Your body can naturally generate Vitamin D, but only if it gets enough of the right kind of sun. For those living above a certain latitude, that daily sun is hard to come by. David McCandless explains how to get it.
Beyond just getting outside more, McCandless' Vitamin D infographic shows who in the world is missing how much Vitamin D from their lives. It matters because D vitamins have been shown to correlate strongly with mood and energy levels, along with general effects in health and cancer prevention. To get more Vitamin D going, you could get outside more, with the proper sunblock applied, or you can pick it up in dietary supplements like egg yolks, oily fish and even margarine. It's a good read, arriving at a good time for many of us in the world's northern reaches.
Vitamin D [Information is Beautiful]