ROCHESTER, MINN. — The number of Americans who avoid gluten even though they do not have celiac disease more than tripled from 2009-2014, increasing to an estimated 3.1 million people, according to a study in the January issue of Mayo Clinic Proceedings.

Researchers at the Mayo Clinic in Rochester used a sample comprised of 22,227 people age 6 or older in the National Health and Nutrition Examination Surveys for their study. The prevalence of Americans without celiac disease who avoid gluten increased to 1.7% in 2013-14 from 1% in 2011-12 and 0.5% in 2009-10.

The study concluded long-term health consequences of a gluten-free diet warrant further investigation.

The benefits of following a G.F.D. (gluten-free) diet in people without C.D. (celiac disease) have not been tested rigorously, and indeed nutritional concerns have been raised about deficient iron, calcium and fiber consumption,” the study said. “In contrast to public interest in following a G.F.D., it remains uncertain whether there is any benefit of following a G.F.D. for people without gluten-related conditions.”

The gluten-free diet is prescribed for gluten-related conditions, including celiac disease (an autoimmune disease) and wheat allergy.

In the Mayo Clinic study, the prevalence of celiac disease stood at 0.7% of the U.S. general population, or about 2 million Americans, in 2013-14, which compared to 0.8% in 2011-12 and 0.7% in 2009-10. The prevalence of people with undiagnosed celiac disease dropped to 0.3% in 2013-14 from 0.6% in 2009-10.

“Interestingly, the prevalence of undiagnosed C.D. decreased significantly in this period, suggesting a success in detection, an increased awareness of C.D. or maybe an increasing preference for a G.F.D.,” the study said.

The Centers for Disease Control and Prevention and the National Institute of Diabetes and Digestive and Kidney Diseases partly supported the study.