Does vitamin D help protect against type 1 diabetes?

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.


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

5 Responses to Does vitamin D help protect against type 1 diabetes?

  1. Dave 14 March 2008 at 6:46 pm #

    Hi Dr. Briffa. What range of doses was used for supplementation? Thanks.

  2. Dr John Briffa 14 March 2008 at 7:37 pm #

    Most of the studies used in this meta-analysis did not report a vit D dosage. In one, the authors estimated the dose to be 10 mcg (400 IU). In another study, 50 mcg (2000 IU) was associated with a RR of type 1 diabetes of 0.22. That’s all the detail regarding dosage contained in the paper. Hope this helps.

  3. Vitally Well 15 March 2008 at 4:44 pm #

    Generally, sticking closer to nature is best. Enjoy the sunshine! It is your best source of the best form of vitamin D for your body. It is psychologically uplifting (treats SAD – Seasonal Affective Disorder). Stop putting cancer causing chemicals on your skin to block the sun – yes, most sunblocks contain carcinogenic chemicals!

  4. Christine 20 November 2009 at 11:26 pm #

    My husband has pre-diabetes/metabolic syndrome. I have encouraged him to take chromium picolinate, magnezium/calcium /zinc supplement, and have started him on Vit D 400 I.U. daily. What dosage of Vitamin D would you recommend ? Any other suggestions please?
    His G.P. has put him on Simvastatin and Amlodopine 5mg which I don’t think he should take due to side effects.
    His blood sugar average is 5.9 and his blood pressure 140/70 (even though he often forgets to take B/P tablets)


  1. Dr. Briffa: Does vitamin D help protect against type 1 diabetes? - tanTALK - 26 May 2008

    […] Briffa: Does vitamin D help protect against type 1 diabetes? Does vitamin D help protect against type 1 diabetes? Posted on 14 March 2008 I love being out in the sun. And not just because I like it, but also […]

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