The findings, published in Diabetes, examined the association between plasma levels of vitamin D –measured as 25-hydroxyvitamin D (25[OH]D) concentration – and islet autoimmunity(IA), which has been implicated in the development and progression of type 1 diabetes.
"For several years there has been controversy among scientists about whether vitamin D lowers the risk of developing of islet autoimmunity and type 1 diabetes," commented lead author Dr Jill Norris from the Colorado School of Public Health.
Type 1 diabetes is a chronic autoimmune disease that is now the most common metabolic disorder in children under age 10 and it increasing by between 3% and 5% annually worldwide.
While it has long been known that islet autoimmunity – which occurs when the immune system attacks the islet cells in the pancreas that produce insulin – is a precursor to type 1 diabetes, evidence for the suggestion that vitamin D levels may play a role in the development of this autoimmunity, and therefore the progression of type 1 diabetes, has been mixed.
Norris and her team reported that higher concentration of circulating 25(OH)D were linked to a decreased risk of IA in children who are at increased risk for type 1 diabetes – but noted that further studies are needed to confirm the associations, and “to enhance knowledge of how variation in vitamin D metabolism genes may alter individual responsiveness to vitamin D.
The findings are part of The Environmental Determinants of Diabetes in the Young (TEDDY) study, a large, multi-national study funded by the National Institutes of Health's National Institute of Diabetes and Digestive and Kidney Diseases.
The aim of the study is to search for triggers and protective factors for type 1 diabetes in 8,676 children with elevated type 1 diabetes risk. TEDDY children were followed with blood samples drawn every three to six months from infancy, to determine the presence of islet autoimmunity, as well as levels of vitamin D.
In the current study, Norris and colleagues compared 376 children who developed islet autoimmunity with 1,041 children who did not – finding that in children with a genetic variant in the vitamin D receptor gene, vitamin D levels in infancy and childhood were lower in those that went on to develop islet autoimmunity compared with those that did not develop autoimmunity.
It is study is the first to show that higher childhood vitamin D levels are significantly associated with a decreased risk of IA.
"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," Norris added.
Published online ahead of print, doi: 10.2337/db17-0802
“Plasma 25-Hydroxyvitamin D Concentration and Risk of Islet Autoimmunity”
Authors: Jill M. Norris, et al