Gluten-free diet

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Wheat

A gluten-free diet (GFD) is a diet that excludes gluten, a protein composite found in wheat, barley, rye,[1][2] and all their species and hybrids (such as spelt,[1] kamut, and triticale[1][2]). The inclusion of oats in gluten-free diet remains controversial. Avenin present in oats may be also toxic for coeliac people.[2] Its toxicity depends on the cultivar consumed.[3] Furthermore, oats is frequently cross contaminated with gluten-containing cereals.[2]

Gluten causes health problems in sufferers of gluten-related disorders, which include coeliac disease (CD), non-celiac gluten sensitivity (NCGS), gluten ataxia, dermatitis herpetiformis (DH) and wheat allergy.[4] In these patients, the gluten-free diet is a demonstrated effective treatment.[5][6][7] In addition, at least in some cases, the gluten-free diet may improve gastrointestinal and/or systemic symptoms in other diseases, such as irritable bowel syndrome, rheumatoid arthritis, multiple sclerosis or HIV enteropathy, among others.[8]

Gluten proteins have low nutritional and biological value, and are not essential in the diet.[9] However, an unbalanced selection of food and an incorrect choice of commercially prepared gluten-free replacement products, which are poorer nutritional quality and have greater lipid / carbohydrate content compared to the gluten-containing counterparts, may lead to nutritional deficiencies. These nutritional complications can be prevented by a correct dietary education. Gluten free-diet must be mainly based on naturally gluten-free foods, which are more equilibrate in micro and macro nutrients, such as meat, fish, eggs, legumes, nuts, fruits, vegetables, potatoes, rice, maize. It is advisable to choose commercially prepared gluten-free replacement products that are enriched or fortified with vitamins and minerals.[2] Furthermore, a healthy alternative to these products are pseudocereals (such as quinoa, amaranth and buckwheat) and other minor cereals, which have high biological and nutritional value.[2][9]

Rationale behind adoption of the diet

One breadcrumb of this size contains enough gluten to cause significant digestive discomfort in people with gluten-related disorders when they are following a gluten-free diet. Consuming gluten even in small quantities, which may be the result of inadvertent cross-contamination, causes active immune response and carries the risk of triggering associated diseases.[10][11][12][13][14]

Coeliac disease

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Coeliac disease (American English: celiac) (CD) is a chronic, immune-mediated mainly intestinal process, caused by the ingestion of wheat, barley, rye and derivatives, that appears in genetically predisposed people of all ages. CD is not only a gastrointestinal disease, because it may involve to several organs and cause an extensive variety of non-gastrointestinal symptoms, and most importantly, it may often be completely asymptomatic.[15] Added difficulties for diagnosis are the fact that serological markers (anti-tissue transglutaminase [TG2]) are not always present[16] and many patients may have minor mucosal lesions, without atrophy of the intestinal villi.[17]

CD affects approximately 1-2% of general population all over the world[18] and appears to be on the increase,[19] but most cases remain unrecognized, undiagnosed and untreated, and exposed to the risk of long-term complications.[20][21] Patients may suffer severe disease symptoms and be subjected to extensive investigations for many years, before a proper diagnosis is achieved.[22] Untreated CD may cause malabsorption, reduced quality of life, iron deficiency, osteoporosis,[15] obstetric complications (stillbirth, intrauterine growth restriction, preterm birth, low birthweight, and small for gestational age),[23] an increased risk of intestinal lymphomas[15] and greater mortality.[24] CD is associated with some autoimmune diseases, such as diabetes mellitus type 1, thyroiditis,[15][25] gluten ataxia, psoriasis, vitiligo, autoimmune hepatitis, dermatitis herpetiformis, primary sclerosing cholangitis, and more.[25]

CD with “classic symptoms”, which include gastrointestinal manifestations such as chronic diarrhea and abdominal distention, malabsorption, loss of appetite, and impaired growth, is currently the least common presentation form of the disease and affects predominantly to small children generally younger than two years of age.[20][22]

CD with “non-classic symptoms” is the most common clinical found type[22] and occurs in older children (over 2 years old),[22] adolescents and adults.[22] 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[20] both in children (at least in 43% of the cases[26]) and adults.[20]

