Vitamin D in childhood may help prevent type 1 diabetes
Publication Date:13/03/2008
Giving children vitamin D supplements at an early age is linked to a lower risk of type 1 diabetes in later life, a new review says. However, the research is still at a fairly early stage, and better-quality studies need to be done before doctors can be certain.
What do we know already?
If you have diabetes, your body can't control the amount of sugar in your blood on its own. It can be controlled, but it's a condition that needs careful, lifelong treatment.
There are more than 2 million people in the UK with diabetes. Of these, about 250,000 have type 1. Type 1 diabetes usually affects people when they're under 30, most commonly as teenagers.
Your risk of type 1 diabetes is partly a result of your genes. But the environment you grow up in also seems to play a part. For example, type 1 diabetes is much more common in northern countries that don't get as much sun.
Sunlight helps our bodies make vitamin D. So researchers have wondered whether a lack of vitamin D plays a part in causing type 1 diabetes. Researchers have now gone through all the studies that have been done so far, to find out whether taking vitamin D supplements as a child could reduce the risk of type 1 diabetes.
What does the new study say?
Children who took supplements of vitamin D were about a third less likely to develop type 1 diabetes as they got older. Taking supplements regularly, or taking higher doses, were linked to an even lower risk of diabetes.
Not all the studies gave detailed information on the children's ages when they look supplements. One study suggested that supplements given between 7 months and 12 months of age had the biggest effect.
Where does the study come from?
The review was done by two researchers, based at Stockport NHS Foundation Trust and Booth Hall Children's Hospital in Manchester.
How reliable are the findings?
Researchers looked through all the studies they could find on vitamin D and diabetes, and combined the results. This gives us the best picture yet of a possible link between vitamin D and a reduced risk of diabetes. But there are problems with the original studies that mean we can't be completely sure of the results.
For example, some studies looked at whether children were given vitamin D supplements, but not necessarily at other sources of vitamin D, such as sunlight or diet. So, although some children were taking vitamin supplements, other children might have been getting just as much from sunlight, foods or fortified formula milk.
Some of the studies looked at children who took cod liver oil. Cod liver oil contains vitamin D, so the researchers counted it as a vitamin D supplement. But fish oils also contain vitamin A and omega-3 fatty acids. It might have been these having an effect, not the vitamin D.
In all of the studies, parents were asked whether their children had taken vitamin D supplements. If some parents forgot, this would affect the results. Also, there may be lots of other differences between children who were given supplements and children who weren't. For example, mothers who'd breastfed might have been more careful to give their children supplements (there's not always much vitamin D in breast milk, so nursing mothers are often advised to take vitamin D supplements or give them to their children). These other differences could explain the change in diabetes risk, rather than the vitamin D.
What does this mean for me?
The study suggests that there's possibly some kind of link between regular intake of vitamin D and a reduced risk of type 1 diabetes. But the research is still in the fairly early stages. The researchers say that we need high-quality studies lasting a long time to tell us for certain whether vitamin D really helps to prevent diabetes.
What should I do now?
You probably don't need to do anything. On the basis of this study, doctors are unlikely to start recommending vitamin D to prevent diabetes. However, vitamin D supplements are already recommended for pregnant or breastfeeding women, and for young children, mainly to prevent rickets, a childhood disease that causes soft bones.
According to the Food Standards Agency, Britain's food safety watchdog, most other people are able to get enough vitamin D from sunlight and from their diet. Eggs and oily fish are two good food sources of vitamin D.
But supplements are important for people from Asian, African, Afro-Caribbean or Middle Eastern backgrounds. Having darker skin makes it harder to get enough vitamin D from sunlight. Supplements can also be useful for people who spend a lot of time indoors, or usually wear clothes that cover most of their skin. Elderly people can also benefit from supplements.
The recommended dose for vitamin D supplements is 10 micrograms (0.01 milligrams) each day for adults, with slightly lower doses recommended for children. If you're planning to give vitamin D to your child, make sure you choose a product that has a suitable dose for children.
Being in the sun helps people get enough vitamin D, but too much sun can burn and increase the risk of skin cancer. There are no official guidelines about how much sun you need to get enough vitamin D, but it's best to avoid burning and stay out of the sun when it's at its hottest.
If you're in any doubt about whether particular vitamins are right for your child, ask your GP, health visitor or pharmacist.
From:
Zipitis CS, 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. (published online 13 March 2008)
To read more, see our information on type 1 diabetes.
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