Supplementing with vitamin D in people with low levels lowers the risk of dying from any cause by 60% according to an article in the November 7, 2011 issue of the American Journal of Cardiology looking at 10,000 people. This is a landmark study documenting that elevating low levels of vitamin D makes a profound difference in mortality.
Low levels of vitamin D are associated with twice the risk of type 2 diabetes, 40% higher risk of hypertesion, 30% increased risk of cardiomyopathy, and a three times higher risk for all cause mortality.
Replacement is usually between 2 and 5000 IU of vitamin D, but it is very important to measure the level of vitamin D to determine the dosage needed. Factors making it difficult to get sufficient vitamin D include, use of sun screen, dark skin, clothing, season, and age. UVB rays provide 90% of our vitamn D; they are needed to make vitamin D in our skin, but the rays are absent during winter, and they don't penetrate clothing, fog, smog, clouds or windows.
