What month were you born in? How close to the equator do you live? Answering these two questions could help determine, surprisingly, your risk of getting celiac disease, according to a new Swedish study. Why? It turns out even our pitch-dark bowels are affected by light.
One in 100 people have celiac disease, an autoimmune disorder that makes it hard for the body to digest gluten and damages the small intestine. Rates have been rising in recent years, although researchers haven't really known why. But now a large study, published in BMJ, may have given a new clue in the gluten puzzle: Sunlight exposure as a child.
Researchers examined data from nearly 2 million Swedish children, with 6,600 being diagnosed with celiac disease before age 15. They found that people born during the sunnier months, particularly springtime, were more prone to getting celiac disease. By the same token, people who lived in sunnier climates (i.e. farther south, closer to the equator) also had higher incidences of the disease. Overall, extra sunshine increased the risk of celiac disease by 10 percent.
These findings, while weird, are the easy part—explaining them is much harder.
The differences in sunlight due to season and geographic location may influence the number or type of viruses in the environment, as well as vitamin D production—both of which play an important role in immune system development in children, said Fredinah Namatovu, the lead author and a public health researcher at the Umea University in Sweden. She speculated that an excess of either of these factors may set children's immune systems into overdrive, causing them to attack healthy body cells—which is what happens in a variety of autoimmune illnesses, including celiac.
This research adds to what we already know about potential causes of this gastrointestinal illness, including other risk factors like a family history, certain genetic markers, other autoimmune problems, race, ethnicity, and diet during infancy and childhood.
It should be noted, however, that the study was observational, meaning that all we can say is that there appears to be a link between sunlight and celiac disease—not that one causes the other—and more research needs to be done. But the scientists mentioned that this connection may mean that as earth temperatures continue to rise due to global warming, we may also see a correlated rise in celiac cases.
In the meantime, if you are experiencing any gastrointestinal problems like diarrhea, bloating, pain, and unexplained weight loss, you should see your doctor about getting tested for celiac disease—especially if you were born between April and September in a sunny place.