Studies link low vitamin D levels and all-cause mortality.
According to the British Medical Journal, 16-year studies of US and European participants, ages 50–79, revealed a link between low vitamin D levels and cardiovascular deaths, cancer mortality (in those with a history of cancer), and all-cause mortality (the mortality rate for a population across all causes).
So how do you get the vitamin D you need? The most natural way is by exposing your bare skin to sunlight, but only for half the time it takes for you to begin burning. You can also get vitamin D by taking supplements, preferably vitamin D3.
Environmental Nutrition, October 2014, and www.vitamindcouncil.org, “How do I get the vitamin D my body needs?”