Gluten is the main storage protein of wheat grains. Gluten is a complex mixture of hundreds of related but distinct proteins, mainly gliadin and glutenin. Similar storage proteins exist as secalin in rye, hordein in barley, and avenins in oats and are collectively referred to as “gluten.
” The objective was to discuss the biochemical and functional properties of the gluten proteins, including structure, sources, and dietary intakes. Literature was reviewed from food science and nutrition journals. The gluten protein networks vary because of different components and sizes, and variability caused by genotype, growing conditions, and technological processes.
The structures and interactions of this matrix contribute to the unique properties of gluten. The resulting functions are essential to determining the dough quality of bread and other baked products.
Gluten is heat stable and has the capacity to act as a binding and extending agent and is commonly used as an additive in processed foods for improved texture, moisture retention, and flavor. Gliadin contains peptide sequences that are highly resistant to gastric, pancreatic, and intestinal proteolytic digestion in the gastrointestinal tract.
The average daily gluten intake in a Western diet is thought to be 5–20 g/day and has been implicated in several disorders. Gluten containing grains (wheat, rye, barley, and oats) are important staple foods. Gluten is among the most complex protein networks and plays a key role in determining the rheological dough properties.
Wheat is one of world's major food crops, cultivated, consumed, and traded worldwide. The common wheat species (Triticum aestivum L.) is often used to describe many other cultivated wheat species and genotypes.
The wheat kernel contains 8%–15% of protein, from which 10%–15% is albumin/globulin and 85%–90% is gluten (Fig. 1).1 Gluten is a complex mixture of hundreds of related but distinct proteins, mainly gliadin and glutenin.
Different wheat varieties vary in protein content and in the composition and distribution of gluten proteins.
1 Collectively, the gliadin and glutenin proteins are referred to as prolamins, which represent seed proteins insoluble in water, but extractable in aqueous ethanol and are characterized by high levels of glutamine (38%) and proline residues (20%).1
Approximate breakdown of wheat components.
The gluten proteins can be classified into subgroups dependent on key differences including sulfur content and molecular weight and then further classified according to their different primary structures into alpha, beta, gamma, and omega (α, β, γ, and ω) gliadins.2 Individual gluten proteins are bound by strong covalent and non‐covalent forces, which, together with the structure and interaction of these proteins, contribute to the unique properties of gluten.2
The gluten matrix and its resulting functions are essential to determining the dough quality of bread and other baked products such as pasta, cakes, pastries, and biscuits.
Gluten is heat stable and has the capacity to act as a binding and extending agent and is commonly used as an additive in processed foods for improved texture, flavor, and moisture retention.
Therefore, less obvious sources of gluten include processed meat, reconstituted seafood, and vegetarian meat substitutes; and as thickeners, emulsifiers, or gelling agents in candies, ice cream, butter, seasonings, stuffings, marinades and dressings; and as fillers and coatings used in medications or confectionary. In addition, gluten is increasingly separated from wheat (known as “vital wheat gluten”) or modified for specific uses (known as “isolated wheat proteins”) to improve the structural integrity of industrial bakery products and to fortify low‐protein flours.3
The unusual rheological and functional properties of gluten are dependent upon the ratio of glutenins to gliadins, and the interactions of these structures. Each component has slightly different functions crucial in determining the viscoelastic properties (entrapment of carbon dioxide released during bread leavening) and quality of the end product.
For example, purified hydrated gliadins contribute more to the viscosity and extensibility of the dough, whereas hydrated glutenins are cohesive and contribute to dough strength and elasticity.1 Much work has focused on improving dough strength, for example, increasing the high molecular weight subunit gene copy number to improve glutenin elasticity.
Similar proteins to the gliadin found in wheat exist as secalin in rye, hordein in barley, and avenins in oats and are collectively referred to as “gluten.
” Derivatives of these grains such as triticale and malt and other ancient wheat varieties such as spelt and kamut also contain gluten.
The gluten found in all of these grains has been identified as the component capable of triggering the immune‐mediated disorder, coeliac disease.
Gluten is a very complex compound, characterized by high allelic polymorphism encoding its specific proteins, glutenin, and gliadin. Furthermore, each wheat genotype produces unique types and quantities of these compounds, which can also differ by varied growing conditions and technological processes.
The protein (and also carbohydrate) expression of one genotype can change depending on the environment where it was grown, for example, the ω‐5 gliadin content increases with fertilization and temperature during maturity.
