Gluten is a protein naturally found in cereals such as wheat, barley, and rye. Harmless for most of us, gluten can cause quite a lot of headache (and bellyaches, among other things) for certain people. Today, we’ll take a look at the different kinds of gluten intolerance and the symptoms they can cause.

Gluten makes dough elastic, knead-able, and bouncy. You can see how it works in this cake, keeping those stringy bits in the middle from breaking.
Image credits Andreas Lischka.

Wheat (genus Triticum) makes the world go round. Not literally, but it does play a big role in keeping us humans fueled up. It was one of the first domesticated food crops, and for roughly 8 millennia now, wheat has been the staple food of major civilizations in Europe, North Africa, and West Asia. More land area is dedicated to growing wheat than any other commercial crop on Earth, and global production of wheat outstrips that of any other crop — including rice, maize, and potatoes.

Barley (Hordeum vulgare) is another long-time companion of human farmers. First cultivated around 10,000 years ago, it was the fourth most-produced grain in the world in 2016, although output has somewhat declined since then. Barley is very useful as an animal feed but is perhaps most celebrated for its role in beer and distilled beverage production.

Both of these cereals, along with rye, their related species, and various hybrids, are part of the grass (Poacea) family of plants. Altogether, they supply a huge part of the calories and nutrients consumed by us and our livestock. They also supply the majority of raw materials used in producing alcohol.

Apart from their economic importance, these crops are also notable for their high content of gluten and gluten-like proteins. This is a bit of a bummer for around 1.5% to 14% of the world’s population, who have to contend with various forms of gluten intolerance.

What is gluten intolerance

Gluten intolerance is a somewhat-umbrella term that refers to adverse reactions to gluten. I say ‘somewhat-umbrella’ because it tends to be improperly applied to several conditions that — while similar in effects — are different in origin. These include celiac disease (CD), non-celiac gluten sensitivity (NCGS), wheat allergy, dermatitis herpetiformis, and (more rarely) gluten ataxia.

The most extreme form of gluten intolerance is celiac disease (also known as gluten-sensitive enteropathy, sprue, or coeliac). Roughly 1 in 100 Americans contend with CD, and this percentage seems to hold true for the rest of the world as well. CD is basically an autoimmune disorder. The body of a CD patient reacts with extreme violence to the presence of gluten in one’s food — to the point where their immune system will attack the inner lining of the small intestine to ‘protect it’ from gluten. Such offensives cause immediate symptoms for the patient. If exposure to gluten is maintained over a longer period of time, sustained damage to the gut’s lining leads to problems in absorbing nutrients (malabsorption).

High-magnification image of intestinal lining damaged by celiac disease.
Image credits Nephron / Wikimedia.

Non-celiac gluten sensitivity is more controversial. We don’t know, really, what causes this condition (or if it’s even an actual thing). Our best guess is that it has something to do with gluten-associated proteins and/or other chemical compounds present in gluten-containing crops. Since we don’t know what causes it and how, NCGS is generally diagnosed by eliminating other possibilities (namely CD and wheat allergies). Roughly 0.5% to 13% of the world’s population has NCGS. While its exact symptoms are debated, NCGS seems to share most gastrointestinal symptoms of CD, wheat allergies, and irritable bowel syndrome, but with a different interval between exposure and onset of symptoms. NCGS also seems to entail a host of extraintestinal (not related to the gut) symptoms that CD lacks.

Wheat allergy is your run-of-the-mill allergy, but rather misleadingly-named. Like other allergies, it can manifest as a food- or contact-allergy. Unlike other allergies, it can be caused by a range of compounds (rather than a particular allergen) contained in wheat. The European Center for Allergy Research Foundation (ECARF) states that “wheat allergy generally appears in infancy,” noting that roughly 0.3% of European children under the age of 5 and around 0.1% of all Europeans are allergic to wheat, making it a relatively rare condition.

Dermatitis herpetiformis (DH), or Duhring-Brocq disease, is a tell-tale sign of celiac disease, although the exact mechanism by which one causes the other remains unknown. The condition is a skin inflammation characterized by chronic rashes on the skin with red, liquid-filled blisters. They’re also very itchy. Estimates of DH prevalence range from 10 in 100,000 to around 80 in 10,000 individuals.

Gluten ataxia is a proposed condition. It’s basically gluten-induced ataxia, a condition characterized by dysfunctions in the central nervous system leading to loss of voluntary control or coordination over muscle movements. Gluten ataxia “usually presents with gait and lower limb ataxia” and may account for “15% amongst all [cases of] ataxias and 40% of all idiopathic sporadic ataxias,” according to a study published in 2015.

It’s important to note that there are several varieties of gluten intolerance going forward. Each has its own particularities of symptoms. However, there are some general symptoms that are indicative of such disorders.

Symptoms of gluten intolerance

Most of them have to do with your belly. But not all of them.
Image credits Darko Djurin.

Abdominal pain after ingesting gluten — from grains and derived products such as flours, bread, baked goods, or beer — is the most common symptom of gluten intolerance at large. Up to 83% of those with gluten intolerance experience abdominal pain and discomfort after eating gluten.

