In a just-concluded trial, Farid Mahmud, MD, of the Hospital for Sick Children at the University of Toronto, described, along with his colleagues, an emerging “double diagnosis” of type 1 diabetes (T1D) and celiac disease (CD) and concluded that celiac disease is “frequently” asymptomatic and undiagnosed in people with T1D. They also reported the surprising finding that T1D patients who switch to a gluten-free diet might experience blood sugar spikes after meals.
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Celiac disease is, like T1D, an autoimmune disease. People who are genetically predisposed to celiac disease suffer damage in the small intestine when they ingest gluten, which is a protein found in wheat, rye, barley, and certain other grains. Celiac disease is estimated to affect about 1% of the world’s population, and it commonly goes undiagnosed. The condition has become talked about more in recent years because of the vogue for “low-gluten” or “gluten-free” diets, the benefits of which are well established for people with celiac disease but which are questionable for people without it.
As the authors of the new study explained, “CD and T1D share common genetic origins and an increasing body of evidence identifies this intestinal insult as a provocative factor in the pathogenesis of T1D and other autoimmune conditions.” They also noted, “it is important to emphasize to clinicians caring for pediatric patients that CD appears at a much higher rate in patients with diabetes and can present with multiple gastrointestinal and nonintestinal features.” As a result, the researchers designed their study to shed light on the “benefits and harms of screening and treatment in asymptomatic persons, especially in the context of type 1 diabetes.”
Their research project was called the Celiac Disease and Diabetic-Dietary Intervention and Evaluation Trial. They screened 1,298 adults and 1,089 children with T1D for celiac disease — at the onset of the trial none of the subjects showed any symptoms of CD. After identifying 51 participants with asymptomatic celiac disease, the researchers randomly assigned them to one of two groups: one that went on a gluten-free diet for a year and a second that continued on a regular diet for the same time period. The subjects’ HbA1C levels were measured at the beginning of the study and again after 6 and 12 months. Blood sugar levels after meals were determined by continuous glucose monitoring. Any participant in the regular-diet group who developed symptoms of celiac disease during the trial was transferred to the gluten-free group.
The researchers found that asymptomatic celiac disease was 1 1/2 times more common in the adult participants than in the pediatric patients, a finding they called “surprising” and probably because the adults had had “lower rates of prior screening overall.” They added, “This may reflect a misperception of celiac disease as a condition exclusively seen during the pediatric period.” The most unexpected finding was that those subjects who were on the gluten-free diet experienced noteworthy increases in blood sugar levels after meals — more than those on the regular diet. And over the 12 months of the study there was a 0.3% increase in HbA1C levels in the gluten-free group.
The researchers concluded that “clinical vigilance” is necessary for T1D patients who adopt a gluten-free diet because such a diet “may impact short-term glycemic variability.” They further pointed out that a gluten-free diet can be a challenge for people with type 1 diabetes because they already face problems dealing with daily dietary issues. “Diabetes,” they wrote, “is a challenging condition requiring daily efforts to balance meals, activity and insulin to maintain adequate metabolic control…. The impact of an additional chronic disease, such as CD, may substantially affect the quality of life in such patients.” Finally, the researchers said, “Maintaining a strict GFD [gluten-free diet] in addition to a diabetic diet requires additional time effort, and expense. It is not surprising that most T1D patients struggle with strict adherence to a GFD.”