Vitamin D may help reduce type 1 diabetes risk in susceptible children

"Vitamin D in childhood prevents type 1 diabetes: Sunshine supplement boosts the immune system of those susceptible to the condition and lowers their risk," the Mail Online reports.

In type 1 diabetes, the body produces antibodies that attack cells in the pancreas. This means the pancreas can't produce insulin, a hormone that controls blood sugar.

The condition is known to run in families, although most people with a family history will not develop it.

Researchers followed a large group of children at hereditary risk of developing type 1 diabetes and tried to see whether vitamin D levels affected their risk of developing the condition.

The study measured blood vitamin D levels during infancy and childhood, and then compared levels among those who did and did not develop antibodies.

In general, higher vitamin D levels were linked with a lower risk of producing antibodies and therefore a lower risk of developing type 1 diabetes.

However, not all children with antibodies necessarily go on to develop type 1 diabetes.

We also don't know if vitamin D would affect the risk of type 1 diabetes in the general population or if it's only in children with a hereditary risk.

There are also likely to be many other factors that influence both vitamin D levels and the development of type 1 diabetes – vitamin D is unlikely to provide the whole answer.

It's already recommended that children up to five years old take a daily vitamin D supplement. This should also be considered for older children, particularly during the autumn and winter months.

Read more advice about vitamin D supplements.

Where did the study come from?

The study was carried out by researchers from the University of Colorado, University of South Florida, and other institutions in the US, Finland, Sweden and Germany.

It was funded by the National Institute of Diabetes and Digestive and Kidney Diseases, National Institute of Allergy and Infectious Diseases, National Institute of Child Health and Human Development, National Institute of Environmental Health Sciences, Juvenile Diabetes Research Foundation, and Centers for Disease Control and Prevention.

The study was published in the peer-reviewed medical journal Diabetes.

The Mail Online is not quite correct in saying vitamin D prevents type 1 diabetes. The study didn't actually demonstrate this; it only looked at how blood vitamin D levels were linked with the development of type 1 diabetes antibodies.

What kind of research was this?

This was a cohort study following children at hereditary risk of developing type 1 diabetes and looking at whether vitamin D levels affected their risk of developing the condition.

Type 1 diabetes is an autoimmune condition (where the body's immune system attacks healthy body tissue by mistake). Although there isn't always a known cause for the autoimmune reaction, type 1 diabetes can run in families, so this research looked at children with a genetic risk.

The researchers discussed how previous studies indicated that vitamin D may have a protective effect on the immune system and that taking supplements in childhood may reduce risk.

The current study looked at the link between vitamin D concentration and immune response. It also looked at whether gene variants in how the body breaks down and then makes use of vitamin D (the vitamin D metabolic pathway) may have an influence.

What did the research involve?

The cohort included 8,676 children born in the US and Europe between 2004 and 2010 who had a hereditary risk of type 1 diabetes.

The children were enrolled in the study before four months of age and had a follow-up every three months up to the age of two, and then every six months up until May 2012.

From the full cohort, the researchers identified 418 children who had the antibodies, confirmed in two consecutive samples at two laboratories.

On average, the children were 21 months old when they developed the antibodies. Each one was matched – in terms of age, gender, family history and study centre – to three controls who hadn't developed antibodies.

The researchers looked at vitamin D concentrations prior to the identification of antibodies, or at the matched time for the control subjects. They then looked for any links between gene variants, and the way the body breaks down and makes use of the Vitamin D.

After excluding children with missing data on vitamin D levels or vitamin D genes, the researchers had a total 376 children with antibodies and 1,041 matched controls for analysis.

What were the basic results?

On average, 58% of the cohort had the recommended level of childhood vitamin D (≥50nmol/L), although only 49% had sufficient levels before the age of one.

In general, higher vitamin D levels were linked with a lower risk of developing antibodies. The risk was estimated to be around 32% lower.

The researchers also found signs that variants in vitamin D metabolism genes had an effect. A single letter variant on one metabolism gene (VDR) gave greater protection against developing antibodies if the child had sufficient vitamin D concentration.

How did the researchers interpret the results?

They said: "Vitamin D and VDR may have a combined role in [islet autoimmunity] development in children at increased genetic risk [for type 1 diabetes]."

Conclusion

This study suggests vitamin D may play some part in influencing the immune response of people with a hereditary risk of type 1 diabetes.

There are a few points to bear in mind, however:

• All children in this study had a hereditary risk of developing type 1 diabetes, with a 6% risk of developing the disease. If what this study suggests is true, then higher levels of vitamin D would reduce the risk by 30-40%, lowering it to around 4% for these children.
• At the general population level, any individual child's baseline risk of developing type 1 diabetes is smaller, at 0.5%. It isn't known if the same protective effect of vitamin D would apply to children without diabetes genes. But if it did, higher levels of vitamin D would reduce the risk only slightly, to about 0.3%.
• The study looked at the development of antibodies, but we don't know how many of the children in this study actually went on to develop clinical diabetes.
• Many other biological, health and environmental factors are likely to influence whether or not a person at hereditary risk of type 1 diabetes goes on to develop the condition, and these factors could also be confounding the link with vitamin D. For example, an active outdoor lifestyle and a varied, healthy diet could influence both vitamin D levels and diabetes risk.

It's doubtful that vitamin D provides the whole answer to the development of type 1 diabetes – having sufficient levels of vitamin D is unlikely to guarantee full protection against the disease.