Celiac disease is not an allergy. It is an autoimmune disease where the body produces antibodies that attack and destroy the epithelium, or cell lining, of the small intestines, according to the National Institutes of Health (NIH). Celiac is a chronic and incurable disease, and the only treatment for patients is to follow a strict gluten-free diet.

A blood test for tissue transglutaminase (TTG) antibodies is just the first step. A celiac disease diagnosis is only positive after a biopsy. This requires an upper endoscopy where several tissue samples are taken from the small intestines to be examined by a pathologist, according to the Celiac Disease Foundation. Depending on the type of damage seen, celiac will either be ruled out or identified.

Contrary to popular belief, Dr. Guandalini says, the gluten-free diet isn’t the healthiest. He doesn’t recommend it for those who don’t have celiac disease. It can cause constipation from lack of fiber and also limits the intake of vitamins and minerals. The problem is many people switch to manufactured gluten-free products, he says, which are refined, highly processed, and lacking nutrition. Some gluten-free flours are not fortified with the same vitamins contained in wheat.

“Celiac” and “gluten” seem ubiquitous today. In reality, only 1 in 141 people in the United States have celiac disease, according to the NIH. However, many people with celiac disease are undiagnosed.

Some of the typical symptoms of celiac disease are GI-related — bloating, constipation, gas — but doctors are now realizing there is an array of other symptoms, too. Dr. Guandalini says these non-GI symptoms are becoming just as prevalent, if not more so, than the typical symptoms. They include anemia, recurring headaches, arthritis and osteoporosis.

Gluten comprises two major components: glutenins and gliadins, both of which – and especially the former - are toxic for celiac individuals. In addition, secalin from rye and hordein from barley, contain toxic fragments similar to gliadins.

Gluten is not in all grains, as is commonly mistaken. People with celiac can eat rice, potatoes, quinoa, and buckwheat. But they must avoid wheat, couscous, and spelt, among many others. Always read ingredient labels. If you’re out to eat and you’re unsure if something is gluten-free, skip it.

While there may be some people who are both celiac and lactose intolerant, this is not usually the case. To repeat, people with celiac need only to refrain from wheat, barley, and rye. People with celiac can consume all dairy products, meat, vegetables, and fruit unless they have other unrelated food allergies or intolerances unrelated to celiac. So there are still plenty of food options to complete a healthy diet full of variety.

Hate to be the bearer of bad news, but chances are it’s not gluten packing on the pounds. It's true people lose weight when they stop eating pizza, pasta, and bread. But those foods are also high in calories and carbs. Many gluten products are high glycemic-index foods, such as cake, cookies, and muffins. If you’re looking to lose weight, talk with your doctor or a nutritionist for the right diet to follow.

Gluten can be found in a lot of unexpected places other than food. Medicine, toothpaste and cosmetics can contain gluten. Learn about other surprising products that may have gluten. Ask your doctor for more information on what to avoid.