The "sunshine vitamin " may come with a dark side. Just as a lack of vitamin D can lead to health dangers, so too can an excess. For years now, scientists have warned that not everyone needs to take vitamin D supplements, and that, in rare cases, high-dose versions can be toxic , especially for young kids and older adults. As the supplement grows in popularity, it's more important now than ever that patients and doctors are aware of the dose and the downsides. The risks might be rare, but they'