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Gluten Intolerance: What You Need to Know

Gluten intolerance encompasses a range of conditions. The most severe form of gluten intolerance is celiac disease, but less severe forms exist, too. Here’s what you need to know if you think you might be gluten-intolerant or gluten-sensitive.


Butternut Squash Carbonara with Broccoli

Gluten, a protein in wheat, barley and rye, has been on the receiving end of a lot of dietary flak recently. As awareness about gluten sensitivity and intolerance rises, so do questions about what these conditions are and whether you might have them.

Many people are self-diagnosing themselves as gluten-intolerant based on a long list of seemingly unrelated symptoms: brain fog, depression, chronic fatigue, headaches, abdominal pain, bloating and joint pain. With more friends opting for the gluten-free buns at dinner, you may be wondering if it is really possible to be “sensitive” to gluten? And, if so, how do you know you are, especially when these symptoms sound so generic and also common?

It’s time to separate facts from fiction around gluten sensitivity.

What Is Gluten Intolerance?
Gluten intolerance is a newly recognized and poorly understood disorder. There is no official definition of gluten intolerance, but, clinically, many experts call it nonceliac gluten sensitivity (NCGS). Patients with NCGS experience symptoms similar to those that occur in people with celiac disease—a condition in which the body’s immune system reacts to gluten by producing inflammation and damage to the intestinal lining. Those symptoms can range from abdominal pain, bloating, gassiness, nausea and diarrhea, to fatigue, poor concentration, forgetfulness and headaches, explains Melinda Dennis, M.S., R.D., L.D.N., the nutrition coordinator at the Beth Israel Deaconess Medical Center’s Celiac Center. People with these symptoms may feel better when following a gluten-free diet.

The clincher? People with NCGS do not test positive for celiac disease.

While the first case report on NCGS was documented in 1978, it wasn’t until 2011 that the first well-done clinical trial explored this phenomenon. The double-blind, randomized study published in the American Journal of Gastroenterology included 34 patients who suffered from irritable bowel syndrome (IBS) but didn’t have celiac disease. All study participants were asked to eat a gluten-free diet, and the study then gave each participant a daily muffin and two slices of bread that either did or did not contain gluten. After six weeks, significantly more patients in the gluten group (68 percent) reported worse symptoms of pain, bloating and fatigue than the gluten-free group (40 percent).

So while not all IBS patients benefited from the gluten-free diet, this study and recent trials like it suggest that NCGS does exist and that some patients may benefit from a gluten-free diet.

However, it’s still not clear how many people suffer from NCGS. While it’s thought to be more common than celiac disease—which affects an estimated 1 percent of the world’s population—research suggests NCGS may affect anywhere from less than 1 percent up to 13 percent of the population.

What Causes Gluten Intolerance?
Chickpea Potato Hash

Gluten has to be to blame, right? If only life were that simple.

Even though it is the most recognized culprit, the role of gluten in NCGS is far from definitive. That’s why some experts refer to NCGS as “wheat intolerance syndrome.”

For example, a 2017 analysis published in Clinical Gastroenterology and Hepatology found that, of 231 people presumed to have NCGS, only 38 (16 percent) showed gluten-specific symptoms when “challenged,” or unknowingly given gluten-containing food while following a gluten-free diet.

So what else could it be? There’s some evidence that other proteins, specifically amylase-trypsin inhibitors, are the cause. Like gluten, these proteins aren’t fully broken down during digestion and may cross the intestinal barrier.

Test-tube and mouse studies suggest that these proteins may cause an innate immune response (similar to a reaction to things like insect bites or infections) in some. This is different from the more adaptive response seen in celiac patients. In those people, the body develops an army of immune cells designed to specifically terminate gluten—and keeps that vendetta in its “memory.”

Plus, there’s the issue of FODMAPs, a collective term that includes foods high in fructose (like apples and pears), oligosaccharides (wheat and onions), galacto-oligosaccharides (legumes) and sugar polyols (sorbitol and mannitol). A low-FODMAP diet is usually implemented by practitioners for those suffering from IBS. But many foods that are high in gluten are also high in FODMAPs. That’s why some experts speculate that the improvement of symptoms on a gluten-free diet is wrongly perceived as a result of the reduction in gluten intake. Instead, it may stem from the reduction in certain FODMAPs like the fructose in these foods, explains Dennis.

Who Is at Risk for Gluten Intolerance?
chipotle Chicken Quinoa Burrito Bowl

Apart from having symptoms, there are no clear risk factors for developing NCGS. While celiac disease has a clear genetic link—family members of those with celiac are 5 to 20 percent more likely to develop a gluten disorder than the rest of the population—NCGS does not yet appear to be passed on genetically.

However, one risk factor does seem to be clear. Having an autoimmune disorder like type 1 diabetes may be linked with NCGS, suggests a 2015 study published in Gastroenterology. Forty-two patients with NCGS were followed for three years and, when compared to corresponding patients with celiac disease and IBS, similar numbers of people with NCGS (24 percent) and celiac disease (20 percent) developed autoimmune disorders—much more than those with IBS.

How Do You Diagnose Gluten Intolerance and Treat It?
white bean veggie salad

Unfortunately, there are no diagnostic tests for NCGS. Instead, it is a diagnosis of exclusion.

If someone has symptoms of gluten sensitivity and suspects gluten is an issue, they should see a gastroenterologist who specializes in NCGS so that they can rule out celiac disease and other gastrointestinal disorders before going on a gluten-free diet, instructs Maureen Leonard, M.D., clinical director of the Center for Celiac Research & Treatment at Massachusetts General Hospital.

Common tests to rule out celiac disease include genetic testing—95 percent of people with celiac disease have two copies of a gene called HLA-DQ2—and a blood test called tTG-IgA that checks if your immune system is reacting to gluten. If these tests come back negative and NCGS is suspected, then patients are typically referred to a trained dietitian who can counsel them on the gluten-free diet or help identify any other food sensitivities that could be contributing to symptoms. Because intestinal damage is not involved, some are able to follow a gluten-free diet more loosely while managing their symptoms and improving their quality of life than those with celiac disease, Dennis says.

Living with Gluten Intolerance
Research on gluten intolerance is still in its early phases, but many people with intolerance do find relief after working with a dietitian to rule out foods that exacerbate their symptoms. Thankfully, the impacts of NCGS do not appear to be as extreme as with celiac disease, such as damage to the small intestine. However, the long-term health impacts of living with NCGS are largely unknown.

What experts do know: it’s best not to self-diagnose. Because the gluten-free diet has become so widespread—and is often misunderstood as being inherently healthier—many people self-diagnose as being gluten-intolerant without first ruling out celiac disease. That could be dangerous. Not only can a gluten-free diet be overly restrictive and lacking in several nutrients (including calcium, iron, B vitamins, fiber and vitamin D), untreated celiac disease can result in a higher risk of early death, infertility, growth impairment in children, osteoporosis, liver complications and other health problems. If you’re worried, don’t go it alone. Talk with your doctor about your options.