The war on gluten can be seen on restaurant menus all over America, but is there a scientific or medical basis for such widespread gluten discrimination?

It depends on whom you ask, but there's certainty in the medical community that uncertainty remains about non-celiac gluten sensitivity.

There have been many studies on the concept that have determined its validity, while others are less clear, said Tracey Wall, a physician's assistant with Memorial Regional Health.

"In my experience, there are people out there that do better restricting some gluten in their diet, but no scientific reasoning for this has been found as of yet," she said.

Celiac vs. gluten intolerance

Celiac disease, an autoimmune disorder that primarily affects the small intestine, is the most severe of the body's reactions to gluten. It affects about 1 in 141 Americans, according to the National Institute of Diabetes and Digestive and Kidney Diseases. Celiac disease is diagnosed after a blood test and sometimes also a biopsy of the small intestine, Wall said.

Gluten, a protein found in wheat, barley, rye, also pops up in various processed foods, medicines, vitamins and supplements. An intolerance or sensitivity to gluten is estimated to affect about 0.5 to 13 percent of the population, but there are no diagnostic tests that can definitively identify the condition. Symptoms are similar to celiac and can include diarrhea, stomach pain, tiredness, bloating and depression.

"The discovery (of gluten intolerance) is often made by going on an elimination diet and figuring out what triggers a patient's symptoms," she said. "Other times people know they are sensitive to gluten without any specific elimination diet because they know that after they eat certain foods containing gluten they feel ill. People who have general bowel issues might consider eliminating gluten from their diet to see if this helps their symptoms if they have had a negative medical work-up for other more serious issues."

Celiac disease is genetic. People are born with a predisposition to the disease that can manifest at different times in their life, Wall said.

Some people with celiac do not have digestive symptoms and instead exhibit tiredness or anemia, making celiac a hard disease to diagnose. About 1.4 million people — out of the estimated 1.8 million who have the disease — don't know they have it, according to a 2012 study published in the American Journal of Gastroenterology.

Another study looked at 400 people with self-diagnosed gluten intolerance and investigated whether they improved on a gluten-free diet. Only 55 people of the 400 actually had issues with gluten — 26 of them had celiac disease, 2 had a wheat allergy and 27 were diagnosed as gluten insensitive.

Is gluten unhealthy?

As for whether gluten is bad for us, research is inconsistent, Wall said. For some people, gluten can cause inflammatory issues, but most people can digest gluten without any issues.

"Going on a gluten-free diet is not necessarily 'better.' It is more difficult to eat whole grains, at times, on a gluten-free diet," Wall said. "Just because a food says it is gluten-free does not mean that it is healthy. Many gluten-free foods are full of sugar and other processed foods that we know to be harmful in large quantities. Good education on nutrition is really important before choosing this type of diet."

Wall said she doesn't typically recommend that patients restrict gluten if there's no evidence of sensitivity to it. Evidence doesn't show that restricting gluten provides any obvious health benefits, she said.