Vitamin D in childhood reduces diabetes risk

Summarized by Susan Aldridge, PhD, medical journalist
April 9, 2008

Summary

A review of the evidence shows a strong role for vitamin D supplements given in childhood protecting against the development of type 1 diabetes in later life. The higher the dose, the greater the protection. Further research is needed to find out the formulation, dose and duration of supplementation that will afford most protection.

Introduction

Type 1 diabetes is an autoimmune disease in which the body destroys the insulin-producing cells in the pancreas, leaving the patient dependent upon insulin injections to control blood glucose levels. The disease is not well understood, but often starts in childhood and is most common among those of European descent, affecting around 2 million people in Europe and North America. What is more, those in Northern latitudes are more likely to be affected; a child in Finland is 400 times more likely to have type 1 diabetes than a child in Venezuela. The disease is increasing at a rate of about three percent per year and it has been predicted that by 2010 there will be 40 percent more cases of type 1 diabetes than there were in 2000. There is, therefore, an urgent need for better understanding of what causes type 1 diabetes.

Previous research has suggested that vitamin D supplementation in childhood might protect against type 1 diabetes and other autoimmune diseases like multiple sclerosis and rheumatoid arthritis. Vitamin D is obtained either from within the body, by exposure to sunlight, or from the diet. In some northern areas, children are short of vitamin D because of a lack of sunlight. There is also little vitamin D in breast milk. Therefore, vitamin D supplements have been recommended for infants but the uptake and dosage of these is variable. Researchers in Manchester, UK, have carried out a review of research on vitamin D supplementation and later development of type 1 diabetes, to determine whether this might be a useful way of helping protect children from the disease.

What was done

The researchers looked for high quality clinical trials that compared the risk of type 1 diabetes among those taking vitamin D with those who did not take it. They found five such trials, covering 6455 individuals in several European countries.

What was found

Overall, children given vitamin D supplementation had a 30 percent reduced risk of developing type 1 diabetes compared to children who did not receive supplements. There was also a dose response effect. Those who had been diagnosed with rickets, which is a sure sign of vitamin D deficiency, went on to be the most likely to develop type 1 diabetes. And those who received the most regular and higher doses of vitamin D had the lowest risk of type 1 diabetes.

What this study means

The mechanism by which vitamin D supplementation may protect against type 1 diabetes remains unclear. However, there are vitamin D receptors on both insulin-producing cells and immune cells, suggesting that the vitamin plays a role in their healthy function. The study does not prove a cause and effect relationship between vitamin D and protection against diabetes. A further long-term trial designed specifically to address this question is now needed. Further investigation is also needed into how much vitamin D is needed, and for how long, to gain maximum protection.

Source

• Zipitis CD and Akobeng AK, Vitamin D supplementation in early childhood and risk of type 1 diabetes: a systematic review and meta-analysis Archives of Disease in Childhood online 2008; doi:10.1136.adc.2007.128579

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