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The “Sun” Vitamin – Vitamin D

By Daniel Nadeau, MD

Dr. Nadeau is an accomplished physician who brings extensive experience to and the Mary & Dick Allen Diabetes Center as Program Director and Endocrinologist at Hoag Medical Group. While he has many areas of interest, the majority of his recent work, research, and lectures focus on diabetes, obesity, and nutrition.

Vitamin D is the “sun” vitamin and can be made by your body with sun exposure or taken as a supplement. It is most commonly associated with bone health. Food sources, even fortified food sources, are low in vitamin D. Low levels of vitamin D have also been associated with higher risk of autoimmune conditions such 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 type 1 studies in Finland, a land with long periods with 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 lead to an 88% reduction in risk of type 1 diabetes. In contrast, children who were thought to have rickets (severe vitamin D deficiency) showed a much higher risk of type 1 diabetes. Vitamin D may be helpful in preventing a number of autoimmune conditions.

Related to type 2 diabetes, also from Finland, studies have shown a reduced ability to handle carbohydrates with low levels of vitamin D. Other studies show 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 some but not all studies. Vitamin D may help to protect the kidney as shown in studies where urinary protein loss was reduced with vitamin D supplementation. Some studies have even shown better glucose control with vitamin D supplementation in type 2 patients.

Vitamin D may be especially important in pregnant women at risk for gestational diabetes with studies showing a protective effect of vitamin D. Mothers with low levels of vitamin D were had a greater than 1.6 fold risk of gestational diabetes.

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 60 ng/dl should be the goal. Often this will require daily dosing of between 4,000 and even up to 10,000 IU per day to achieve target levels. Requirements are generally higher with increased body weight and darker skin. Gel or liquid forms of the vitamin are better absorbed than tablets.