Higher sun exposure (vitamin D) linked to lower risk of IBD in children

Children exposed to the sun in the previous winter or summer are at lower risk of developing inflammatory bowel disease (IBD), according to a recent study published in the Journal of Pediatric Gastroenterology and Nutrition. The researchers suggest that this may be mediated by sunshine vitamin, vitamin D.

The occurrence of pediatric inflammatory bowel disease (IBD) is increasing worldwide. Ecological studies have shown a higher occurrence of the disease in the regions having less exposure to the sunlight. However, no studies until now have assessed individual-level associations with sun exposure. Elizabeth Ann Holmes, from the Australian National University in Canberra, and colleagues conducted the study to assess the relationship between sun exposure and incidence of pediatric IBD.

For the purpose, the researchers recruited 99 children (ages 0 to 17 years) with IBD from two large hospitals in Melbourne, Australia, as well as 396 control participants from the day surgery unit of one of the hospitals. Surveys assessed demographics, previous sun exposure, the likelihood of sunburn (skin sensitivity) or tanning following sun exposure, use of sun protection, physical activity, and parental smoking and education.

Key findings of the study include:

• In multivariable analysis, for each 10 min increment in leisure-time sun exposure in summer or winter there was a linear 6% reduction in the odds of having IBD.


• Results were similar in sensitivity analyses including only the most recently diagnosed cases, only Caucasian cases and controls, only those with symptom onset within the year prior to study entry, or additionally adjusted for age or physical activity.

"We were unable to explore the mechanism of this effect, and the possibility that it may be mediated by vitamin D," write the authors. "These findings add to growing evidence that higher sun exposure (or vitamin D) is associated with reduced risk of some autoimmune diseases; if replicated, this may provide an avenue toward prevention or reduction in incidence."