3 Some of the α gliadins located in the subaleurone of the wheat kernel can be partially removed by roller milling.
Gliadin contains peptide sequences (known as epitopes) that are highly resistant to gastric, pancreatic, and intestinal proteolytic digestion in the gastrointestinal tract, escaping degradation in the human gut.
This difficult digestion is due to gliadin's high content of the amino acids, proline, and glutamine, which many proteases are unable to cleave.
5 These proline‐rich residues create tight and compact structures that can mediate the adverse immune reactions in coeliac disease.
A variety of sequences from α, γ, and ω gliadins, as well as from the glutenins, have been identified to activate coeliac disease. However, several hundred gluten peptides are predicted to be immunogenic and trigger the T‐cell mediated response.
6 The most immunodominant T‐cell epitope is from α gliadin, although T‐cell cross‐reactivity against gluten‐derived, secalin‐derived, and hordein‐derived peptides have been confirmed. Additionally, within each grain, there exists a distinct hierarchy of immunostimulatory gluten peptides.
6 Of all the peptides known to stimulate the T‐cell response in coeliac disease, a given patient may react to only a few.
What Is Gluten? Definition, Foods, and Side Effects
Written by Ansley Hill, RD, LD on December 13, 2019 — Medically reviewed by Kathy W. Warwick, R.D., CDE
- What it is
- Food sources
- Medical conditions
- Bottom line
Gluten-free diets are becoming increasingly popular, especially due to the growing awareness surrounding gluten intolerance.
In turn, this has fueled a rapid rise in the mainstream availability of gluten-free food options. In fact, the gluten-free food industry grossed over $15 billion in sales in 2016 (1).
The introduction of these products took what was once an extraordinarily difficult diet to follow and made it much simpler and considerably more accessible for the many people who need it.
This article reviews everything you need to know about gluten, including what it is, which foods contain it, and how it may affect those with gluten intolerance.
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- Gluten is a family of storage proteins — formally known as prolamins — that are naturally found in certain cereal grains, such as wheat, barley, and rye (2).
What Is Gluten?
Gluten refers to the proteins in cereal grains, such as wheat, barley and rye. Gluten is found in the endosperm (a type of tissue produced in seeds that are ground to make flour) and nourishes plant embryos during germination. Later on, gluten affects the elasticity of dough, acting as a glue to hold the food together, which in turn affects the chewiness of baked products.
Gluten is a mixture of hundreds of distinct proteins within the same family, although it is primarily made up of two different classes of proteins: gliadin, which gives bread the ability to rise during baking, and glutenin, which is responsible for dough's elasticity.
Not all grains contain gluten. Some examples of gluten-free grains are sorghum, millet, brown rice, buckwheat, wild rice, amaranth, quinoa, corn (polenta) and teff. Oats are also gluten-free, but can be contaminated during processing, said Lori Chong, a registered dietitian.
Is gluten bad?
Gluten is only bad for certain people. These people are gluten-sensitive or gluten-intolerant, which means their bodies produce an abnormal immune response when breaking down gluten during digestion. About 18 million Americans have gluten sensitivity, according to the National Foundation for Celiac Awareness.
The most well-known form of gluten intolerance is celiac disease, which affects one in every 141 people in the United States, according to the U.S. Department of Health and Human Services. When someone with celiac disease consumes gluten, it triggers an immune response that damages their intestines, preventing them from absorbing vital nutrients.
The chronic gastrointestinal disorder called irritable bowel syndrome (IBS) is another condition that is affected by gluten.
IBS affects 7 to 20 percent of adults in the United States, according to a paper published in the journal Gastroenterology & Hepatology.
Chong explained that gluten grains are high in starches and sugars that can be easily fermented by intestinal bacteria. This can cause bloating, cramping and/or diarrhea.
Wheat allergy is a rare type of allergy that is marked by skin, respiratory or gastrointestinal reactions to wheat allergens, but is not necessarily caused by gluten. According to the American College of Allergy, Asthma and Immunology, 65 percent of children with a wheat allergy outgrow it by age 12.
Recently, scientists have become aware of another potential form of intolerance called non-celiac gluten sensitivity (NCGS). After consuming gluten, patients with gluten sensitivity may experience many celiac disease symptoms, such as diarrhea, fatigue and joint pain, but don't appear to have damaged intestines.
