Gluten-free eating is a trend that doesn’t show signs of stopping. Anywhere from 17 to 40 percent (depending on the poll) of American adults actively avoid or reduce gluten in their diets. And as gluten-free options expand on store shelves and restaurant menus—and become increasingly tasty—more people wonder if they should join the swell. Here we dig deep into the science—quizzing the experts and examining the studies—to discover if gluten-free eating is a healthy lifestyle that should extend to the masses (including you!) or be reserved for the few.

Status: It’s Complicated

The short answer: There’s no short answer. Experts disagree, often vehemently. They interpret research differently and draw on different sources. The list of things they do agree on is short:

  • Many people feel better when on a gluten-free diet, even if they don’t have celiac disease. Experts differ as to why, but studies back it up, as do many people’s real-life experiences.
  • A gluten-free diet isn’t automatically a healthy diet—and it shouldn’t be done to lose weight. Read on for details.
  • There’s a lot we still don’t know. Many questions about the effects of gluten remain unanswered, and nearly all experts conclude that much research remains to be done.

In the meantime, we offer this basic gluten primer, including how top authorities weigh in on whether or not you should avoid gluten. A teaser: Foods with gluten can be more of a problem than you probably think—and for different reasons than you might expect.

What’s the Big Deal About Gluten?

More than half of Americans can’t define what gluten is, according to a 2015 survey by gluten-certification organization NSF International. Here’s the scoop: Gluten is a mixture of proteins found primarily in wheat, barley and rye. Gluten proteins divide into two main categories: gliadin and glutenin. When digested, these proteins break down into many different peptides, essentially strings of amino acids.

The trouble starts because our digestive systems can’t fully break down all of these peptides, so they remain macromolecules. In some people this becomes a big problem, especially those with certain genes. In people with celiac disease (CD), an autoimmune disorder found in at least one percent of the population, these macromolecules trigger the immune system to attack the lining of the small intestine, destroying tiny, fingerlike projections called villi and making the intestine too permeable (everyone’s intestine is somewhat permeable, which is how we absorb nutrients). The casual name for this is “leaky-gut,” and it eventually leads to malnutrition.

“When someone with celiac is eating gluten, gluten damages the lining to your small intestine, so you’re not absorbing the nutrients—the vitamins and minerals—that you should be if you’re eating a healthy, balanced diet,” says Talia Hassid, communications manager for the Celiac Disease Foundation. People with CD are more prone to developing other autoimmune diseases, and the risk goes up the later in life one is diagnosed, according to a classic study in Gastroenterology. There is no known cure for CD, and the only treatment is a strict, lifelong adherence to a gluten-free diet.

Beyond CD, which is relatively well researched and understood, the waters start to get a bit murky. Some studies—many of which are summarized in a 2013 academic review published in Nutrients— have shown that gliadin (gluten) consumption can produce an inflammatory and immune response, and temporarily raise intestinal permeability, even in healthy people without CD. Consequently, a 2012 report in BMC Medicine concluded that because of the high levels of gluten in modern wheat and the sheer quantities of wheat consumption in Western societies, “all individuals, even those with a low degree of risk, are therefore susceptible to some form of gluten reaction during their life span.” But in those with CD—and in some people who don’t have the small-intestine damage required for a CD diagnosis—the effects are more pronounced.

Science increasingly points to a spectrum of gluten disorders, the most common of which are CD, wheat allergies and a less-understood category called Non-Celiac Gluten Sensitivity (NCGS)—or, alternatively, Non-Celiac Wheat Sensitivity (NCWS). People with NCGS don’t exhibit the same intestinal damage or blood-test markers as those with CD, or the same blood-test markers as those with wheat allergies, but they still exhibit symptoms when eating gluten—and reduced symptoms when on a gluten-free diet. These symptoms may include gastrointestinal (GI) troubles—such as diarrhea, bloating, indigestion or constipation—and other maladies like headaches, joint pain, rashes, unclear thinking, fatigue and even depression, ADHD-like symptoms or infertility.

Both CD and NCGS can affect “every organ in your body,” Hassid says. No specific biomarkers for NCGS have been agreed upon, so it’s impossible to say how many people it may affect, although some experts suspect numbers as high as 30–40 percent of the population. But help for setting biomarkers may be on its way: A ground-breaking Italian study published in July in the journal Gut discovered that, like CD, NCGS is also likely an autoimmune disorder. Researchers reported that for people with NCGS, wheat causes different intestinal damage than is found with CD and triggers a systemic immune response that results in elevated levels of different antibodies than someone with CD exhibits.

