By Meryl Ong
For more articles on lifestyle medicine, please visit Meryl's blog: The Mindful Hustle
The gluten-free diet is often passed off by laymen as just another fad diet—similar to the Cabbage Soup Diet of the early 1980s or Paleo Diet in the 2010s. While this may be all that is of interest to a health-conscious individual in search of a novel ‘solution’ to shred off a few pounds*, the gluten-free diet astonishingly serves as the sole treatment method for a medical condition known as Coeliac disease. As of 2018, this medical condition has been deemed by scientists to be “a major public health problem worldwide,”with the UK and Europe seeing every 1 in 100 people affected. (*Adhering to a gluten-free diet does not necessarily lead to weight loss. There have also been many cases showing otherwise. You can read more about it here. Although this diet has been claimed by many to confer health benefits and contribute towards a rise in energy levels, more research is needed to back these assertions.)
What is Coeliac disease? Coeliac disease is classified as an autoimmune disease, a condition where the body’s immune system attacks healthy and normal cells because of its inability to distinguish between self and foreign cells. More specifically, the consumption of gluten by a patient with coeliac disease is responsible for triggering an autoimmune response. Gluten is a dietary protein found in wheat, barley and rye. It contains specific substances which unintentionally induce bodily defence reactions in certain individuals, resulting in damage to the small intestine (small intestinal mucosal injury) and ultimately results in a reduced ability of patients to absorb nutrients from food (nutrient malabsorption).
Individuals most at risk of developing Coeliac disease are those with: 1. A family history of the condition (particularly so if a parent or sibling is affected) 2. Autoimmune disease-causing genes 3. Pre-existing medical conditions such as Type 1 diabetes, hypothyroidism, Turner’s syndrome and Down syndrome.
Patients with coeliac disease often have variable clinical presentations, including diarrhoea, fatigue, weight loss, bloating, abdominal pain, nausea and vomiting as well as constipation. Furthermore, children who have been diagnosed are more susceptible to digestive complications compared to adults. Despite our knowledge of the symptoms of coeliac disease, only a third of people with this condition have been clinically diagnosed. In fact, the average length of time required to diagnose coeliac disease despite the early presentation of symptoms is a whopping 13 years. Late diagnosis of coeliac disease is largely due to misdiagnosis, as the symptoms of this illness are similar to that of other digestive medical conditions, like Irritable Bowel Syndrome (IBS). Furthermore, since damage to the small intestines is a slow and gradual process, the onset of gastrointestinal symptoms is often delayed. Pathophysiology of Coeliac disease So, what happens when an individual with Coeliac disease consumes a meal containing gluten? (Let’s assume a bagel made of wheat flour.)
Photo credits: Medscape on YouTube
- Gluten in the bagel is broken down into a type of protein known as gliadin, which is resistant to degradation. - Once gliadin reaches the lumen of the small intestine, it binds to secretory Immunoglobin A (IgA), an antibody involved in immune action along mucous membranes and protects enterocytes (cells of intestinal lining) against pathogens and toxins. - Under normal circumstances, anything bound to secretory IgA tends to get destroyed by the body’s defence mechanism. This, however, is not the case in patients with coeliac disease. Instead, the gliadin-IgA complex becomes attached to a receptor called TFR which is typically involved in the absorption of iron. - After binding to TFR, gliadin is transported across the enterocyte into the lamina propria (thin lining of the intestinal wall). - An amide group is removed from gliadin by tissue transglutaminase (tTG) to form deamidated gliadin. - Deamidated gliadin is then engulfed by a macrophage (type of phagocyte), and these macrophages present gliadin proteins on the surface of its cell. - The structures which hold up the proteins and allow macrophages to present them to their extracellular environments are known as Major Histocompatibility Complexes (MHC II), and each one is specific to the molecules it can present. Since these MHC II are encoded for by HLA genes, it is useful to note that patients with coeliac disease have been found to possess the genes HLA-DQ2 and HLA-DQ8, allowing deamidated gliadin proteins (specifically) to be displayed on the cell surface.