Following a lifelong gluten-free diet is the only medically-accepted treatment for people with coeliac disease.[9][27]

Non-celiac gluten sensitivity

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Non-celiac gluten sensitivity (NCGS) is described as a condition of multiple symptoms that improves when switching to a gluten-free diet, after celiac disease and wheat allergy are excluded.[28][29] Patients may develop gastrointestinal symptoms, which resemble those of irritable bowel syndrome (IBS)[30][31] and/or a variety of nongastrointestinal symptoms.[12][32][33]

Gastrointestinal symptoms may include any of the following: abdominal pain, bloating, bowel habit abnormalities (either diarrhea or constipation),[12][33] nausea, aerophagia, gastroesophageal reflux disease, and aphthous stomatitis.[32][33] Extra-intestinal symptoms, which can be the only manifestation of NCGS even in absence of gastrointestinal sympotms, may be any of the following: headache or migraine, “foggy mind”, fatigue,[12][32][33] fibromyalgia,[12][34][35] joint and muscle pain,[12][32][33] leg or arm numbness,[12][32][33] tingling of the extremities,[32][33] dermatitis (eczema or skin rash),[32][33] atopic disorders,[32] allergy to one or more inhalants, foods or metals[12][32] (such as mites mites, graminaceae, parietaria, cat or dog hair, shellfish, or nickel),[12] depression,[12][32][33] anxiety,[12] anemia,[32][33] iron-deficiency anemia, folate deficiency, asthma, rhinitis, eating disorders,[12] or autoimmune diseases.[32]

NCGS seems to be involved in some neuropsychiatric disorders, principally schizophrenia,[24][33] autism[12][24][33] and peripheral neuropathy,[24][33] and also ataxia[24] and attention deficit hyperactivity disorder (ADHD).[32]

The pathogenesis of NCGS is not yet well understood. It was hypothesized that gluten, like occurs in coeliac disease, is the cause of NCGS.[32] Much recent research on NCGS has aimed at determining which agents trigger a response in NCGS patients: to which extent gluten, FODMAPs, or ATIs (plant-derived proteins present in glutencontaining cereals and gluten) or other substances are involved.[33] In a 2013 double-blind placebo-controlled trial (DBPC) by Biesiekierski et al. in a few patients with irritable bowel syndrome (IBS), the authors found no difference between gluten or placebo groups and the concept of NCGS as a syndrome was questioned. Nevertheless, this study had design errors and an incorrect selection of participants, which could have masked the true effect of gluten reintroduction.[21][36] In a review of May 2015 published in Gastroenterology, Fasano et al. conclude that besides gluten, ATIs and FODMAPs present in gluten, wheat, barley, rye, and their derivatives play a role in the deveolpment of NCGS symptoms. ATIs, which resist proteolytic digestion, may be the inducers of innate immunity in people with coeliac disease or NCGS. FODMAPs cause mild wheat intolerance at most, which is mainly limited to gastrointestinal symptoms.[32]

There is a mistaken idea that NCGS patients don’t need strictly following gluten-free diet. Nevertheless, as occurs in people with coeliac disease, the diet must be strict and maintained, without making any dietary transgression. The ingestion of even small amounts of gluten can cause more immediate and obvious symptoms in people with NCGS than those with coeliac disease.[12] It is not yet known whether NCGS is a permanent, or a transient condition.[12][26]

Also, a subgroup of NCGS patients may not improve by eating commercially available gluten-free products, which are usually rich of preservatives and additives, because chemical additives (such as sulphites, glutamates, nitrates and benzoates) might have a role in evoking functional gastrointestinal symptoms of NCGS. These patients may benefit from a diet with a low content of preservatives and additives.[37]

NCGS, which is possibly immune-mediated, now appears to be more common than coeliac disease,[38] with a prevalence estimated to be 6-10 times higher.[39]

Wheat allergy

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People can also experience adverse effects of wheat as result of a wheat allergy.[21] Gastrointestinal symptoms of wheat allergy are similar to those of coeliac disease and non-celiac gluten sensitivity, but there is a different interval between exposure to wheat and onset of symptoms. Wheat allergy has a fast onset (from minutes to hours) after the consumption of food containing wheat and could be anaphylaxis.[16][40]

