Sunshine and Inflammatory Bowel Disease

A recent provocative study (EA Holmes et al. JPGN 2019; 69: 182-88) describes an inverse association between sunshine exposure and the development of pediatric inflammatory bowel disease (IBD).  Among a cohort of 99 children with IBD and 396 controls, the authors used questionnaires to estimate past sun exposure along with other variables.

Key finding:

  • “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 (P=0.002)”

There was no corresponding data with regard to vitamin D status.

My take:  Being active and going outside are likely good for one’s health and there have been other studies suggesting more sun exposure could reduce the rate of Crohn’s disease. Does Sun Exposure Lower the Risk of Crohn Disease? | gutsandgrowth  Despite this, in my view, this study’s findings have limited value.

  1. There may be many confounders that separate children with more sun exposure from those with less exposure, including diets, exercise, camping, exposure to animals and soil, and many other variables. In addition, there may have been problems with recall bias.
  2. The role of vitamin D was not studied. In previous studies, the importance of vitamin D in its effect on the IBD/immune system have yielded inconsistent results.
  3. In those with IBD, suggesting that more sun exposure may have prevented IBD would not be helpful; this is due to the flimsy evidence and this information could be interpreted  as blaming the family.
  4. Correlation does not prove causation.  For example, a far-fetched association of correlation that is not likely to have a causal association: Rates of Drowning by Falling in Pools and Nicholas Cage Films (National Geographic: Nicholas Cage Movies vs. Drownings)

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View from Wahkeenah Falls Trail, OR