Abdominal bloating is a close second. It’s a sensation of ‘swollenness’ or ‘fullness’ in one’s belly, caused by the release of gases in the gut. Generally uncomfortable, abdominal bloating can become painful and/or cause shortness of breath. Around 87% of people suspected to have NCGS experience bloating, but a majority of CD patients also report this symptom.

Bowel inflammation after consuming gluten is a common symptom of celiac disease. Damage of the gut lining causes inflammation resulting in significant digestive discomfort. In the long run, it can also lead to poor nutrient absorption.

Over 50% of gluten-sensitive individuals (both CD and NCGS) regularly experience digestive symptoms such as diarrhea, while about 25% experience constipation. Patients also report alternating between the two states. Celiac disease patients may also experience pale and foul-smelling feces (due to nutrients left over in the stool).

Tiredness after consuming gluten can also be a symptom. This is a bit trickier to diagnose, as life by itself tends to be quite tiresome. However, if you regularly (or constantly) feel fatigue and tiredness, especially after eating foods that contain gluten, it could be indicative of underlying gluten intolerance. Around 60% to 82% of gluten-intolerant individuals commonly experience tiredness and fatigue. Gluten intolerance can also cause iron-deficiency anemia, which in turn will make you feel tired and spent overall.

Dermatitis herpetiformis, as we’ve seen above, is a pretty dead giveaway for celiac disease. Other skin conditions — psoriasis, alopecia areata, and chronic urticaria — have also shown improvement under gluten-free diets, which suggests a link between them and gluten intolerance.

Gluten intolerance may also predispose individuals to depression and anxiety, especially those suffering from CD. While the mechanism underlying this link remains unknown, it has been proposed that changes in gut flora and exorphins formed during gluten digestion may interfere with serotonin levels in the brain. It also seems that switching to a gluten-free diet makes some patients “feel better” even if their gastrointestinal symptoms persist; all of which suggests a link between the two.

What to do about it

TL;DR don’t put these things in your mouth.
Image credits National Cancer Institute / National Institutes of Health.

The best course of action is to go talk to a doctor. But there are some preventive measures you can take if you think you’re suffering from gluten intolerance.

Unsurprisingly, you should avoid items that contain gluten — wheat, barley, malt, rye, and their derived products (brewer’s yeast can also contain gluten, for example). Some common foods and drinks that contain gluten include:

• pasta, noodles
• bread, pastries, baked goods such as crackers, biscuits, and cakes
• breakfast cereals
• pancakes, waffles, crepes
• many sauces and gravies use flour-derived gluten as thickening agents
• beers, malt beverages
• potatoes, maize, and rice can also become contaminated with gluten in facilities that also process gluten-rich grains

Gluten-free varieties of such items are commercially available, although they tend to be more pricey. So it’s possible to enjoy them without worrying about gluten. But, as a rule of thumb, if you suspect a food item contains or has been in contact with wheat, barley, rye, malt, or products derived from those (and you believe you might be suffering from gluten intolerance), don’t eat it.

Now, I think it’s important to note that there’s also somewhat of a witch hunt among fad diets regarding gluten. Many such diets suggest gluten itself is bad for your health even if you’re not gluten-intolerant. There’s no credible scientific evidence for such claims that I could find, so I’m comfortable calling it a myth. Another part of the issue is that the symptoms of gluten intolerance are widespread and can have a lot of different potential causes — which makes gluten intolerance easy to misdiagnose.

All in all, if you believe you might be suffering from gluten intolerance, the best course of action is to go talk to a doctor.

On oats

In response to numerous queries concerning the use of oats in various products, the North American Society for the Study of Celiac Disease (NASSCD) released a statement saying that “the use of oats uncontaminated by wheat, barley or rye by individuals with celiac disease and dermatitis herpetiformis in North America has been endorsed by most experts.” However, they also note that “regular (commodity) oats in North America are likely to be contaminated with wheat and barley,” and recommend consulting a doctor or dietitian before including oats in gluten-free diets, as well as monitoring after inclusion.

There is some evidence that avenin, an oat protein similar in form and function to gluten, “can activate gluten-reactive T cells”, the Celiac Disease Foundation reports citing a 2015 study. A different study, published in 2017, reported that avenin “can cause small bowel mucosal damage in some people with coeliac disease.” While the first paper concludes that “low-level oats consumption may be insufficient for clinical relapse in CD patients,” the second one does not recommend including this cereal in gluten-free diets.

It has to be noted, however, that the second study was performed in Australia, and differences in labeling requirements may confuse results to an extent. The NASSCD, for example, specifies that “oats used in labeled gluten-free foods may now include mechanically/optically-sorted oats, a process which separates oats from wheat, barley and rye by color, size, and shape. These methods are used to produce “clean” gluten-free oats.” The first study also suggests that certain types of oats may induce CD symptoms in patients while others do not.

“Inclusion of oats in a gluten-free diet might be valuable due to their nutritional and health benefits, and several countries currently permit oats to be included as an ingredient in such diets,” it explains.

“However, it is extremely important to remember that in vitro studies have shown that the immunogenicity of oats varies depending on the cultivar used. Future clinical studies should be directed to the development of clinical trials with varieties previously identified as safe by reliable in vitro methods”

If you’re intolerant to gluten, play it safe. Look for the “gluten-free” label, or talk to a doctor to decide if oats are right for you.