One of the trendiest diets these days is going gluten-free, but people who have celiac disease don’t have the luxury of cheating once in a while to eat pizza or drink a beer.

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Celiac disease is a serious autoimmune disease that affects more than 3 million Americans.

When a person with celiac eats gluten, a protein found in wheat, barley, and rye, their immune system causes the body to attack itself, specifically the villi in the small intestine. The villi are small, finger-like structures that provide a large surface area for nutrients to be absorbed — unless they’re damaged. According to the Celiac Foundation, the disease can lead to more serious complications down the line, such as deficiencies, infertility, and neurological issues.

I decided to try eating gluten-free for a week to see what a diet might be like for someone with the disease. I quickly discovered that many, many things I assumed were safe to eat were actually a source of potential gluten exposure and, as a result, meals and snacks need careful planning.