Photo credits: Medscape on YouTube
- T-lymphocytes then recognise and bind to the presented gliadin proteins, stimulating the release of inflammatory cytokines which in turn cause damage to the intestinal epithelial cells. - T-lymphocytes also activate B-lymphocytes, which produce a range of antibodies. - Finally, T-lymphocytes also trigger the action of Killer CD8+ T cells, which damage inflamed cells—causing further damage to the epithelial cells. - Since destruction of the epithelial lining can be severe, it is likely that more gliadin proteins can cross the membrane, resulting in positive feedback. Therefore, Coeliac disease ultimately results in enterocyte damage (destruction of the cells of the intestinal lining) as well as villous atrophy (erosion of intestinal villi).
Photo credits: The Celiac Scene
Most noticeably, coeliac disease results in the flattening of villi while crypt cells (stem cells for regeneration of intestinal epithelium) lengthen. If left untreated or undiagnosed, a common long-term complication faced by patients with coeliac disease is nutrient malabsorption. This is where important nutrients, vitamins and minerals are not absorbed effectively by the body, which can lead to conditions such as osteoporosis and various types of deficiency anaemia (including iron, vitamin B12 and folate deficiency anaemia). Malnutrition can also compromise the body’s ability to recover from injuries and fight off infections.
How is Coeliac disease diagnosed? There are a few methods physicians use to determine whether a patient has Coeliac disease. Doctors often use a combination of these tests to aid them in their diagnosis. 1. Self-checks: Doctors may encourage patients to adopt a gluten-free meal plan to determine if their symptoms are relieved as a result. However, this method is non-exhaustive and further diagnostic tests are conducted in most cases to complement this piece of evidence. 2. Celiac blood test (tTG-IgA test): This helps to identify specific antibodies in blood (known as tissue transglutaminase IgA) associated with the autoimmune reaction against gluten. It is possible to obtain false-negative blood test results though, especially if patients have IgA deficiency. A separate blood test can help to identify such cases. 3. Genetic testing: Drawing of blood or swabbing of the mouth (but again, this is non-exhaustive). 4. Endoscopy: A small camera is manoeuvred down the alimentary canal into the small intestines. The doctor will then determine if there are signs of villous atrophy. 5. Small intestine biopsy: The doctor takes a few samples from the small intestine and observes them under a microscope. If there is perceived damage to the intestines, a diagnosis of coeliac disease can be made. Interestingly, a patient producing both a positive blood test and presenting with a skin rash (known as dermatitis herpetiformis) can immediately be diagnosed with coeliac disease—the high degree of confidence in this diagnosis has been backed by robust scientific research. Even so, this deduction can be ascertained by conducting a skin biopsy, which should indicate the presence of anti-gluten antibodies under the skin. Treatment of Coeliac disease The only treatment option available to patients with coeliac disease is following a gluten-free diet, which should aid with managing symptoms and preventing the development of more severe, long-term complications. Coeliac disease is a lifetime disease with no cure. This implies that individuals with coeliac disease have to adhere to a strict gluten-free diet for a lifetime, which can be a daunting and inconvenient lifestyle change for those newly diagnosed.
What does a gluten-free diet entail?
Simply put, a gluten-free diet is a meal plan that excludes any foods containing gluten—automatically removing wheat, barley and rye from the list of grains safe for consumption. Widely consumed foods such as bread, cereals, pasta, sausages, fish fingers and a range of sauces are among those which should be avoided. Patients are encouraged to be cautious about their food selections and diligently identify allergens on food labels. Accidental consumption of gluten may result in the onset of symptoms like diarrhoea and vomiting which can last for several days. On a more optimistic note, fruits and vegetables, beans, legumes, nuts, eggs and a variety of meats can still be incorporated into the diets of patients. Alternatives for grains are still plenty, including corn, quinoa, rice and buckwheat. For those of you who are keen to find out more about the gluten-free diet, you will find a more comprehensive description here.
I hope this article has enabled you to appreciate the clinical reasons behind the gluten-free diet, rather than simply viewing it through the lens of a consumer presented with ‘yet another dietary option’. It is important to recognise that not everyone gets to experience and enjoy the same level of freedom when making food choices. There are resilient individuals among us who have to make seemingly small yet significant decisions every single day to live fully and healthily, and I believe they are more than deserving of our support and encouragement. Taking the time to educate ourselves on what others have to experience daily and choosing to be empathetic towards them can only bring us one step closer to becoming a more inclusive society where everyone feels seen, heard and cared for.
*Please note that this article should not be perceived as medical advice, diagnosis or treatment under any circumstance. Please seek advice from a qualified healthcare professional should you have any questions about a medical condition.
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