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Children play soccer in the small town of Baker Lake, Nunavut in 2009. Research among children with arthritis globally shows that those residing in northern latitudes have abnormally low vitamin D levels. (Photo: THE CANADIAN PRESS/Nathan Denette)

Children with arthritis lack vitamin D

A new study points to a clear link between childhood arthritis and abnormally low levels of vitamin D, especially in northern countries.

In an analysis of global research, we recently found that children with the most frequent type of arthritis, juvenile idiopathic arthritis (JIA), have abnormally low vitamin D blood levels. We also found that those living in northern countries, such as Canada and northern European regions, are more likely to have low vitamin D levels and associated active disease.

In Canada, arthritis is among the most common chronic diseases of childhood. An estimated three in 1,000 Canadian children (more than 20,000 in total) have arthritis. The prevalence of childhood arthritis varies throughout the world.

Geographical differences in the frequency of childhood arthritis might relate to genetic, ethnic, environmental and lifestyle influences. The cause of arthritis in children is unknown, but the interaction of genetic and environmental factors is believed to be important.

Vitamin D is vital for bone health and is essential for regulating the body’s immune and inflammatory functions. The body’s level of vitamin D is also influenced by genetic factors, skin tone and clothing that affect the skin’s exposure to sunlight, and dietary intake of vitamin D.

Environmental variations in exposure to ultraviolet B radiation (UVB) from sunlight, which is necessary for activating vitamin D in the body, is affected by the latitude and season.

Kids in northern countries fare worst

Our team reviewed 38 studies from around the world. We found that in 84 per cent of them, vitamin D levels in children with JIA were lower than recommended.

Vitamin D status also followed a north-south geographical gradient — with those residing in northern latitudes having abnormally low vitamin D levels.

The analysis also showed a correlation between vitamin D status and arthritis activity as those children with lower vitamin D levels had more active arthritis.

Read more at The Conversation.

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