These symptoms can be due to poor digestion or a placebo effect. According to a 2015 study, NCGS appears to be more common in females and young to middle-age adults.
The study also questions what percentage of the population actually has NCGS, as many patients appear to diagnose and treat themselves with a gluten-free diet without consulting their doctor.
The effects of going gluten-free
In cases of gluten intolerance, doctors typically recommend a gluten-free diet.
Patients must avoid eating any foods and ingredients that contains gluten, including bread, beer, French fries, pasta, salad dressing, soy sauce and even some soups (unless otherwise marked as “gluten-free”).
According to the U.S. Food and Drug Administration, food products must contain less than 20 ppm of gluten in order to be labeled gluten-free.
In recent years, many people without gluten intolerance have taken up gluten-free diets. In fact, according to the Mayo Clinic, 80 percent of people on gluten-free diets do not have a celiac disease diagnosis.
Experts worry, however, that going on these diets without explicitly needing to could be detrimental to a person's health, as gluten-free foods are often nutrient-deficient. Dr.
Refaat Hegazi, medical director for Abbott's Adult Nutrition, says that going gluten-free can affect the body in many ways.
Gluten: What is it and why is it bad for some people?
Medically reviewed by Adrienne Seitz, MS, RD, LDN — Written by Adda Bjarnadottir, MS, RDN (Ice) — Updated on May 14, 2020
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Gluten is controversial these days. Most sources claim that it is safe for everyone except those who have celiac disease. On the other hand, some health experts believe that gluten is harmful to most people.
According to a 2013 survey, more than 30% of Americans actively try to avoid eating gluten (1).
This article explains what gluten is and how it can affect people’s health.
Share on PinterestCertain grains, such as wheat and rye, contain gluten.
Gluten is a family of proteins found in grains, including wheat, rye, spelt, and barley.
Of the gluten-containing grains, wheat is by far the most common.
The two main proteins in gluten are glutenin and gliadin. Gliadin is responsible for most of the adverse health effects of gluten (2, 3).
What is Gluten? | Celiac Disease Foundation
Gluten is a general name for the proteins found in wheat (wheatberries, durum, emmer, semolina, spelt, farina, farro, graham, KAMUT® khorasan wheat and einkorn), rye, barley and triticale – a cross between wheat and rye. Gluten helps foods maintain their shape, acting as a glue that holds food together. Gluten can be found in many types of foods, even ones that would not be expected.
Wheat is commonly found in:
- baked goods
- salad dressings
Barley is commonly found in:
- malt (malted barley flour, malted milk and milkshakes, malt extract, malt syrup, malt flavoring, malt vinegar)
- food coloring
- Brewer’s Yeast
Rye is commonly found in:
- rye bread, such as pumpernickel
- rye beer
Definition of gluten
/ ˈglut n /SEE SYNONYMS FOR gluten ON THESAURUS.COMthe tough, viscid, nitrogenous substance remaining when the flour of wheat or other grain is washed to remove the starch. Archaic. glue or a gluey substance.
First recorded in 1590–1600, gluten is from the Latin word glūten gluegluteal, gluteal artery, gluteal fold, gluteal furrow, glutelin, gluten, gluten bread, gluten enteropathy, glutenin, glutenous, gluteofemoralDictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc.
2020grass, cereal, durum, spelt, semolina
- She's happy to accommodate vegetarians, vegans, and those intolerant of gluten.
- “It is important to know that gluten is not absorbed through the skin,” she wrote in response to my questions.
- That do not meet the dietary needs of those who are gluten intolerant.
- Anyone who suffers from gluten sensitivity, intolerance, or celiac disease knows how troublesome the problem is.
- Gluten is a protein primarily found in wheat, barley, and rye.
