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Gluten intolerance, hazards and risks

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Context - Gluten is a protein found in wheat and some other cereals that are widely used in western diets. How widespread are the digestive problems that are associated with gluten?

What is intolerance to gluten?

This is a faithful summary of the leading report produced in 2011 by the US Food and Drug Administration (US-FDA): " Health Hazard Assessment for Gluten Exposure in Individuals with Celiac Disease: Determination of Tolerable Daily Intake Levels and Levels of Concern for Gluten" 

  • Source document:US-FDA (2011)
  • Summary & Details: GreenFacts
Latest update: 11 March 2016


Gluten is a mixture of proteins that are found in wheat, but also barley, rye and other cereals. For some people, who have a genetic predisposition (about 1% of the population in the US) , exposure to gluten leads to the development of celiac disease (CD). CD is a permanent hypersensitivity reaction that affects the small intestine and can also induce a type of autoimune dermatitis.

What is gluten?

Gluten is a component of wheat that consists of complex mixture of storage proteins. Similar proteins are found in rye and barley. Technically, only the proteins in wheat are called gluten, but those in rye and barley also trigger the hypersensitivity reactions, and so are considered as ‘gluten’ when it comes to celiac disease. In food made from wheat, rye, barley, triticale, and oats, the simple presence of "proteins" in that food usually means that gluten may be present.

Oats are usually tolerated in moderate amounts (e.g., 50-70 grams daily) by sensitive individuals with CD, but many oat products also contain traces of wheat, rye, or barley due to cross-contact with these grains during growth, harvest, transport, storage, or processing.

What is the Celiac Disease(CD)?

Celiac disease is a permanent hypersensitivity reaction triggered in genetically predisposed individuals (estimated at 1% in the U.S.) by ingestion of gluten present in wheat, barley, and rye. It is a serious illness that also has a connection with a number of other disorders and diseases.

A significant part of the genetic predisposition to CD is associated with specific genes but other factors may also have a determining influence on disease susceptibility which include environmental factors (e.g., breast-feeding can lower the risk, infections can increase it), abnormalities in the immune system and certain genetic based syndromes.

A large number of individuals are believed to have "silent" celiac disease, which means that they do not suffer from direct digestive symptoms such as diarrhea, but still have problems with their intestines. For those people, a correct diagnosis for their illness can take years.

It is important to underline that for people who do not have the genetic predisposition for developing CD (99% in the US), exposure to gluten causes no detrimental health problems.

What are the main symptoms of Celiac Disease?

Celiac disease is a progressive series of changes in the small intestine mucosa that result in a number of digestive symptoms.

The usual symptoms of CD include chronic diarrhea or constipation, steatorrhea (abnormal amounts of fat in the feces), recurrent abdominal distension or abdominal pain, nausea and/or vomiting. Associated with this disfunction of the intestines are symptoms such as anemia, nutritional deficiencies, growth disturbances, weight loss and bone density problems (osteoporosis). Other signs include fatigue, irritability, malaise, anorexia, mouth ulcers, headaches, mood changes, depression, and pain. CD is also associated with an increased risk of developing other diseases such as autoimmune conditions, bone diseases and cancers.

This disease is often misdiagnosed given that other disorders such as irritable bowel syndrome, present similar clinical symptoms.

What are the criteria used to identify a Celiac Disease (CD)?

  • The performance of a small intestinal biopsy while individuals are consuming a gluten-containing diet, and the observation of abnormal mucosal morphology.
  • The resolution of clinical symptoms in patients within weeks or months of a gluten free diet supports the diagnosis of CD.
  • A formal « gluten challenge » and some additional measures and tests such as the use of antibody tests have been suggested as adjunct measures to support a CD diagnosis.

The responses of subjects to challenge tests vary widely between subjects and may differ between children and adults.

What are the Tolerable Daily Intake doses for Gluten in sensitive subjects?

Globally, a level of less than 1 mg of gluten per kg food (or ppm) is the level of exposure that protects the most sensitive individuals with Celiac disease. It thus protects the largest number of individuals with CD from experiencing any detrimental health effects.

In this risk assessment, the Level of Concern values for exposure to rye and barley are taken as being equivalent to those for the consumption of wheat.

Because of the significant degree of individual variability in the sensitivity and responsiveness to gluten, other uncertainty factors than those used for this estimation may be warranted to provide a sufficient level of protection for the most gluten-sensitive individuals.

Are there other health effects induced by gluten intolerance?

Another chronic condition associated with exposure to gluten is Dermatitis Herpetiformis (DH). It is an autoimmune skin disease that results in itchy blisters that are intensely located in a symmetrical fashion on the extensor surface of the elbows and knees in addition to the lower back or buttocks, scalp of the back of the head and posterior neck.

Other medical conditions are also associated with celiac disease :

  • Autoimmune Diseases: a number of autoimmune diseases are more likely to occur in patients with CD than in the general population;
  • Bone Diseases: CD is often accompanied by secondary diseases that reflect the existence of abnormalities in bone metabolism;
  • Cancers: some cancers of the digestive system occur more often in people with CD;

People with celiac disease have a mortality rate that is higher than the general population, which has been attributed to the associations of celiac disease with the development of autoimmune diseases and/or cancer.

What is the effective treatment for Celiac Disease (CD)?

The only effective treatment currently available is a gluten-free diet that permanently eliminates wheat, rye and barley. However, it has been recognized that it is difficult, if not impossible, to maintain a diet that is completely devoid of gluten. Globally, a less than 1 mg gluten/kg food (or ppm) level of gluten in foods is the level at which the most sensitive people will not experience symptoms.

Cereal grains assumed to be safe for people with celiac disease include amaranth, buckwheat, corn, Indian ricegrass, Job's tears, millet, quinoa, ragi, rice, sorghum, teff (or tef), and wild rice.

Although the rate of recovery varies between individuals, this treatment is associated with decreases in symptoms and reports of improved quality of life. If a person with CD on a gluten-free diet starts to eat gluten again, then the symptoms come back.

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