Celiac disease is an autoimmune condition characterized by an intolerance to gluten - a protein naturally present in wheat, rye, and barley, and which acts as a "glue" in foods such as bread, cereal, and pasta.
When an individual with celiac disease consumes foods containing gluten, the body's immune system attacks the small intestine, damaging finger-like projections called villi, which are important for absorption of nutrients from food.
The only way for people with celiac disease to avoid these symptoms is to adopt a gluten-free diet, but - as the new study affirms - it seems that even people without the condition are moving toward a preference for gluten-free foods.
The gluten-free diet has gained enormous popularity in recent years; according to market research company NPD, around 26-30 percent of adults in the U.S. claim to be reducing their gluten intake or avoiding gluten completely, despite not being diagnosed with any form of gluten sensitivity.
This dietary shift has been attributed to studies that claim avoiding gluten can have significant benefits for the average person, such as weight loss and reduced risk of cardiovascular disease. The gluten-free diet has even been touted by celebrities, including Gwyneth Paltrow and Jenny McCarthy.
Some studies, however - such as one published in the journal Gastroenterology in 2013 - claim that a gluten-free diet has no health benefits for people without celiac disease.
Assessing prevalence of celiac disease, adherence to gluten-free diet
For this latest study, co-author Dr. Hyun-seok Kim, of Rutgers New Jersey Medical School in Newark, and colleagues set out to determine the prevalence of celiac disease in the U.S. in recent years, as well as adherence to a gluten-free diet.
Fast facts about celiac disease
- Celiac disease is estimated to affect 1 in 100 people across the globe
- The condition can arise at any age
- Celiac disease is hereditary; people with a first-degree relative with the condition have a 1 in 10 chance of developing it themselves.
The team assessed 2009-2014 data from the National Health and Nutrition Examination Surveys (NHANES), which included 22,278 individuals aged 6 years and older.
Diagnosis of celiac disease among participants was established through blood tests, and information on adherence to a gluten-free diet was gathered through interviews.
A total of 106 (0.69 percent) participants were diagnosed with celiac disease during the study period, the team found, while 213 (1.08 percent) subjects reported following a gluten-free diet, despite not receiving a diagnosis of celiac disease.
Applying these numbers to the U.S. population, the team estimated that 1.76 million people have celiac disease, and 2.7 million people without celiac disease adhere to a gluten-free diet.
Looking at the prevalence of celiac disease over the 6-year period, the researchers found it remained steady; prevalence was 0.70 percent in 2009-2010, 0.77 percent in 2011-2012, and 0.58 percent in 2013-2014.
However, adherence to a gluten-free diet among individuals without celiac disease increased over the same period, with 0.52 percent following a gluten-free diet in 2009-2010, 0.99 percent in 2011-2012, and 1.69 percent in 2013-2014.
The researchers note that the small number of NHANES participants diagnosed with celiac disease is a major limitation, as is the small number of people without the condition who reported following a gluten-free diet.
Why are more people going gluten-free?
The team says it is possible that adherence to a gluten-free diet has increased because gluten has been identified as a risk factor for celiac disease, and in turn, this could explain why prevalence of celiac disease has not risen.
However, the researchers say it is also possible that more people without celiac disease are adopting a gluten-free diet because of widespread perceptions that it is healthier.
What is more, greater availability of gluten-free products may have also spurred greater adherence to a gluten-free diet.
"[...] there is also an increasing number of individuals with self-diagnosed gluten sensitivity but not the typical enteropathic or serologic features of celiac disease who have improved gastrointestinal health after avoidance of gluten-containing products," the authors add.
In an editorial linked to the study, Dr. Daphne Miller, of the Department of Family and Community Medicine at the University of California-San Francisco, says these findings should not dismiss gluten-free as a beneficial diet for people without celiac disease.
"Although the choice to be gluten-free may be driven in part by marketing and a misperception that gluten-free is healthier, it is important that this choice not be dismissed as an unfounded trend except for those with celiac disease and wheat allergy," she notes.
"Instead, researchers and clinicians can use this as an opportunity to understand how factors associated with this diet affect a variety of symptoms, including gastrointestinal function, cognition, and overall well-being."
Time trends in the prevalence of celiac disease and gluten-free diet in the us population: Results from the National Health and Nutrition Examination Surveys 2009-2014, Hyun-seok Kim et al., JAMA Internal Medicine, doi: 10.1001/jamainternmed.2016.5254, published online 6 September 2016, abstract.
JAMA news release, accessed 5 September 2016 via EurekAlert.
Celiac Disease Foundation, What is celiac disease?, accessed 5 September 2016.
No effects of gluten in patients with self-reported non-celiac gluten sensitivity after dietary reduction of fermentable, poorly absorbed, short-chain carbohydrates, Gibson PR. et al., Gastroenterology, doi: 10.1053/j.gastro.2013.04.051, published online 5 September 2016, abstract.
NPD, Is gluten-free eating a trend worth noting?, accessed 5 September 2016.