Gluten-free diet
A gluten-free diet (GFD) is a nutritional plan that strictly excludes gluten, which is a mixture of prolamin proteins found in wheat (and all of its species and hybrids, such as spelt, kamut, and triticale), as well as barley, rye, and oats.
[10][11] In addition, a gluten-free diet may, in at least some cases, improve gastrointestinal or systemic symptoms in diseases like irritable bowel syndrome, rheumatoid arthritis, or HIV enteropathy, among others.
[18] Coeliac disease (American English: celiac) (CD) is a chronic, immune-mediated, and mainly intestinal process, that appears in genetically predisposed people of all ages.
Added difficulties for diagnosis are the fact that serological markers (anti-tissue transglutaminase [TG2]) are not always present,[25] and many people with coeliac may have minor mucosal lesions, without atrophy of the intestinal villi.
[26] Coeliac disease affects approximately 1–2% of the general population all over the world[27] and is on the increase,[28] but most cases remain unrecognized, undiagnosed and untreated, exposing patients to the risk of long-term complications.
[31] Untreated coeliac disease may cause malabsorption, reduced quality of life, iron deficiency, osteoporosis, obstetric complications (stillbirth, intrauterine growth restriction, preterm birth, low birthweight, and small for gestational age),[32] an increased risk of intestinal lymphomas and greater mortality.
[31] It is characterized by milder or even absent gastrointestinal symptoms and a wide spectrum of non-intestinal manifestations that can involve any organ of the body, and very frequently may be completely asymptomatic[29] both in children (at least in 43% of the cases[34]) and adults.
[16][35] Non-coeliac gluten sensitivity (NCGS) is described as a condition of multiple symptoms that improves when switching to a gluten-free diet, after coeliac disease and wheat allergy are excluded.
[21][40][41] Gastrointestinal symptoms may include any of the following: abdominal pain, bloating, bowel habit abnormalities (either diarrhea or constipation),[21][41] nausea, aerophagia, gastroesophageal reflux disease, and aphthous stomatitis.
[33][42] These include: headache, migraine, "brain fog", fatigue, fibromyalgia,[42][43] joint and muscle pain, leg or arm numbness, tingling of the extremities, dermatitis (eczema or skin rash), atopic disorders such as asthma, rhinitis, other allergies, depression, anxiety, iron-deficiency anemia, folate deficiency or autoimmune diseases.
[21][33][40][41][42] Above 20% of people with NCGS have IgE-mediated allergy to one or more inhalants, foods or metals, among which most common are mites, graminaceae, parietaria, cat or dog hair, shellfish and nickel.
[44] There is evidence that not only gliadin (the main cytotoxic antigen of gluten), but also other proteins named ATIs which are present in gluten-containing cereals (wheat, rye, barley, and their derivatives) may have a role in the development of symptoms.
[40][45] FODMAPs, especially fructans, are present in small amounts in gluten-containing grains and have been identified as a possible cause of some gastrointestinal symptoms in persons with NCGS.
[45][48][40] After exclusion of coeliac disease and wheat allergy,[49] the subsequent step for diagnosis and treatment of NCGS is to start a strict gluten-free diet to assess if symptoms improve or resolve completely.
[56] With gluten ataxia, damage takes place in the cerebellum, the balance center of the brain that controls coordination and complex movements like walking, speaking and swallowing, with loss of Purkinje cells.
The effectiveness of the treatment depends on the elapsed time from the onset of the ataxia until diagnosis, because the death of neurons in the cerebellum as a result of gluten exposure is irreversible.
[40] Clinicians worldwide have been challenged by an increasing number of people who do not have coeliac disease nor wheat allergy, with digestive or extra-digestive symptoms which improved removing wheat/gluten from the diet.
[60][33] Another reason that contributed to this trend was the publication of several books that demonize gluten and point to it as a cause of type 2 diabetes, weight gain and obesity, and a broad list of diseases ranging from depression and anxiety to arthritis and autism.
[40][61][68] Data from a 2015 Nielsen survey of 30,000 adults in 60 countries around the world conclude that 21% of people prefer to buy gluten-free foods, being the highest interest among the younger generations.
[67] In less developed countries, wheat can represent an important source of protein, since it is a substantial part of the diet in the form of bread, noodles, bulgur, couscous, and other products.
The potential annual financial saving to the service was estimated at £5.3 million, taking into account the reduction in cost spending and the loss of income from prescription charges.
[75] Healthcare professionals recommend against undertaking a gluten-free diet as a form of self-diagnosis,[76] because tests for coeliac disease are reliable only if the person has been consuming gluten recently.
[3] Nevertheless, the long-term effects of pure oats consumption are still unclear[79] and further studies identifying the cultivars used are needed before making final recommendations on their inclusion in the gluten-free diet.
[82] Cross-contamination occurs in these areas frequently because of a general lack of knowledge about the needed level of caution and the prevalence of gluten in restaurant kitchens.
[83] If cooks are unaware of the severity of their guest's diet restrictions or of the important practices needed to limit cross-contamination, they can unknowingly deliver contaminated food.
[86] The gluten-free diet includes naturally gluten-free food, such as meat, fish, seafood, eggs, milk and dairy products, nuts, legumes, fruit, vegetables, potatoes, pseudocereals (in particular amaranth, buckwheat, chia seed, quinoa), only certain cereal grains (corn, rice, sorghum), minor cereals (including fonio, Job's tears, millet, teff, called "minor" cereals as they are "less common and are only grown in a few small regions of the world"),[17] some other plant products (arrowroot, mesquite flour,[87] sago,[88] tapioca[88]) and products made from these gluten-free foods.
[93] It is recommended that anyone embarking on a gluten-free diet check with a registered dietitian to make sure they are getting the required amount of key nutrients like iron, calcium, fiber, thiamin, riboflavin, niacin and folate.
Several studies show an incomplete recovery of small bowel despite a strict gluten-free diet, and about 79% of such people have persistent villous atrophy.
[11][10] In addition, some people often deliberately continue eating gluten because of limited availability, inferior taste, higher price, and inadequate labelling of gluten-free products.
The European Union, World Health Organization, and Codex Alimentarius require reliable measurement of the wheat prolamins, gliadins rather than all-wheat proteins.
