Vitamin D Linked to Type 1 Diabetes

Vitamin D Linked to Type 1 Diabetes
American Diabetes Association

What is the problem and what is known about it so far?

Type 1 diabetes runs in families, but environmental factors also play a role in its development. One of the factors that may protect children from type 1 diabetes is adequate vitamin D, which is either produced by the body in response to sunlight or obtained through foods and supplements. It has been suggested that a recent decrease in vitamin D supplementation for infants may be linked to an increase in the rate of type 1 diabetes. Experiments in mice have supported a possible protective role of vitamin D, but more needs to be learned about the possible protective effects of vitamin D in human infants.
Why did researchers do this particular study?

The researchers wanted to find out if vitamin D supplementation in infancy reduces the risk of developing type 1 diabetes in later life.
Who was studied?

This study included data from five previous studies of vitamin D supplementation and its effect on type 1 diabetes. The studies included children from throughout Europe.
How was the study done?

Researchers conducted a literature search to find previous studies that measured the effect of vitamin D supplementation on the risk of developing type 1 diabetes. They then analyzed the data from these studies to draw conclusions about their results.
What did the researchers find?

The risk of developing type 1 diabetes was significantly (29%) lower for infants who were supplemented with vitamin D compared to those who were not. There was also some evidence that higher doses of vitamin D resulted in more protection from type 1 diabetes. Finally, there was a suggestion that the timing of supplementation might also be important for subsequent development of diabetes.
What were the limitations of the study?

Some of the studies included in this analysis may have been biased in various ways. Four of the five studies relied on parents' recall of their children's supplementation, which may have been incorrect. None of those four studies accurately measured vitamin D levels in subjects, nor did they try to estimate the amount of vitamin D children may have gotten from food or sunlight versus supplements. Some of the control subjects in these studies may have had unknown diabetes. In addition, other risk factors for developing type 1 diabetes were not always taken into account. Finally, the researchers counted cod liver oil as similar to other vitamin D supplementation, but cod liver oil may have other components that protect against type 1 diabetes.
What are the implications of the study?

The limited studies available suggest that vitamin D supplementation in early childhood may offer protection against type 1 diabetes. However, this analysis was based on only five observational studies. Additional research using more carefully designed, larger, longer studies will be needed to confirm these findings and to learn more details about how best to supplement infants with vitamin D.