First off, gluten is a protein found in wheat, rye and barley, along with related products such as spelt and kamut. Celiac disease is a digestive and autoimmune disorder in which people develop antibodies to gluten. This causes inflammation and damage to the intestines.

“Some people can be very sick, while others have minimal or virtually no symptoms,” explains Peter Green, MD, director of the Celiac Disease Center at Columbia University. Physical symptoms include diarrhea, thinning of the bones, skin rashes, neurological problems, seizures and a host of other issues.

Celiac disease can occur at any age after someone starts to ingest gluten, and it strikes men and women in equal degrees. “But women get diagnosed much more frequently than men because they have greater access to health care and see doctors all the time as compared with men,” Green says.

In addition, some people are sensitive to gluten and often exhibit gastrointestinal symptoms such as bloating, diarrhea and fatigue. “But gluten sensitivity is typically more of a self-diagnosed condition,” Green says. It’s not the same as having celiac disease.

Many people follow gluten-free diets because they feel it’s healthier—but that ain’t necessarily so. “Gluten-free diets are low in fiber,” Green explains, “and rice flour, which is the main substitute for wheat flour, isn’t fortified.”

What’s more, most people on a gluten-free diet may develop vitamin and iron deficiency.

Advises Green: “So if people are going on a gluten-free diet, they should get advice from an experienced dietitian and make sure that their gluten-free diet is healthy.”