Just a decade ago, few people knew what gluten was. Today the wheat protein is having a moment (OK, more like a few years of fame) amidst a sea of grains. The gluten-free diet is one of the trendiest food restrictions in the U.S., with celebrities including Lady Gaga and Zooey Deschanel touting it as their secret to perfect health. Some claim it to be an ideal weight-loss tool, while others say it has given them more energy and helped abate stomach pains and improve digestion.

As a result, almost every popular gluten-containing product—pancakes, brownie mixes, beer—now has a gluten-free alternative. This year, the makers of Girl Scout cookies even announced two gluten-free goodies.

Though the instant popularity has helped ensure that those with celiac disease receive a proper diagnosis (and have plenty of gluten-free food options), the number of people in the United States currently adhering to a gluten-free diet far surpasses the number who suffer from celiac disease. And while some may benefit from avoiding gluten, others may instead hurt their health.

The Elusive Celiac Disease

Meaning “glue” in Latin, gluten is a protein found in wheat, barley, and rye. It’s what gives pizza dough its stretchiness and adds the chewy texture to wheat products such as bagels or al dente pasta.

For people with celiac disease, the body sees gluten as a predator. When ingested, the immune system reacts by attacking the small intestine (where gluten is digested) and generating inflammation that prevents people from absorbing important nutrients. This causes symptoms such as abdominal pain, bloating, weight loss, and fatigue http://www.ncbi.nlm.nih.gov/pubmed/23681421″>http://www.ncbi.nlm.nih.gov/pubmed/23681421http://www.ncbi.nlm.nih.gov/pubmed/20661732″>http://www.ncbi.nlm.nih.gov/pubmed/20661732http://www.ncbi.nlm.nih.gov/pubmed/18803427″>http://www.ncbi.nlm.nih.gov/pubmed/18803427—and it’s why many people with “stomach problems” say they prescribe to a gluten-free diet.

But symptoms alone aren’t enough to diagnose celiac disease. Instead it takes a simple blood test or procedures like an endoscopy, where doctors guide a flexible tube through the stomach and into the small intestine where biopsies are taken to look for a certain type of inflammation.

Those who test negative for the disease yet experience celiac-like symptoms that subside when they go gluten-free may have non-celiac gluten sensitivity (NCGS). While “gluten intolerance” is often colloquially used to describe this condition, doctors and nutritionists say “sensitivity”—which involves an immune response to something you ingested, in this case gluten—is a more accurate term http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3440559/”>http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3440559/: “Intolerance” suggests a person lacks the ability to digest something, explains Alessio Fasano, M.D., head of the Center for Celiac Research at Massachusetts General Hospital for Children in Boston. (Think lactose intolerance, where the body lacks the enzyme to break down lactose.)

Where It Gets Confusing

Regardless of the name, NCGS remains controversial in the medical community. Unlike celiac disease, there is no blood test that can show for sure whether a person is sensitive to gluten. And many of the symptoms—abdominal pain, bloating, and fatigue—are nonspecific and can be attributed to a number of different causes, including stress, food consumed that doesn’t have gluten, or an infection.

Doctors and nutritionists recommend that anyone experiencing these symptoms go see their doctor. It’s important to rule out celiac disease before trying a gluten-free diet, says Leslie Bonci, R.D. director of sports nutrition at the University of Pittsburg Medical Center. If the test comes back negative, it’s common to place patients on a one-month, gluten-free trial diet. This allows the body time to eliminate all the gluten from its system and allows people to evaluate how they feel knowing there is no gluten in their body. After that time, gluten is often reintroduced to see if symptoms return.

If the pain and fatigue does come back, then permanently eliminating gluten may be beneficial, Bonci says. However, because there’s no definitive test and symptoms can be ambiguous, it’s hard to know for sure whether you feel better because you have NCGS or because your new diet is simply healthier—when people stop eating gluten, they also often inadvertently stop eating all those unhealthy cakes, cookies, and processed foods.

Liz Applegate, Ph.D., director of sports nutrition at the University of California at Davis, routinely counsels student athletes on dieting and nutritional needs, and frequently suggests a trial gluten-free diet (once celiac disease has been ruled out). But of the roughly 400 students she advises, she says only two have had celiac disease and none who reintroduced gluten after a trial diet turned out to be sensitive to gluten.

At the same time, recent research suggests there may be a link between patients with irritable bowel syndrome (IBS) and NCGS. In a small 2013 study, people with both IBS and NCGS followed a diet low in FODMAPs—an acronym for a number of fermentable sugars that may be poorly digested or absorbed in the intestines, such as those found in most fruits, dairy, wheat, and legumes. At the end of the trial, only 8 percent of the participants reacted badly to gluten, suggesting that other FODMAPs may be the main culprit. And while the true number of people with NCGS remains unknown, one recent study estimates about 0.5 percent of Americans have NCGS—about half that of celiac disease http://www.ncbi.nlm.nih.gov/pubmed/23834276/”>http://www.ncbi.nlm.nih.gov/pubmed/23834276/.

But All of My Friends Are Doing It

With everything being clear as mud, why is a gluten-free diet one of the most popular food trends in America? Some point to celebrities who’ve said it’s the way to everything from a flat belly to clear skin to an ideal weight. “We see iconic people on these diets and think, ‘If it’s working for this person, it has to work for me,’” Fasano says. But there is nothing about gluten that will necessarily help people lose weight, lower their blood pressure, or prevent disease.

Food companies have also played a role. In 2014, the gluten-free market was estimated to reach sales of $8.8 billion, a 63 percent increase from 2012. The label is everywhere, Bonci says, even on naturally gluten-free foods such as fruit, potato chips, and peanut butter. While that may help heighten awareness of NCGS and celiac disease, it may also be making asymptomatic, healthy consumers think that choosing a gluten-free product is always healthier than choosing its gluten-containing counterpart, Bonci says.

The Takeaway

The gluten-free trend isn’t disappearing anytime soon. Fasano says new studies—taking into consideration IBS, FODMAPs, and especially the gut microbiome (all the microorganisms present in your gastrointestinal tract that help to digest food and perform daily functions)—will hopefully uncover more clues about the mysteries of food sensitivities. But perhaps for now we should listen to our guts—avoiding gluten if need be, but maintaining a healthy diet and lifestyle as the top priority.

If you decide to eliminate gluten, know that the lifestyle can be tough to follow. “Gluten-free does not mean carb-free. The body still needs carbohydrates, and what is replacing those gluten-containing carbohydrates is important,” Bonci says. Many of the gluten-free products on the market today have added fat and sugar to make them taste as similar as possible to their gluten-containing counterparts. Rather than eating these, it’s better to replace wheat products with naturally gluten-free grains such as quinoa, wild rice, and potatoes, and other foods containing carbohydrates including fruits and vegetables, Bonci says.