Here are a couple of interesting studies published on Vitamin D and Magnesium.
Vitamin D deficiency has been associated with the development of many diseases of so called aging including MS, cancer and diabetes to name a few.
Recently a new study has identified low levels of vitamin D in the abnormal development and function of the nervous system as well.
Source: Vitamin D, nervous system and aging
A recent study suggests that getting enough magnesium could help reduce the risk of developing diabetes. Magnesium supplementation was associated with a decrease in inflammation and improved insulin resistance, two risk factors related to diabetes development.