The treatment of wheat allergy consists of complete withdrawal of any food containing wheat and other gluten-containing cereals.[6][40] Nevertheless, some patients can tolerate barley, rye or oats.[41]

As a fad diet

Gluten-free fad diets are endorsed by celebrities such as Miley Cyrus,[42] and are used by some world class athletes who believe the diet can improve energy and health.[43] The book Wheat Belly which refers to wheat as a "chronic poison" became a New York Times bestseller within a month of publication in 2011.[44] People buy gluten-free food "because they think it will help them lose weight, because they seem to feel better or because they mistakenly believe they are sensitive to gluten."[45] It should not be undertaken to diagnose one's own symptoms,[46] because tests for celiac disease are reliable only if the patient has been consuming gluten.

Although popularly used as an alternative treatment for people with autism, there is no good evidence that a gluten-free diet is of benefit in treating the symptoms of autism.[47][48][49] However, in a subset of autistic patients who have a genuine gluten sensitivity there is limited evidence that suggests that a gluten free diet may improve some autistic behaviours.[12][31][35][49]

This diet adds a financial burden to those who think they can only solve their health issues by cutting gluten out of their diet. There is a consensus in the medical community that people should consult a physician before going on a gluten-free diet, so that a medical professional can accurately test for Coeliac disease or any other gluten-induced health issues.[50]

In a review of May 2015 published in Gastroenterology, Fasano et al. conclude that although there is an evident "fad component" to the recent rise popularity of the gluten-free diet, there are also growing and unquestionable evidences about the existence of non-celiac gluten sensitivity.[51]

Eating gluten-free

Quinoa is a pseudocereal that is gluten-free.

The gluten-free diet includes naturally gluten-free food, such as meat, fish, 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"),[52] some other plant products (arrowroot, mesquite flour[53]) and products made from these gluten-free foods, such as breads and gluten-free beer. Gluten-free bread may be less fluffy, so additives are used to compensate, such as corn starch, eggs, xanthum gum, guar gum, and hydroxypropyl methylcellulose.

Processing of some glutenous ingredients removes the gluten, such as maltodextrin, and some distilled beverages.[54]

Some vineyards use flour paste to caulk the oak barrels, but tests have not detected the presence of gluten in the wine.[55] Gluten may be used as a clarifying agent in wine, some of which might remain in the product.[56]

The diet excludes foods containing gluten, such as wheat, rye, barley, triticale, kamut, malt,[52] and foods that may include them, or shared transportation or processing facilities with them.[57]

Some cereal grains, although gluten-free in themselves, may contain gluten by cross-contamination during processing steps or transport; this includes oats.[58] Some processed foods may contain gluten, so they would need specific labeling, such as gluten-free ice-cream, ketchup, chicken bouillon, corn cereal, ice cream toppings, malt flavoring, and chocolate. And some non-foodstuffs may contain gluten as an excipient or binding agent, such as medications and vitamin supplements, especially those in tablet form.[59][60] People with gluten intolerance may require special compounding of their medication.[57]

Risks

Unless great care is taken, a gluten-free diet can lack the vitamins, minerals, and fiber which are found in wheat, barley, rye, kamut, and other gluten-containing whole grains[61] and may be too high in fat and calories.[53][62] Processed gluten-free foods are often higher in salt, sugar, glycemic index, transfats and other processed fats.[53] Although the lack of vitamins, minerals and fiber can be mitigated through the consumption of brown rice and quinoa,[63] many practitioners of the diet do not consume the recommended number of grain servings per day.[64][65] Many gluten-free products are not fortified or enriched by such nutrients as folate, iron, and fiber as traditional breads and cereals have been during the last century.[66]

Advances towards higher nutrition-content gluten-free bakery products, improved for example in terms of fiber content and glycemic index, have been made by using not exclusively corn starch or other starches to substitute for flour. In this aim, for example the dietary fiber inulin (which acts as a prebiotic[67]) or quinoa or amaranth wholemeal have been as substitute for part of the flour. Such substitution has been found to also yield improved crust and texture of bread.[68]

