What is gluten?Gluten is a protein that contains gliadin and is found in certain grains including wheat, barley, and rye. Gluten is a storage protein, also called a prolamin. In fact, all grains have prolamins, the reason we know a lot about gluten is because of it's relationship with celiac disease. When the gliadin found in gluten interacts with the intestinal wall of people with celiac disease, it causes the release of zonulin, a protein that opens up the intestinal wall and allows the contents of the intestine to react with the immune system. This is called intestinal permeability. It does this by dissolving tight junctions between cells that seal the contents of the intestine and prevent it's contents from reacting with the immune system. This is a less than ideal scenario obviously, but should people without celiac disease be concerned?
In addition to celiac disease, there is a condition called non-celiac gluten sensitivity that some people experience. People with non-celiac gluten sensitivity react to gluten, their reaction just isn't quite as severe as people with celiac disease. But how common is this? It's really hard to say. Even for a concrete condition like celiac disease, it's very difficult to diagnose because different people tend to have different symptoms and lab tests are not currently up to snuff. While most people with celiac disease have digestive symptoms, not all do(1). For some people, symptoms can involve rashes and for others symptoms can be neurological. In addition, the symptoms differ for adults and children. Since it is so difficult to categorize the symptoms of celiac disease, the less severe reaction seen in non-celiac gluten sensitivity makes it even more difficult to pin down.
Is gluten sensitivity becoming more common?One of the first things people point out when discussing the rise in celiac disease is that we are simply better at diagnosing it. A study carried out in 2009 showed that the rise isn't simply a matter of better diagnosis. Researchers looked at the blood of Air Force personnel collected from 1948 to 1954 and compared it to the recently collected blood of people from Minnesota of similar age to determine if the prevalence of undiagnosed celiac disease has increased or if the increase was simply due to better diagnosis. The researchers found that the people from Minnesota were more than 4x more likely to have the antibodies associated with celiac disease in their blood than the Air Force personnel(2). This suggests that there is something else at play other than better diagnosis.
How can you go from not reacting to gluten to having a reactionOne of the more frustrating things about gluten sensitivity is that people can eat gluten for many years without having a problem and then all of a sudden begin reacting to it. One thing that gets brought up when people feel they may be reacting negatively to gluten is that the condition is new. How can someone seemingly go from having absolutely no reaction to gluten at all to having one so severe that they can't function normally? The key to gluten sensitivity, celiac or otherwise, may lie with the trillions of bacteria that reside in your gut, and there is ample evidence to suggest so.
Some research points to gluten being a potential problem for most people. Eighty percent of humans produce zonulin and intestinal tissue samples from both celiacs and non-celiacs produce zonulin when treated with gluten(3). The reason people with celiac disease have a more severe reaction than people without celiac disease appears to be because the intestinal permeability related to zonulin lasts much longer in celiacs than non-celiacs. We know that the beneficial bacteria within the gut ferment plant fibers that we can't digest in to short chained fatty acids that repair the tight junctions between cells of the intestinal wall. In people with gut dysboisis, the composition of gut bacteria is changed and can lead to digestive problems and there is evidence that people with celiac disease have gut dysbiosis(4). Perhaps this is one of the reasons that zonulin has a greater effect on people with celiac disease than those without it.
Other factors affecting intestinal wall integrityAside from gluten, there is another trigger that causes zonulin to dissolve the tight junctions between cells of the intestinal wall. When bacteria overgrow from the large intestine in to the small intestine, or when pathogenic bacteria overpopulate and beneficial ones underpopulate, zonulin opens up the tight junctions to pull water in to the intestine to flush the pathogenic bacteria out. A recent article in the NY Times went through quite a bit of the current theories on celiac disease and a change in gut bacteria is right up at the forefront. Not only can it impact a person's ability to re-seal the tight junctions, but it can compound the effect zonulin has on intestinal permeablity.
Zonulin is not the only thing that causes a problem in the intestinal wall, inflammation also causes the integrity of the intestinal barrier to be compromised. Obese people tend to have increased levels of inflammation as well as a population of gut bacteria that make this inflammation worse. They also tend to have higher levels of zonulin circulating in their blood(5). There have been many studies in mice showing that simply giving the bacteria of lean mice to obese mice not only made the obese mice lean, it also decreased systemic inflammation. This effect is also dependent on diet(6). Obese mice who eat a diet low in vegetable fiber don't get the benefits from ingesting the bacteria from the lean mice. In the future, fecal transplants may be capable of putting a person with celiac disease in to remission, allowing them to eat wheat with no problem, but we aren't there yet and it would still require a change in diet. Of the factors that a person can manipulate, diet is currently the best option.
What to be on the lookout forAs mentioned above, a diet low in soluble fiber from fruits and vegetables can cause gut dysbiosis over a long period of time. Frequent use of antibiotics, currently or in the past, also can have an affect. In addition, other factors out of your control can increase your likelihood of becoming sensitive to gluten through changes in gut bacteria. Being born by C-section and not being breastfed increase a person's likelihood of gut dysbiosis later in life, so people who satisfy either or both conditions should be vigilant and consume a diet high in vegetables. In addition, if your mother was obese she could have passed on her less than ideal gut bacteria to you in the event you were born vaginally.
Other conditions associated with intestinal permeability and, therefore, linked to gluten sensitivity include most autoimmune diseases including asthma, rheumatoid arthritis, Type 1 diabetes, Lupus, seasonal allergies, and multiple sclerosis. It is theorized that one of the conditions underlying all autoimmune diseases is intestinal permeability so removing gluten is prudent if you have one of these conditions. In addition to autoimmune disorders, people with irritable bowel syndrome/disorders should also avoid gluten due to high levels of intestinal inflammation and potential gut dysbiosis.
Type 2 diabetes and obesity are associated with higher levels of inflammation and zonulin and could also be related to gluten sensitivity. Since zonulin also regulates the tight junctions of the blood brain barrier and the lungs(7), people with a family history of Alzheimer's disease or who have frequent respiratory infections should probably limit their exposure to gluten. Finally, high stress levels as well as increased age are related to changes in both gut bacteria as well as immune system function and may impact a person's sensitivity to gluten. A recent study showed smoking cessation can lead to the same changes in gut bacteria that is associated with obesity(8), so if you plan on quitting smoking it may be a good idea to limit gluten exposure during this time,
While this is certainly quite a list of possible issues that gluten sensitivity can contribute to, the treatment is the same: Remove gluten and consume more vegetables. Note that the solution isn't to start consuming gluten free snacks, as they will only contribute to gut dysbiosis by not providing soluble fibes for the good bacteria in your gut to ferment. While probiotics are also an attractive option, there is no point in taking them unless you are eating foods that will support their proliferation in your gut. In time, I believe quite a few people who are sensitive to gluten can tolerate it once they re-establish the proper balance of bacteria in their gut. For some people this will be easier than others depending on which other foods they are sensitive to and how much damage they have caused.