Celiac disease, a condition resulting from an immune reaction to gluten, continues to increase in the United States, scientists say.

Even considering an increased awareness of the condition and more accurate diagnostic methods, doctors are still encountering more people with gluten intolerance.

Recent work showed an increase in celiac disease among participants in a longitudinal study. The results show that the prevalence of the disease is five times greater now than in 1974, when the data were first collected. Also, the findings suggest that people can develop the disease later in life, too.

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Another analysis using 50-year-old preserved blood samples from a U.S. database showed that the antibodies associated with celiac disease weren't as common in the 1950s when compared to recent decades, as described in a Mayo Clinic release on the research. When compared the samples from the 1950s to recent ones from donors of the same age, researchers found people to be more than four times more likely to have the disease.

In these patients, the immune system launches an attack on the small intestine, targeting areas of the organ's lining called villi that are known to help the body absorb nutrients from food. If left undiagnosed, a person could continue eating gluten in breads, processed foods and some dairy products and become increasingly malnourished.

Even more, these areas can become permanently damaged and unable to absorb nutrients well after a person stops consuming gluten. In some cases, celiac can be deadly if left unnoticed, but the vast majority of cases are manageable.

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Though people's experiences vary, most individuals with this type of gluten intolerance have abdominal pain, digestive issues and even feel constantly fatigued from being malnourished. The disease can also affect people's mental health, especially if they're body lacks certain vitamins and nutrients.

Researchers know that genetics certainly play a role in a person's chance of developing celiac disease, which might be why the condition is relatively common in Europe as well.

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But why the surge in patients living with celiac disease from previous decades?

A few theories claim that an increase in sanitation and better public health may have influenced the trend, according to a HealthDay article. The idea is that as our diets and environments become less diverse, so does the variety of gut bacteria in our intestines. As a result, our intestines may be more vulnerable to conditions such as celiac disease.

Other possibilities point to an increase of gluten in certain plant varieties we've come to depend on or even issues in exposing children with a predisposition to the disease to too much gluten at young ages.