- Email: [email protected]
Gluten: going against the grain?
Editorial
Recent years have seen several fad diets come and go, from the rise of Atkins in 2003 to the more recent paleo trend, but gluten-free foods have experienced unprecedented longevity, winning over clean-eating enthusiasts and celebrity endorsements far beyond those who have coeliac disease or wheat allergies. While the incidence of coeliac disease is on the rise (in large part due to increased diagnosis), the popularity of a gluten-free diet has grown disproportionately. One in ten UK households have at least one supposedly gluten-intolerant member, and almost a third of Americans are trying to cut gluten out of their diets. Indeed, gluten-free products have become a multibillion dollar industry, with worldwide sales of gluten-free products estimated to reach as much as US$7·59 billion by 2020. Gluten has been held responsible for a vast range of health problems, from obesity to dementia, as well as a general lack of wellbeing. However, there is a tangible difference between the visible intestinal damage seen in those with diagnosed coeliac disease, for whom a life-long gluten-free diet is a necessity, and the supposed ill effects of gluten in the general population. In people with coeliac disease, an autoimmune response to gluten leads to villous atrophy, resulting in malabsorption, which can cause abdominal pain, weight loss, and malnutrition. Diagnosis requires a blood test and endoscopy, and although about 1% of people are thought to have coeliac disease, only about one in 800 have been diagnosed. This creates a problematic paradox of under-diagnosis while many unaffected people eliminate gluten from their diets in pursuit of unclear health benefits. In addition to coeliac disease, less than 1% of the population have wheat allergy, or other rarer autoimmune reactions. Still an increasing number of individuals report experiencing symptoms when consuming wheat or gluten-containing foods, when coeliac disease and wheat allergy have been ruled out. Self-reported by 0·5–6% of the population in Europe, non-coeliac gluten sensitivity (NCGS; also known as non-coeliac wheat sensitivity or “coeliac-lite”) has had a controversial history. People with NCGS report gastrointestinal and extraintestinal symptoms—including mental confusion, depression, and fatigue—which abate on adoption of a gluten-free diet. Although first reported in the 1970s, its pathophysiology has historically been little understood, and it has been www.thelancet.com/gastrohep Vol 1 October 2016
met with the scepticism of those who question its very existence—particularly in the face of a seemingly faddy dietary trend. The controversy is compounded by self-diagnosis and overlap with functional gastrointestinal disorders like irritable bowel syndrome (IBS). However, a recent study suggests there is more than a grain of truth to NCGS. Melanie Uhde and colleagues reported systemic immune activation, including raised serum concentrations of soluble CD14, LPS-binding protein, and antibodies to flagellin, in individuals reporting sensitivity to wheat but in whom coeliac disease and wheat allergy had been ruled out. The researchers also reported elevation of a marker of intestinal epithelial cell damage, similar to that seen in coeliac disease, implying that sensitivity to wheat could be caused by a weakened intestinal barrier, triggering an inflammatory immune response. These findings could mark the first step towards identification of objective diagnostic markers for NCGS. Nevertheless, we must be clear in the message that there is nothing inherently healthier about a gluten-free diet in those without symptoms. While eliminating gluten could coincidentally increase consumption of fruit and vegetables, and reduce intake of refined carbohydrates such as white bread and pizza, many gluten-free products are deficient in vitamins and nutrients, including B vitamins, iron, and folate, as well as fibre; are heavily processed; and contain large amounts of fat and sugar. Moreover, for patients who believe they have gluten-related symptoms, embarking on a self-imposed gluten-free diet before medical evaluation can result in a missed diagnosis of coeliac disease—meaning that patients actively seeking to improve their health unwittingly miss out on crucial advice about complications, risk to family members, and diet. Furthermore, the ongoing debate regarding the reality of NCGS is counter-productive and fails to prioritise the concerns of patients who experience very real symptoms. These patients are likely to comprise a heterogeneous group, perhaps overlapping with IBS and coeliac disease. Although recent studies have sown the first seeds, more research is needed to establish risk factors, biomarkers, and definitive diagnostic criteria before patients will truly be able to reap the rewards. ■ The Lancet Gastroenterology & Hepatology
Gustoimages/Science Photo Library
Gluten: going against the grain?
