Behind the Daily Mail headlines – vitamin D and type 1 diabetes

Posted on 25 October 2017

The Daily Mail reported today that “vitamin D in childhood prevents type 1 diabetes.” This interpretation of the scientific study behind the story is inaccurate, and here we explain why.

What was the study?

In type 1 diabetes, the immune system wrongly attacks and destroys the insulin-producing beta cells in the pancreas. Before the onset of type 1, the body starts to develop an autoimmune response to the islets in the pancreas, which contain the beta cells. This is known as islet autoimmunity.

The study was looking at the relationship between vitamin D levels and islet autoimmunity. The researchers were investigating whether the two were linked in children at high genetic risk of developing type 1, and whether genes related to vitamin D absorption also played a role.

This study was part of the TEDDY group studies, which JDRF funds. TEDDY – which stands for The Environmental Determinants of Diabetes in the Young – is tracking thousands of children at high risk of type 1, to see how environmental factors may affect the development of type 1.

The children have blood samples analysed regularly, so that researchers can spot trends or patterns that might suggest certain environmental factors could ‘trigger’ type 1 development.

What did the study find?

The team compared 376 children who developed islet autoimmunity – who would likely go on to develop type 1 diabetes – with 1,041 children who did not. The researchers found that higher vitamin D levels were associated with a lower risk of developing islet autoimmunity. This link was particularly true for children with a specific version of a gene that helps the body absorb vitamin D.

The researchers concluded that children who were already at risk of developing type 1 diabetes and who also had a particular version of a vitamin D absorption gene experienced a decreased risk of developing islet autoimmunity when they had higher levels of vitamin D in their bodies.

This study does not suggest that children who have low levels of vitamin D will always go on to develop type 1 diabetes, and there is no evidence that vitamin D can protect against type 1 diabetes.

What we don’t know

This study found a link between vitamin D and islet autoimmunity, but how exactly the two are linked remains unclear – it may be that one causes the other, or that both are linked by some other, unknown factor.

In their paper, the authors state that they were unable to study a link between vitamin D deficiency and the development of the autoimmune response. They also indicate that it is possible that differences in vitamin D levels may be indicative of another factor, such as different lifestyles, which may be the reason behind the difference in risk of developing islet autoimmunity.

Dr Jill Norris, the first author on the paper, emphasised that more work is needed to understand how vitamin D may be linked with type 1 diabetes:

“Since this association does not prove cause-and-effect, we look to future prospective studies to confirm whether a vitamin D intervention can help prevent type 1 diabetes.”