The Link Between Celiac Disease and Type 1 Diabetes

Managing type 1 diabetes is old hat to 31-year-old Catherine Oddenino. The New Yorker has had the disease since she was 11, and is adept at counting carbohydrates and dosing insulin. But in her mid-20s she was thrown a curveball. Whenever she ate something, she felt like she had food poisoning.

After a visit to her doctor, she cut dairy from her diet. But she was also sent to a gastroenterologist who, tipped off by the fact that she had diabetes, immediately tested her for celiac disease. Two weeks later and it was official: the culprit of her “poisoning” was gluten, not dairy.

Now, on top of being keenly aware of how many carbohydrates are in each of her meals and how that will affect her blood sugar levels, Oddenino has to make sure not a speck of gluten is in the food she eats.

Oddenino is by no means the only one living with this dietary juggling act. Study results vary but, according to the American Diabetes Association, an estimated one in 20 type 1 diabetics also has celiac disease. In contrast, the rate in the general population is one in 100.

Diabetes and celiac disease are auto-immune disorders, along with some thyroid diseases, multiple sclerosis and rheumatoid arthritis, among others. This means an overactive immune system causes the body to attack its own cells.

The science is still emerging to explain how type 1 diabetes and celiac disease are related. According to Dr. Alessio Fasano, medical director of the Center for Celiac Research at the University of Maryland, there are two schools of thought: first, the diseases share common genes. A study published in The New England Journal of Medicine in 2008 found almost every gene associated with celiac disease is also involved in type 1 diabetes.

Fasano says another theory is gaining momentum: that some patients have undiagnosed celiac disease which later causes diabetes. While this might seem impossible – typically a celiac disease diagnosis comes long after a diabetes diagnosis – it’s plausible that the celiac disease in these people has simply gone unnoticed.

“You don’t miss [diagnosing] an individual who has diabetes,” says Fasano. In contrast, he estimates that for every person who is diagnosed with celiac disease, at least another 50 aren’t aware they have it. In this “undiagnosed” theory, experts suspect that the chronic “leaky gut” present in celiac patients allows triggers such as food proteins and viral and bacterial particles to enter the body through the intestinal barrier and to reach the space beneath it.

Since a large number of immune cells reside there, this could cause the person to “develop secondary autoimmune conditions, if genetically predisposed,” says Fasano.

Although this “chicken before the egg” question has not been fully answered, the fact remains that most people are diagnosed with celiac disease after already being on a diet for diabetes.

Carbs Can Get Confusing

The transition to a gluten-free diet while keeping blood sugar levels in check is no mean feat, explains Suzanne Simpson, a dietitian at the Celiac Disease Center at Columbia University in New York. She should know: she has worked with many diabetics to introduce a gluten-free diet and lives with both conditions herself.

Gluten-free foods can be significantly different in the amount of carbohydrates they contain. Take spaghetti, for example. Regular wheat noodles contain 23.8 grams of carbohydrate for 150 mL of pasta. Rice spaghetti has 42 grams for the same serving size, almost double. Also, foods can have different amounts of protein and fat, which can delay the rate of absorption of the carbohydrate. “People may end up requiring more insulin – or less insulin,” says Simpson.

Such was the case for Devon Carlson. She, like Oddenino, has had type 1 diabetes since she was a child. It wasn’t until she was 26 that routine blood testing picked up antibodies for celiac disease, which was confirmed with an intestinal biopsy.

As she transitioned to a gluten-free diet her blood sugars quickly went out of whack. “For about three months I was trying all these different [gluten-free] foods, and they add a lot of sugar and fat into them,” recalls Carlson.

The increased fat content caused her body to absorb carbohydrates at a different rate than she was used to, causing her insulin dose to be off. “Once I figured out which gluten-free processed foods I would keep in my diet and stopped trying all these different foods, I got my blood sugar back under control.” She also found that choosing whole foods, such as fruits and vegetables and gluten-free grains, made her insulin dosing a simpler task.

In addition to having to monitor closely how your body’s blood sugar levels will respond to the foods you’re eating, having both celiac disease and diabetes comes with a new set of challenges when dining out and traveling. When she was first diagnosed with celiac disease, Oddenino was in a job where she traveled weekly.

“Traveling with both celiac and diabetes requires thinking ahead in terms of where your next meal is going to be, and what you’re going to have to eat,” she says. While it can always be tricky to find gluten-free foods on the road, having diabetes means you can’t leave anything to chance because eating at regular intervals is key to keeping blood sugars under control.

Simpson agrees. When she travels, she calls the hotel to have a fridge put in her room and, upon arrival, finds out where the closest store is and stocks up on fruit, milk and gluten-free bars and cereal. To Oddenino, this forced planning was actually a blessing: “My colleagues and co-workers would frequently be stuck at some airport fast-food place, and I would have fresh vegetables and meat from my planning ahead.”

You might say Oddenino and Carlson are among the lucky ones, since they got fairly timely diagnoses of celiac disease. In contrast, many people who have celiac disease go undiagnosed for years, because symptoms are often vague (diarrhea, bloating, fatigue, etc.) and many family doctors aren’t aware of how common the disease is.

That’s a concerning issue since untreated celiac disease can increase the risk of osteoporosis, intestinal cancers, neurological disorders and infertility. Because of the strong association between the two autoimmune diseases, increasing numbers of people with diabetes are screened for celiac disease in the United States and Canada which means even those with “silent” celiac disease (they show no symptoms) are getting on the gluten-free diet.

At this point, there’s no reason to test people with celiac disease for type 1 diabetes, says Fasano. That’s because diabetes is easy to spot and likely won’t go undiagnosed. However, he says there is evidence that people who develop type 1 diabetes have certain antibodies long before their diagnosis.

If one day scientists discover a way to slow down the progression toward type 1 diabetes, then screening may make sense. As researchers continue to discover the origins of these two diseases the relationship between them should become clearer. The hope is that diagnoses can be made, allowing more people to live to their healthiest potential.

First published in Allergic Living magazine.