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.