The verdict is still out as to exactly what causes NCGS, but research now suggests that gluten might not be the only culprit. Other proteins might also be to blame, and a widely reported Australian study found that, for GI symptoms, the primary problem might actually be a sensitivity to highly fermentable (read: gas-producing) carbohydrates called FODMAPS, which are found not only in wheat and rye, but also in dairy, and some fruits and vegetables (see What Are FODMAPs?). The study’s authors suggested that gluten may be mostly responsible for NCGS’s non-GI-related symptoms. Other research, including the BMC Medicine report mentioned above, also supports this theory.

How to Know If You’re at Risk

It’s not easy. For starters, even people with CD may not exhibit symptoms for many years. Certified clinical nutritionist Tom O’Bryan—an instructor at the Institute for Functional Medicine and founder of The Gluten Summit, which assembled 29 of the world’s top gluten authorities—describes it this way: A cheesecloth-like coating covers your small intestine’s villi; every time you eat gluten, you tear the cheesecloth a bit, but it regenerates.

“You have rolls for breakfast—you tear the cheesecloth, and it heals. You have a sandwich for lunch—you tear the cheesecloth, and it heals. You have pasta for dinner—you tear the cheesecloth, and it heals,” O’Bryan says. “Day after week after month after year, until one day—it can be when you’re 2 years old, it can be when you’re 22 years old, it can be when you’re 72 years old—but one day, you cross that imaginary line, and you don’t heal anymore. Now you get pathogenic intestinal permeability, which is the gateway into the development of autoimmune diseases.”

At that point, autoimmune issues can manifest in any part of your body—leading to anything from multiple sclerosis or Alzheimer’s to thyroid issues or arthritis, whatever the weak link in your body’s chain is, O’Bryan says.

A blood test and subsequent intestinal biopsy can confirm if you have full-blown CD (but only if you’re not already on a gluten-free diet, says Hassid of the Celiac Disease Foundation). A blood test can also determine if you have a wheat allergy. A genetic test can indicate whether you’re at a higher risk for CD or possibly NCGS, but it’s not necessarily definitive. Unfortunately, no test currently exists to determine if you have NCGS.

So What Can You Do?

The first step if you suspect you might be sensitive to gluten is to ask your health practitioner to test you for celiac disease and wheat allergies. (For other testing suggestions, see “Cutting-Edge Tests.”). If the results are negative, consider trying a gluten-elimination diet, but only under supervision of a physician or dietitian. “It’s important to be wary of potential nutrient deficiencies when cutting out gluten, because you’re cutting out significant sources of fiber, B vitamins and iron, in particular,” says Lisa Cimperman, a spokesperson for the Academy of Nutrition and Dietetics and a registered dietitian at University Hospitals Case Medical Center in Cleveland, Ohio. (See “Boost Your Gluten-Free Diet” for naturally gluten-free foods rich in these nutrients.) Also, if your symptoms are primarily GI-related, ask your doctor about trying a low-FODMAP diet (this can be especially dangerous without supervision, because it eliminates even more foods).

Also, don’t fall in the trap of equating “gluten-free” with “healthy.” Just because a doughnut or pretzel is gluten-free doesn’t mean it’s good for you, warns holistic nutrition counselor Elizabeth Stein, founder and CEO of gluten-free food company Purely Elizabeth. Stein recommends first educating yourself about good nutrition. “Get rid of that mindset of reading a label to see if it’s labeled gluten-free versus reading a label to see if it has good-quality ingredients,” she says. “If you’re eating a wrap made out of quinoa flour versus white rice flour, of course the quinoa flour is going to be healthier and have more fiber and be more nutrient-rich.”

Cimperman agrees. “We recommend the same concepts [for those going gluten-free] as for individuals who are not on a gluten-free diet: a diet that is rich in unprocessed foods and foods that come from plants,” she says. She also suggests supplementing with a multivitamin to counteract nutrient deficiencies.

Nearly all experts caution against going gluten-free for weight-loss purposes, especially without a doctor’s supervision. Some people who go gluten-free actually gain weight, Hassid says—sometimes because, if they have CD, they gain weight as their gut heals and they start absorbing nutrients again, and other times because they swap their usual gluten-full foods for gluten-free junk foods that may have even more calories and sugar.

If you do go gluten-free, use it as an opportunity to clean up all aspects of your diet, Hassid suggests. “For some people, once they cut gluten out of their diet, it forces them to be more aware of what else they’re putting in their mouth because they’re constantly reading ingredients. So if you’re looking for one thing, you may start looking for other things. It makes you more aware and more cautious of what you put into your body.”