Obese children with low levels of vitamin D may be at higher risks of developing risk factors associated with diabetes such as insulin resistance, according to new research.
The study of obese and non-obese children in the USA found that low vitamin D levels were significantly more prevalent in obese children -- and were associated with risk factors for type 2 diabetes, including insulin resistance.
Researchers have reported that infants who receive the recommended daily dose of vitamin D may have a lower risk of developing type 1 diabetes. Babies who received at least 2,000 international units (IU) of vitamin D daily were nearly 80% less likely to develop type 1 diabetes over the next three decades compared with infants who had lower intakes of the vitamin, according to findings published in the The Lancet.
The advice to keep babies out of the sun, and the increase in use of sunscreen when infants and toddlers are in the sun may act together to decrease the intake and synthesis of the sunshine vitamin.
"Our study found that obese children with lower vitamin D levels had higher degrees of insulin resistance," said Dr Micah Olson of The University of Texas Southwestern Medical Center -- the lead author of the study.
"Although our study cannot prove causation, it does suggest that low vitamin D levels may play a role in the development of type 2 diabetes," he added.
Writing in the Journal of Clinical Endocrinology & Metabolism, Olson and his team reported that lower levels of blood plasma 25-hydroxyvitamin D -- 25(OH)D -- in obese children were associated with reductions in models of insulin resistance including two hour glucose tolerance tests.
High rates of vitamin D deficiency have been found in obese populations and past studies have linked low vitamin D levels to cardiovascular disease and type 2 diabetes.
However, the authors noted that the mechanisms by which obesity and its related illnesses are related to vitamin D deficiency are not fully known.
The new study examined associations between vitamin D levels and dietary habits in obese children. Olson and his team tested for correlations between vitamin D levels and markers of abnormal glucose metabolism and blood pressure in a total of 498 obese and non-obese children from North Texas, USA.
The team measured plasma vitamin D levels, blood sugar levels, serum insulin, BMI and blood pressure, and participants were asked to provide dietary information -- including daily intake of soda, juice and milk, average daily fruit and vegetable intake, and whether or not they routinely skipped breakfast.
The team found that 92% of obese subjects had a 25(OH)D level below the 'adequate' levels of 75 nmol per litre, whilst 50% were classed as deficient -- with levels below 50 nmol per litre.
"Poor dietary habits such as skipping breakfast and increased soda and juice intake were [also] associated with the lower vitamin D levels seen in obese children," revealed Olson.
He said that future studies are needed to determine the clinical significance of lower vitamin D levels in obese children.
Olson added that future research should investigate the required amount and duration of 'treatment' necessary to replenish vitamin D levels in deficient children, and whether increasing vitamin D status "can improve primary clinical endpoints such as insulin resistance."
The Journal of Clinical Endocrinology & Metabolism