Gluten allergies and sensitivities have been some of the most hot-button issues in the food world over the last couple of years, with gluten- and wheat-free diets booming in popularity despite an often shaky understanding of the science that would necessitate them. And though the research behind various allergies and sensitivities has been evolving, those who suffer from celiac disease have been suffering from well-established markers of the condition for some time.
But while the symptoms of celiac—diarrhea, fatigue, weight loss, anemia, and more—are known and recognizable, the causes of the disease are a bit murkier. People with a celiac family member, or who have diabetes or rheumatoid arthritis, might be more likely to develop celiac, but anyone can, and the disease can also be triggered by a gut infection, a surgical operation, pregnancy, or even emotional stress.
Now, a new study raises an interesting possibility: that people who are born during the winter and in geographical areas with less sunlight throughout the year might be less likely to develop the disease.
A study from a team of Swedish researchers published in the Archives of Disease in Childhood found that Swedish kids who were born in summer, spring, or autumn were 10 percent more likely to develop celiac than their peers born in winter. Moreover, kids born in the south of Sweden, where there is more intense sunlight in spring and summer, were more likely to develop celiac than kids born in the northern part of the country, where warm seasons are shorter and cooler. The risk of celiac increased as the researchers moved from north to south, and girls were more likely than boys to be diagnosed with the disease.
There was also some variation in when children were diagnosed with celiac depending on the specific season in which they were born. Children who developed and were diagnosed with the disease before the age of two were most likely to be born in the spring, while those who were diagnosed later were more likely to be born in summer or autumn.
The study raises a lot of questions about the potential links between seasonality, geography, and celiac disease. Right now, there are only questions, no answers. The researchers are wondering if being born in warm months and being weaned in the fall and winter—when viruses abound—might have something to do with it, as celiac is sometimes associated with certain viral infections.
"One hypothesis for increased [celiac] risk and spring/summer birth is that, those infants are more likely to be weaned and introduced to gluten during autumn/winter, a time characterized by exposure to seasonal viral infections," the researchers wrote.
Another line of inquiry focused on vitamin D deficiency due to a lack of sunlight in the north. Previously, researchers had suggested that vitamin D deficiency might lead to diseases like inflammatory bowel disease and type 1 diabetes—a disease linked with celiac—but the researchers findings, in which northern kids were least likely to have celiac, went against that hypothesis. But they are still questioning whether mothers' vitamin D deficiencies in winter before giving birth in spring could lead to answers, as fetuses' immune systems are largely shaped during later stages of gestation. There's also a question as to whether high exposure to vitamin D might have something to do with it.
The study potentially opens some doors to a better understanding of how people develop celiac in the first place, potentially helping those yet to be born but any major revelatory answers will have to wait. And as for those already with celiac, the study offers little comfort.
Of greater interest would be the Canadian researcher who says he's developed a pill that allows celiacs to eat gluten. Either way, it's up to you, scientists, to find the way forward.