She lost all her energy. She developed acne. And she began experiencing gastrointestinal problems: bloating, diarrhea, cramping, constipation. Her doctors, thinking something must be missing from her diet, put her on various vitamins, none of which helped. "It was all I could do to go to work," she says.
After years of failed treatments, Cooper's luck changed. She saw a doctor who suspected she might have celiac disease, an autoimmune disorder that can appear at any age and is caused by an intolerance to gluten. A protein found in wheat, barley, and rye (and countless food productslike bread and pastathat contain those grains), gluten gradually damages the intestines of people with celiac disease, preventing the absorption of vitamins and minerals and setting off a slew of related health problems, which can include fatigue and bad skin.
Cooper tested negative for celiac disease, but the doctor advised her to try a gluten-free diet anyway. "Within a week of eliminating [gluten], I started to feel markedly better," says Cooper, now 36, from Melbourne, Australia. "It wasn't a gradual feeling better; it was almost a crossing-the-street kind of thing."
That was 10 years ago. The general practitioner who treated Cooper was ahead of his time, as most doctors are only now starting to realize that some people who don't have celiac disease may benefit from diets free of (or low in) gluten.
In fact, experts now believe that celiac disease represents just one extreme of a broad spectrum of gluten intolerance that includes millions of people like Cooper with less severebut nevertheless problematicreactions to the protein. While celiac disease affects about 1% of the U.S. population, experts estimate that as many as 10% have a related and poorly understood condition known as non-celiac gluten intolerance (NCGI) or gluten sensitivity.
"This is something that we're just beginning to get our heads around," says Daniel Leffler, MD, an assistant professor of medicine at Harvard Medical School and a gastroenterologist at Beth Israel Deaconess Medical Center, in Boston. "There is a tight definition of celiac disease, but gluten intolerance has been a moving target."
Growing awareness of gluten sensitivity has led some people who struggle with gut problems but have tested negative for celiac disease to take matters into their own hands and try a gluten-free diet, even though it's an extremely difficult diet to follow. Sales of gluten-free products increased 16% in 2010, according to the Nielsen Company.
"Gluten is fairly indigestable in all people," Dr. Leffler says. "There's probably some kind of gluten intolerance in all of us."