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Does vitamin D help protect against type 1 diabetes?

Posted By Dr John Briffa On 14th March 2008

I love being out in the sun. And not just because I like it, but also because of the abundant evidence linking sunlight exposure with a reduced risk of conditions such as cancer and multiple sclerosis as well as improved physical and psychological functioning. And it’s free. And I like sporting a tan.

I recently wrote about warnings here in the UK about a supposed resurgence in the bone disease ‘rickets’ in children. Until this week, I was unaware that another condition that generally starts in early life that might be caused by a deficiency of vitamin D is type 1 diabetes.

Diabetes is characterised by raised levels of sugar in the bloodstream. It comes in two main forms: type 1 and type 2. About 90 per cent cases are type 2 in form. Here, there are usually normal or even raised levels of insulin in the body. The problem usually is that the insulin doesn’t work very well. As a result, blood sugar levels are not adequately controlled.

Type 1 diabetes is different in that it is caused by inadequate levels of insulin. This condition normally develops in childhood or adolescence. It is believed to be caused by a destruction of the cells in the pancreas that are responsible for making insulin. The destruction of these cells (known as the beta-cells) comes at the hands of the body’s immune system. Type 1 diabetes is sometimes regarded, therefore, as an ‘autoimmune disorder’.

What alerted me this week to the potential link between vitamin D and type 1 diabetes was a study published on-line in the Archives of Disease in Childhood. In this study, researchers pooled together (in the form of what is known as a ‘meta-analysis’) the results from 5 epidemiological studies looking at the relationship between vitamin D supplementation in infancy (up to 1 year of age) and subsequent risk of developing type 1 diabetes.

In short, what was found that vitamin D supplementation was associated with a 29 per cent reduced risk of type 1 diabetes.

Now, epidemiological studies of this nature can’t prove that vitamin D is actually protecting against type 1 diabetes (just because two things are associated, doesn’t mean one is causing the other). However, the researchers found that the relationship between vitamin D supplementation and diabetes risk was ‘dose-dependent’. In other words, generally speaking, the higher the level of vitamin D supplementation, the lower the risk of diabetes. This finding does support the idea that vitamin D has a genuine protective role.

More supporting evidence comes in the form of research which has found that individuals diagnosed with type 1 diabetes tend to have lower levels of vitamin D in their bodies compared to those who do not have this condition.

Also, type 1 diabetes risk has been noted to be higher in countries where sunlight levels are lower (sunlight drives vitamin D production in the skin).

If vitamin D does actually protect against type 1 diabetes, how does it do it?

In this study, reference is made to the fact that vitamin D receptors exist on both the beta-cells in the pancreas that make insulin, as well as some cells in the immune system. It might be that vitamin D may help to ‘normalise’ immune activity (and reduce a tendency to ‘overreact’ to the beta cells and/or helps to protect the beta-cells from damage. Evidence from animal experiments suggests vitamin D has the ability to protect against type 1 diabetes through effects on the immune system.

To know for sure if vitamin D protects against type 1 diabetes would require randomised controlled trials (i.e. trials in which children are treated with vitamin D or placebo). In the absence of these trials, though, my tendency is to take this most recent study as another piece in the ever-growing body of evidence linking vitamin D (and sunlight) with benefits for health and disease-protection in both adults and children.

References:

Zipitis CS, et al. Vitamin D Supplementation in Early Childhood and Risk of Type 1 Diabetes: a Systematic Review and Meta-analysis. Arch Dis Child. [e-pub 13 March 2008] doi:10.1136/adc.2007.128579


http://www.drbriffa.com/blog/2008/0...ype-1-diabetes/

Giving young children vitamin D supplements may reduce their risk of developing type 1 diabetes later in life, suggests new UK research.

The study, by St Mary's Hospital for Women and Children, Manchester, showed that children who were given vitamin D supplements were 29% less likely to develop diabetes than those who did not.

Type 1 diabetes is also known as insulin dependent diabetes. It is most common among children and young people under 30. It occurs because the body is unable to make insulin due to an autoimmune process. It must be treated with insulin injections.

The Manchester team reviewed five studies that looked at the effect of vitamin D supplementation. They found that children given vitamin D supplements were 29% less likely to develop diabetes type 1. Children who received higher and more regular doses had the lowest chance of developing the disease. However, the exact doses were unclear.

Previous research has found that people newly diagnosed with type 1 diabetes have low levels of vitamin D. Studies have also found that type 1 diabetes is more common in countries where there is a low exposure to sunlight, which is needed for the body to manufacture vitamin D.

"There is a marked geographic variation in incidence, with a child in Finland being about 400 times more likely than a child in Venezuela to acquire the disease,” said the authors.

Other research has linked low levels of vitamin D and sunlight to other autoimmune disorders, including multiple sclerosis and rheumatoid arthritis.

Dr Victoria King, of the charity Diabetes UK, said more research was needed before a concrete association between vitamin D supplementation and reduced risk of diabetes can be confirmed.

[ http://www.vhi.ie/news/N200308a.jsp ]