Regulation and labels

The term gluten-free is generally used to indicate a supposed harmless level of gluten rather than a complete absence.[11] The exact level at which gluten is harmless is uncertain and controversial. A 2008 systematic review tentatively concluded that consumption of less than 10 mg (10 ppm) of gluten per day is unlikely to cause histological abnormalities, although it noted that few reliable studies had been done.[11]

Regulation of the label gluten-free varies by country. Most countries derive key provisions of their gluten-free labeling regulations from the Codex Alimentarius international standards for food labeling has a standard relating to the labeling of products as gluten-free. It only applies to foods that would normally contain gluten.[69] Gluten-free is defined as 20 ppm (= 20 mg/kg) or less. It categorizes gluten-free food as:

  • Food that is gluten-free by composition
  • Food that has become gluten-free through special processing.
  • Reduced gluten content, food which includes food products with between 20 and 100 ppm of gluten. Reduced gluten content is left up to individual nations to more specifically define.

The Codex Standard suggests the enzyme-linked Immunoassay (ELISA) R5 Mendez method for indicating the presence of gluten, but allows for other relevant methods, such as DNA. The Codex Standard specifies that the gluten-free claim must appear in the immediate proximity of the name of the product, to ensure visibility.

There is no general agreement on the analytical method used to measure gluten in ingredients and food products.[70] The ELISA method was designed to detect w-gliadins, but it suffered from the setback that it lacked sensitivity for barley prolamins.[71] The use of highly sensitive assays is mandatory to certify gluten-free food products. The European Union, World Health Organization, and Codex Alimentarius require reliable measurement of the wheat prolamins, gliadins rather than all-wheat proteins.[72]

Australia

The Australian government recommends[73] that:

  • food labeled gluten-free include no detectable gluten (<5ppm [citation needed]), oats or their products, cereals containing gluten that have been malted or their products
  • food labeled low gluten claims such that the level of 20 mg gluten per 100 g of the food

Brazil

All food products must be clearly labelled whether they contain gluten or they are gluten-free.[74]

Canada

Health Canada considers that foods containing levels of gluten not exceeding 20 ppm as a result of contamination, meet the health and safety intent of section B.24.018 of the Food and Drug Regulations when a gluten-free claim is made.[75] Any intentionally added gluten, even at low levels must be declared on the packaging and a gluten-free claim would be considered false and misleading. Labels for all food products sold in Canada must clearly identify the presence of gluten if it is present at a level greater than 10 ppm.[76]

European Union

The EU European Commission delineates[77] the categories as:

  • gluten-free: 20 ppm or less of gluten
  • very low gluten foodstuffs: 20-100ppm gluten.

In the United Kingdom, only cereals must be labelled; labelling of other products is voluntary.[78]

United States

Until 2013 anyone could use the gluten-free claim with no repercussion. In 2008, Wellshire Farms chicken nuggets labeled gluten-free were purchased and samples were sent to a food allergy laboratory[79] where they were found to contain gluten. After this was reported in the Chicago Tribune, the products continued to be sold. The manufacturer has since replaced the batter used in its chicken nuggets.[80] The U.S. first addressed gluten-free labeling in the 2004 Food Allergen Labeling and Consumer Protection Act (FALCPA). The Alcohol and Tobacco Tax and Trade Bureau published interim rules and proposed mandatory labeling for alcoholic products in 2006.[81] The FDA issued their Final Rule on August 5, 2013.[82] When a food producer voluntarily chooses to use a gluten-free claim for a product, the food bearing the claim in its labeling may not contain:

  • an ingredient that is a gluten-containing grain
  • an ingredient that is derived from a gluten-containing grain that has not been processed to remove gluten
  • an ingredient that is derived from a gluten-containing grain, that has been processed to remove gluten but results in the presence of 20 ppm or more gluten in the food. Any food product claiming to be gluten-free and also bearing the term "wheat" in its ingredient list or in a separate "Contains wheat" statement, must also include the language "*the wheat has been processed to allow this food to meet the FDA requirements for gluten-free foods," in close proximity to the ingredient statement.
  • Any food product that inherently does not contain gluten may use a gluten-free label where any unavoidable presence of gluten in the food bearing the claim in its labeling is below 20 ppm gluten.

See also

External links

References

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