Scientific Reports: Sunlight Exposure Linked to Lower Blood Glucose Levels and Reduced Risk of Diabetes

Exposure to sunlight is associated with lower blood glucose levels and a reduced likelihood of developing type 2 diabetes, according to researchers from the University of Edinburgh in the UK and Karolinska Institutet in Sweden. The findings were published in the journal Scientific Reports.

The researchers analyzed data from participants in the UK Biobank project collected between 2006 and 2010. To assess short-term exposure to sunlight, they used data on average levels of ultraviolet A (UVA) radiation in the participants’ residential areas during the two and seven days preceding their blood tests. Long-term exposure was assessed based on participants’ reported frequency of using tanning beds.

The analysis revealed an inverse association between UVA exposure and blood glucose levels. Higher average sunlight exposure over a two-day period was associated with lower blood glucose levels during the winter. When a seven-day period was analyzed, the same association was observed in both winter and spring.

The assessment of long-term exposure also revealed a link with the risk of developing type 2 diabetes. People who occasionally used tanning beds had a 14% lower likelihood of developing the disease compared with those who did not use them. Among frequent users, the reduction was 22%.

More frequent tanning-bed use was also associated with a lower body mass index and lower blood glucose levels, as well as higher vitamin D levels. However, the researchers emphasize that these findings do not mean tanning beds should be used to prevent diabetes.

The scientists suggest that some of the effects of sunlight may be related not to vitamin D, but to other biological mechanisms. Exposure to ultraviolet radiation activates nitric oxide in the skin, which can dilate blood vessels. Previous studies have also suggested that this mechanism may influence blood flow, insulin sensitivity and insulin secretion.

The association was particularly pronounced during winter, when ambient UVA levels are relatively low. The analysis showed that at lower levels of exposure, increases in sunlight exposure were accompanied by the most noticeable reductions in blood glucose levels.

The authors emphasize that the findings demonstrate an association rather than a proven cause-and-effect relationship. Further research is needed to better understand the underlying mechanisms and determine whether sunlight exposure can actually influence the risk of developing diabetes.