- The first or outer one contains the bran; second, the gluten, fats and salts; third, the starch.Public School Domestic Science|Mrs. J. Hoodless
- Change in the solubility of the gluten proteins, due to the action of the organic acids and fermentation.Human Foods and Their Nutritive Value|Harry Snyder
- The most nutritious grasses are those which abound in sugar, starch, and gluten.The American Reformed Cattle Doctor|George Dadd
- It contains no azote, for it affords no ammonia by distillation, and is therefore very dissimilar to gluten.A Dictionary of Arts, Manufactures and Mines|Andrew Ure
- After 30 minutes obtain the gluten by washing, being careful to remove all the starch and prevent any losses.Human Foods and Their Nutritive Value|Harry Snyder
a protein consisting of a mixture of glutelin and gliadin, present in cereal grains, esp wheat. A gluten-free diet is necessary in cases of coeliac diseaseCollins English Dictionary – Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012A mixture of insoluble plant proteins occurring in cereal grains, chiefly corn and wheat, used as an adhesive and as a flour substitute.The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.The mixture of proteins, including gliadins and glutelins, found in wheat grains, which are not soluble in water and which give wheat dough its elastic texture.Any of the prolamins found in cereal grains, especially the prolamins in wheat, rye, barley, and possibly oats, that cause digestive disorders such as celiac disease.The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
WORD OF THE DAY
osmaticadjective | [oz-mat-ik]SEE DEFINITION
Ditch the Gluten, Improve Your Health?
By: Robert Shmerling, M.D.
This just in: A new health myth has been taking the country by storm.
Perhaps I'm exaggerating a bit. After all, health fads— especially diet fads— have come and gone for decades. Some are more worthy than others. For example, I am impressed by the evidence supporting the Mediterranean diet as a healthy option.
As each one of us is different, the “ideal diet” may not be the same for each person. But the interest and enthusiasm surrounding the gluten-free food movement in recent years has been remarkable. Not so long ago, relatively few people had ever heard of gluten.
And it certainly wasn't the “food movement” it has recently become.
If you're considering limiting your consumption of gluten, you're certainly not alone. But the question is: Will restricting the gluten you eat improve your health? And will it make you feel better? It's appealing to think so.
What Is Gluten?
Gluten is a protein found in many grains, including wheat, barley and rye. It's common in foods such as bread, pasta, pizza and cereal. Gluten provides no essential nutrients. People with celiac disease have an immune reaction that is triggered by eating gluten.
They develop inflammation and damage in their intestinal tracts and other parts of the body when they eat foods containing gluten. Current estimates suggest that up to 1% of the population has this condition. A gluten-free diet is necessary to eliminate the inflammation, as well as the symptoms.
Grocery stores and restaurants now offer gluten-free options that rival conventional foods in taste and quality; in years past, it was much harder to maintain a gluten-free diet.
So, maybe it should come as no surprise that people would embrace the gluten-free mantra. And embrace it they have.
According to a survey by the Consumer Reports National Research Center published in 2014 a full 63% of Americans believe that a gluten-free diet could improve their mental or physical health.
And up to a third of Americans are cutting back on it in the hope that it will improve their health or prevent disease.
Is This Really a Myth?
To call something a myth, it's important to define the term. My non-scientific definition of a health myth requires most of the following:
- Many people believe it.
- There is no compelling scientific evidence to support it.
- There is at least some scientific evidence against it.
- There is a pseudo-scientific explanation that may have intuitive appeal (for example, enemas to “detoxify” the colon).
- The idea defies standard understanding of biology or has no reasonable biologic explanation. An example is a diet that is said to help you lose weight despite increasing your caloric intake and reducing exercise.
Three other features of many popular health myths include:
- The possibility that it can actually harm you
- A profit motive (by those promoting the myth)
- Celebrity endorsement
From this definition, the notion that a gluten-free diet will improve health is a certifiable health myth for most people.
Who Should Avoid Gluten?
There is at least some truth to the idea that gluten can be harmful. As mentioned, people with celiac disease avoid sickness and maintain much better health if they follow a gluten-free diet. For them, a gluten-free diet is nothing short of essential.
And then there are people described as “gluten-sensitive.” Their tests for celiac disease are negative (normal) and yet they get symptoms (including bloating, diarrhea or crampy abdominal pain) whenever they eat foods that contain gluten.
One cause is wheat allergy, a disorder that can be diagnosed by skin testing. But for many, the diagnosis remains uncertain.
Some have begun calling this “non-celiac gluten hypersensitivity,” a poorly defined condition about which we have much to learn.
Avoiding gluten makes sense for people with celiac disease, wheat allergy or those who feel unwell when they consume gluten.
What About Everyone Else?
There is no compelling evidence that a gluten-free diet will improve health or prevent disease if you don't have celiac disease and can eat gluten without trouble. Of course, future research could change this. We may someday learn that at least some people without celiac disease or symptoms of intestinal disease are better off avoiding gluten.
So Why Are Gluten-Free Diets So Popular?
I suspect the popularity relates to a combination of factors, including: