Increased safe sun exposure during winter may be one way to reduce fasting blood sugar in children with obesity, Australian research suggests.

A WA-led study in 6-13 year-olds has found markers of glucose metabolism appear to vary with the season – consistent with similar observations in adult populations.

The study comprised 163 children recruited from Perth primary schools and 99 children recruited after a hospital consultation for weight-related issues. Most children (62%) were of normal weight, 30.5% were overweight and 7.3% were obese.

The study used season and local terrestrial UV levels in Perth as proxies for recent sun exposure at the time of the children’s blood samples.

It found fasting blood glucose levels were lowest in autumn and highest in spring for children in the combined, normal and obese weight categories.

“Similarly, we observed an inverse relationship between fasting blood glucose and mean daily terrestrial UVR levels, with a strong significant relationship observed in children with obesity when daily terrestrial UVR levels were measured in the 6 months prior to the blood test,” the researchers said.

In children of normal weight, fasting insulin was significantly higher in winter compared to summer and autumn.

However the evidence was not completely consistent across markers or groups of children. HbA1c was higher in summer than in winter in children in the combined or overweight category but that was not seen in children of normal weight.

The study authors said preclinical studies had suggested a plausible mechanism for the effect of seasonality on blood glucose levels, which might be related to the release of nitric oxide bioactivity following UV exposure of the skin.

Dr Shelley Gorman, program head of diabetes and obesity at the Telethon Kids Institute, told the limbic the research findings were limited by factors such as small numbers of children and blood measures at a single time point per child.

“We definitely think our findings need to be reproduced with more children who have obesity or are overweight,” she said.

“There is some science there that time of year might be really important for modulating glucose and it may be that kids with obesity need to get outside and get a bit of sun in the winter months. But we haven’t really shown that. We’ve just shown associations between season and terrestrial UV and fasting blood glucose levels.”

“There is more work to be done,” she added.

“If sun exposure is an important environmental factor, and our study certainly suggests it might be, then we certainly need to have a closer look in children around Australia and the world.”