some people watch TV and others read a book), which is the gold standard for research proving cause and effect.

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