Lately, there has been a lot of press about gluten, which is a wheat protein. To look at the proliferation of gluten-free products on the supermarket shelves, one would think that half the country has problems with gluten. Is this a real issue, or the latest fad? How many of us really need to avoid gluten? What is celiac disease? Is there such a thing as non-celiac gluten intolerance? Should people without any of those problems avoid wheat products? At least once a week, I see a patient who wants to know if they could have celiac disease, or possibly gluten intolerance. Often, they have put themselves on a gluten free diet. They may feel better (or not) and want to know whether they should continue the diet.
Celiac disease is a true gluten allergy, where ingestion of gluten leads to changes in the lining of the small intestine, which in turn leads to difficulty absorbing nutrients. We used to think that celiac disease is primarily a disease of children, but now we know that it can occur at any age. It can occur through all ethnic groups as well, and is said to be present in .6-1% of the world’s population. It is more common in people who have a sibling, parent, child with celiac disease, with estimates ranging from 5-20% in those groups. Symptoms can range from no symptoms to bloating, abdominal pain, weight loss, and diarrhea, or to symptoms more commonly thought of as irritable bowel symptoms such as gas, constipation, or alternating bowel habits. There may be more generalized symptoms such as fatigue, headaches, rashes, joint pains, or findings such as anemia or abnormal liver tests.
The treatment of celiac disease involves avoiding eating foods that contain gluten. Gluten is a wheat protein found in products made with wheat, rye or barley, such as bread, pasta, cereals and baked goods and as an additive in many foods, medications and even makeup. The diet must be maintained throughout one’s life. Possible complications of untreated celiac disease include osteoporosis, neurologic problems, fertility issues, lymphoma and cancer of the small bowel, so even if patients do not have symptoms, it is important for them to be treated. People without symptoms may be diagnosed because they are relatives of a person with celiac disease, or because they have abnormal blood tests such as low blood counts or low iron or abnormal liver enzymes.
Celiac disease is diagnosed by a blood test, and by a biopsy of the small intestine, taken through an endoscope. If the blood test is abnormal, response of celiac disease to diet can be followed by re-checking the blood test. An endoscopy (evaluation of the upper part of the intestinal tract) may be performed periodically to monitor the lining of the small intestine.
Gluten sensitivity or non-celiac wheat sensitivity is less well defined. There is no specific blood test or biopsy that can make that diagnosis. The symptoms that have been attributed to gluten sensitivity are the same as those caused by celiac disease. Of note are the above mentioned symptoms and headache, depression, numbness of extremities, moodiness, muscle or joint pain, change in menstrual pattern, weight gain. By definition, patients with non-celiac gluten sensitivity do not have abnormal blood tests or tissue biopsies. They report feeling better when they avoid gluten and report recurrence of symptoms with ingestion of wheat products. The best test for non-gluten celiac sensitivity would be for patients to go off gluten and see if their symptoms resolve. They then would go back on either a gluten-containing pill or a placebo and see if symptoms recur. This has been used in studies of people with gluten sensitivity but is not available to the general public.
One cannot be tested for celiac disease when following a gluten-free diet. It makes the tests inaccurate. Therefore, when possible, patients should at least undergo blood testing for celiac disease prior to initiating a gluten-free diet. Many patients come to me already on a gluten free diet. If they are unwilling to resume eating gluten in order to be tested for celiac disease, we can perform HLA genotyping testing (a blood test). Two HLA types (similar to blood types) are associated with celiac disease, HLA-DQ2 and HLA DQ8). If a patient has one of those HLA types, it does not mean that they have celiac disease, but if they DON’T have that HLA type, they are very unlikely to have celiac disease. The differentiation between gluten intolerance and celiac disease is important because, gluten intolerance does not cause long term complications.
It is difficult to know how many people who put themselves on a gluten free diet have gluten sensitivity. A small percent of them have wheat allergy. Some may have irritable bowel syndrome or may have other food sensitivities. Why would a patient with IBS respond to a gluten-free diet? One may be that they were previously eating a diet high in processed foods or too much grain fiber, causing gas and bloating. They could have been eating too much “junk food” with either fat or sugar or both (i.e. in cake) leading to symptoms. Eating gluten free makes a person more aware of what he or she is eating and also requires planning. The placebo effect is very strong in many aspects of medicine and gastrointestinal symptoms are no exception. Although a gluten free diet is not necessarily a healthier diet, it is not harmful; therefore, if people feel better avoiding gluten, there is no reason to resume eating wheat products. People with gluten sensitivity rather than celiac disease may be able to ingest small amounts of gluten without symptoms.
There is no evidence that a gluten free diet is healthier than a regular diet. In fact, there are lots of snack foods now labelled gluten free. For patients who have neither celiac disease nor gluten intolerance, I recommend a balanced diet with minimal processed foods. For those who need to follow a gluten free diet, I also recommend minimizing processed foods and eating carbohydrates that are naturally gluten free, such as rice and potatoes.
Fasano, A. and Catassi, C. Celiac Disease. New England Journal of Medicine 2012;367:1731-43