For more on sales of gluten-free products see http://www. marketsandmarkets.com/ Market-Reports/gluten-freeproducts-market-738.html For the study by Uhde and colleagues see Gut 2016; published online July 25. DOI:10.1136/gutjnl-2016-311964
85
Recent years have seen several fad diets come and go, from the rise of Atkins in 2003 to the more recent paleo trend, but gluten-free foods have experienced unprecedented longevity, winning over clean-eating enthusiasts and celebrity endorsements far beyond those who have coeliac disease or wheat allergies. While the incidence of coeliac disease is on the rise (in large part due to increased diagnosis), the popularity of a gluten-free diet has grown disproportionately. One in ten UK households have at least one supposedly gluten-intolerant member, and almost a third of Americans are trying to cut gluten out of their diets. Indeed, gluten-free products have become a multibillion dollar industry, with worldwide sales of gluten-free products estimated to reach as much as US$7·59 billion by 2020. Gluten has been held responsible for a vast range of health problems, from obesity to dementia, as well as a general lack of wellbeing. However, there is a tangible difference between the visible intestinal damage seen in those with diagnosed coeliac disease, for whom a life-long gluten-free diet is a necessity, and the supposed ill effects of gluten in the general population. In people with coeliac disease, an autoimmune response to gluten leads to villous atrophy, resulting in malabsorption, which can cause abdominal pain, weight loss, and malnutrition. Diagnosis requires a blood test and endoscopy, and although about 1% of people are thought to have coeliac disease, only about one in 800 have been diagnosed. This creates a problematic paradox of under-diagnosis while many unaffected people eliminate gluten from their diets in pursuit of unclear health benefits. In addition to coeliac disease, less than 1% of the population have wheat allergy, or other rarer autoimmune reactions. Still an increasing number of individuals report experiencing symptoms when consuming wheat or gluten-containing foods, when coeliac disease and wheat allergy have been ruled out. Self-reported by 0·5–6% of the population in Europe, non-coeliac gluten sensitivity (NCGS; also known as non-coeliac wheat sensitivity or “coeliac-lite”) has had a controversial history. People with NCGS report gastrointestinal and extraintestinal symptoms—including mental confusion, depression, and fatigue—which abate on adoption of a gluten-free diet. Although first reported in the 1970s, its pathophysiology has historically been little understood, and it has been www.thelancet.com/gastrohep Vol 1 October 2016
met with the scepticism of those who question its very existence—particularly in the face of a seemingly faddy dietary trend. The controversy is compounded by self-diagnosis and overlap with functional gastrointestinal disorders like irritable bowel syndrome (IBS). However, a recent study suggests there is more than a grain of truth to NCGS. Melanie Uhde and colleagues reported systemic immune activation, including raised serum concentrations of soluble CD14, LPS-binding protein, and antibodies to flagellin, in individuals reporting sensitivity to wheat but in whom coeliac disease and wheat allergy had been ruled out. The researchers also reported elevation of a marker of intestinal epithelial cell damage, similar to that seen in coeliac disease, implying that sensitivity to wheat could be caused by a weakened intestinal barrier, triggering an inflammatory immune response. These findings could mark the first step towards identification of objective diagnostic markers for NCGS. Nevertheless, we must be clear in the message that there is nothing inherently healthier about a gluten-free diet in those without symptoms. While eliminating gluten could coincidentally increase consumption of fruit and vegetables, and reduce intake of refined carbohydrates such as white bread and pizza, many gluten-free products are deficient in vitamins and nutrients, including B vitamins, iron, and folate, as well as fibre; are heavily processed; and contain large amounts of fat and sugar. Moreover, for patients who believe they have gluten-related symptoms, embarking on a self-imposed gluten-free diet before medical evaluation can result in a missed diagnosis of coeliac disease—meaning that patients actively seeking to improve their health unwittingly miss out on crucial advice about complications, risk to family members, and diet. Furthermore, the ongoing debate regarding the reality of NCGS is counter-productive and fails to prioritise the concerns of patients who experience very real symptoms. These patients are likely to comprise a heterogeneous group, perhaps overlapping with IBS and coeliac disease. Although recent studies have sown the first seeds, more research is needed to establish risk factors, biomarkers, and definitive diagnostic criteria before patients will truly be able to reap the rewards. ■ The Lancet Gastroenterology & Hepatology
Gustoimages/Science Photo Library
Gluten: going against the grain?
For more on sales of gluten-free products see http://www. marketsandmarkets.com/ Market-Reports/gluten-freeproducts-market-738.html For the study by Uhde and colleagues see Gut 2016; published online July 25. DOI:10.1136/gutjnl-2016-311964
85