Elena Verdú is a professor at McMaster University (Canada) and a member of the GMFH Board of Experts. She runs the Verdu Lab, where her team investigates host-microbial and dietary interactions in the gastrointestinal tract as they relate to the pathogenesis of celiac disease and inflammatory bowel diseases (IBD).
What is celiac disease?
EV: It is a common food sensitivity that affects people with certain genes when they consume a common group of proteins, which are called gluten, and that are present in cereals like wheat, rye and barley.
People who suffer from celiac disease experience severe gastrointestinal symptoms, like diarrhea, bloating, abdominal pain. Or they can also have extraintestinal symptoms, such as anemia or bone loss, frequent fractures. And they can also be mildly symptomatic, which is why sometimes it is very difficult to diagnose celiac disease and a great majority of these patients are undiagnosed.
We diagnose celiac disease by a blood sample and a blood test and then the diagnosis is usually confirmed by a small piece of tissue, which we call biopsy, that we take from the small intestine during an endoscopy. And once the diagnosis is confirmed, it is very, very important for patients with celiac disease to follow a strict gluten-free diet through life.
Why is it important to adhere to a gluten-free diet?
EV: As I mentioned, gluten proteins are the drivers or the triggers of inflammation in celiac disease. And it is this inflammation that damages the lining of the small intestine and leads to symptoms and to the nutritional deficiencies and complications of the disease.
Patients with celiac disease are very sensitive to very small amounts of gluten. And therefore, it is of utmost importance that when a proper diagnosis is made, these patients follow strict gluten avoidance. And this needs to be performed with the help of health professionals, because a gluten-free diet not properly done could lead to complications.
What is the role of the gut microbiota in all of this?
EV: Well, we know that for someone to suffer from celiac disease, we have to have the right genes and that person has to consume gluten. However, not everyone consuming gluten and having the right genes will develop celiac disease. That is why we believe that there are cofactors that are important to lead a person to suffer from celiac disease. And one of these cofactors can be the gut microbiota.
So, there are some studies that showed differences in the microbial composition of the gut in patients with celiac disease compared with individuals that do not have celiac disease. And more importantly, there are studies that show that gut microbes in patients with celiac disease metabolize or digest gluten in a different manner, in a way that can lead to having a higher susceptibility to the disease.
Moreover, there are also studies showing that gut microbes can even digest other important food components not related to gluten, like essential amino acids like tryptophan, which are important in producing metabolites that can be protective of the gut lining. And patients with celiac disease can have alterations in this type of metabolism, as well.
Last but not least, there are studies showing that immune cells in patients with celiac disease can cross-react and recognize certain portions of microbes or opportunistic pathogens present in the small intestine of patients with celiac disease and cross-react with gluten sequences.
So overall, gut microbes could be, depending on the activity and the type of microbes that a patient or an individual harbors in the GI tract, a cofactor that can lead to more susceptibility or less susceptibility to develop celiac disease. But of course, we always have to have the right genes and the exposure to gluten as well.
What is your opinion about the trend of people who have not been diagnosed as celiac following a gluten-free diet?
EV: The only medical indication that is evidence based for following a gluten-free diet, strict and for life, is to have a proper diagnosis of celiac disease. Celiac disease is not a fashion. Celiac disease is a severe condition with an autoimmune background.
Autoimmune means that the immune system is attacking our own organs, and in the case of celiac disease, this is the lining of the small intestine.
In the case of individuals who do not have celiac disease and in whom celiac disease has been ruled out properly, if those patients believe or feel that a wheat-containing diet causes symptoms, then this can be discussed with their health professional, and then a lower gluten-containing diet may be a possibility. But this always needs to be followed up by a healthcare professional, because a gluten-free diet which is not supervised can lead to nutritional deficiencies and other complications.