Confounding (Score 3, Insightful)

The article acknowledges its own shortcomings: Vitamin D levels could possibly be used as a measurement of sunlight exposure in people not taking supplements and not conscientiously eating the proper foods. So when someone's chronically ill or massively overweight and doesn't go outside to exercise, their vitamin D levels will be decreased. Those people already have an increased 8 year mortality regardless of how much vitamin D they consume or have in their diet. It's like the studies "linking" coffee to lung cancer years ago: once it was realized that lots of people smoke when they drink coffee, those studies looked ridiculous. http://en.wikipedia.org/wiki/Confounding_variable