Vitamin D, the “sun” vitamin, is most commonly associated with bone health. It can be made by your body given sun exposure or taken as a supplement. Food (even fortified food sources) is generally low in vitamin D. Low levels of vitamin D have been associated with higher risk of autoimmune conditions such of as multiple sclerosis, rheumatoid arthritis, and diabetes mellitus type 1. Recent studies also point to a relationship between type 2 diabetes and low vitamin D levels.
The starkest relationship between vitamin D and diabetes is from studies in Finland, a land with long periods with very little sunlight and a population with an extremely high incidence of type 1 diabetes. In that population, supplementation with 2,000 IU of vitamin D led to an 88% reduction in the risk of type 1 diabetes. In contrast, in children who were thought to have rickets (a severe manifestation of vitamin D deficiency), the risk of type 1 diabetes was increased threefold. It is evident from these studies that Vitamin D may be helpful in preventing a number of autoimmune conditions.
Similarly, studies from Finland have shown reduced ability to handle carbohydrates in people with low levels of vitamin D. Other studies demonstrate lower insulin resistance and improved ability to secrete insulin with higher levels of vitamin D. A lower risk of type 2 diabetes has been seen with higher levels of vitamin D in many studies. Vitamin D may also help to protect the kidney as shown in studies where urinary protein loss was reduced with vitamin D supplementation. Lastly, some research has even shown better glucose control with vitamin D supplementation in type 2 diabetic patients.
Vitamin D may be especially important in pregnant women who are at risk for gestational diabetes (GDM), as some studies have shown a protective effect from vitamin D for these women. Mothers with low levels of vitamin D had a greater than 1.6-fold risk of GDM.
For those who have not had vitamin D levels checked, supplementation with 2,000 IU of vitamin D is reasonable. With monitoring, targeting a serum concentration of between 40 and 60ng/dl should be the goal. Often this will require daily dosing of between 4,000 and 10,000 IU to achieve target levels. Higher daily doses are generally necessary for those with increased body weight and darker skin. Vitamin D comes in many forms, but keep in mind that the gel or liquid forms of the vitamin are much better absorbed than tablets. Talk with your doctor if you are thinking about starting vitamin D supplementation for yourself.