Because we don’t yet know what triggers someone genetically predisposed to celiac disease to actually manifest the disease, I’m fascinated with any study that tries to isolate the different potential variables involved.
A study conducted by the Massachusetts General Hospital for Children and published in the Journal of Pediatrics suggests that children born in the Spring or Summer are more likely to develop celiac disease than those born in Winter or Fall. The study also corroborates a relatively recent theoretical model that integrates certain environmental factors — namely timing of gluten introduction, vitamin D levels and ultraviolet-B exposure — and early childhood gastrointestinal infections. It also corroborates a previous Swedish study published in the Journal of Epidemiology and Community Health, which found that children born in the summer have an increased risk for celiac disease.
One doctor involved in the study, Dr. Tanpowpong, suggested this might help parents prevent some cases of celiac disease: “If your [child is] born in the spring or the summer, it might not be appropriate to introduce gluten at the same point as someone born in the fall or winter. Although we need to further develop and test our hypothesis, we think it provides a helpful clue for ongoing efforts to prevent celiac disease.”
Some researchers hypothesize that this may be because infants born during the light months, March through August, will have solid foods introduced to them during the dark months, specifically during the cold and flu season. This would mean that the introduction of solid foods, including gluten, would happen when the child’s vitamin D levels are lower (less sunlight) and the child is more likely to be exposed to seasonal infections.
Many people think the variation of gut bacteria during the introduction of solid foods and gluten may have something to do with what triggers celiac disease, and viral or bacterial infections can introduce changes to gut bacteria. Recent research also suggests vitamin D and intestinal flora have more of an intertwined relationship and function than previously understood.
To further corroborate theories involving gut bacteria, other studies have suggested that babies breastfed for a longer period of time are less likely to develop celiac disease, and this may be related to the unique probiotics provided by breast milk, such as Lactobacillus reuteri. Additional research even suggests that supplementing with L. reuteri, along with vitamin D, can help improve vitamin D levels in people with a vitamin d deficiency.
At this point this is mostly conjecture and correlation, but it suggests some kind of environmental trigger relating to both vitamin D and gut bacteria may influence the risk for developing celiac disease. I believe research into vitamin D and the human microbiome may do more than reveal the origins and causes of celiac disease; it may ultimately reveal the origins and causes of a number of autoimmune diseases.