Wheat, Gluten, & Health

The number of people in the United States diagnosed with celiac disease—an autoimmune condition triggered by gluten, a group of proteins in wheat and related cereal grains—has increased significantly in recent decades, due to a combination of increased awareness of the disease and a rise in celiac prevalence for unknown reasons. At the same time, amidst increasing popularity of gluten-free foods, the percentage of Americans avoiding gluten in their diets without medically documented sensitivity to gluten tripled between 2009 and 2014. By 2018, 1 in 5 Americans reported gluten avoidance in their diets. While scientific studies have repeatedly shown that a gluten-free diet is therapeutic for people with laboratory-verified celiac disease and wheat allergies—and perhaps for people with non-celiac gluten sensitivity—there is little credible evidence pointing to benefits of such a diet for healthy, gluten-tolerant individuals.

• Gluten is the name for a group of proteins in specific cereal grains—wheat, rye, and barley, as well as hybrids of those crops—that help fuel the growth of developing seedlings.
  • Oats contain gluten-like proteins that are slightly different from the gluten proteins found in wheat and other grains. Because they are different, they do not generally trigger allergic reactions in people who are allergic to wheat gluten and other glutens. But studies have found that oats that are not certified as gluten-free are sometimes contaminated during processing with gluten proteins from other grains.
• Gluten accounts for 75% to 80% of the protein content in wheat and related cereals. Gluten proteins can trigger an immune reaction in sensitive individuals.
• Gluten proteins are common additives to processed food because they are elastic—improving the texture, moisture retention, baking properties, and flavor of foods to which they are added.

Studies estimate that up to 10% of the US population has either a specific immune system reaction to gluten proteins or a less well understood “sensitivity” to gluten-containing products. About 1% of the U.S. population has the specific immune system reaction, which causes celiac disease, dermatitis herpetiformis, and wheat allergy. Less is known about gluten sensitivity (“non-celiac gluten sensitivity” or NCGS).

(Triggered by gluten proteins)

• Celiac disease is a chronic autoimmune disease that primarily targets the small intestine.
• The disease has a strong genetic component, with approximately 95% of patients having inherited a type of immune system cell (bearing either HLA-DQ2 or HLA-DQ8 proteins) that, in the presence of gluten, can trigger an immune reaction damaging to the lining of the small intestine.
• An estimated 40% of the North American population has immune system cells bearing these celiac-associated HLA proteins, but only approximately 1% of the population develops celiac disease, suggesting that other genes and/or environmental triggers are involved.
• Symptoms of celiac disease are highly variable, but the most common include diarrhea, abdominal pain, constipation, anemia, poor growth in children, and various vitamin and mineral deficiencies.
• Another form of celiac disease, called dermatitis herpetiformis, is characterized by the occurrence of an itchy rash, primarily on the limbs and buttocks. Most patients with dermatitis herpetiformis have celiac-associated intestinal symptoms in addition to skin symptoms.
• Currently, the only effective treatment for patients with celiac disease and dermatitis herpetiformis is adherence to a strict gluten-free diet, although drug therapy with dapsone (diaminodiphenyl sulfone) is often used for controlling the skin-related symptoms of dermatitis herpetiformis. The diet prevents further aggravation of celiac disease and has been shown to lead to long-term intestinal healing in the majority of patients.

(Triggered by gluten and/or other proteins in wheat and related cereal grains)

• Wheat allergies are a category of conventional (“IgE-mediated”) food allergies, which occur via separate biological pathways than those responsible for celiac disease.
• Like other food allergies, symptoms of wheat allergy may include: skin rash, itchy eyes and nose, swelling, abdominal pain, respiratory anomalies, and anaphylaxis (constriction of airways, low blood pressure, nausea/vomiting, dizziness) in cases of severe reaction.
• 1 to 1% of children are allergic to wheat, but for reasons still unclear a significant proportion outgrow the condition by adulthood.
• To prevent allergic reactions, patients are put on wheat-elimination diets. In cases of severe reaction from accidental exposure, epinephrine is the treatment of choice.

(NCGS; triggers are uncertain—potentially gluten or other components of wheat and related cereal grains)

• NCGS is characterized by the onset of a spectrum of intestinal and/or other symptoms following the ingestion of gluten-containing cereals—wheat, rye, or barley— in patients who do not have celiac disease or wheat allergy.
• Several studies in the past decade provide evidence supporting a biological basis for NCGS, linked to a compromised intestinal barrier, movement of microbial or dietary components across the intestinal barrier, and immune activation and inflammation.
• Because triggers of NCGS are poorly understood and may include substances other than gluten, some researchers have proposed renaming the condition “non-celiac wheat sensitivity.”
• Some of the potential triggers for NCGS being studied include:
  • Wheat gluten proteins. Several clinical trials suggest that wheat gluten can cause intestinal and other symptoms of NCGS.
  • FODMAPs—Fermentable oligo-, di-, and monosaccharides and polyols—are highly fermentable carbohydrates found in a variety of plants and cereal grains that are poorly absorbed by the intestine.
  • Amylase-Trypsin Inhibitors (ATIs)—proteins found in cereal grains—bind to cells of the immune system that recognize bacteria and can trigger intestinal inflammation. However, clinical evidence for a link between ATIs and NCGS has not been shown yet.
• Symptoms of NCGS include gastrointestinal symptoms—among which bloating, abdominal pain, and diarrhea are most common—as well as such symptoms as fatigue, headache, anxiety, and cognitive difficulties. An estimated 1% to 9% of the U.S. population may suffer from some degree of NCGS, with prevalence uncertain due to the lack of population-based studies and established diagnostic markers. Several studies suggest an overlap between NCGS and irritable bowel syndrome (IBS), with recent research suggesting that a proportion of IBS patients with elevated levels of antibody to gluten may respond to a gluten-free diet.
• The only effective treatment for NCGS is adherence to a diet free of wheat, rye, and barley. It is unclear whether gluten can be safely reintroduced after a patient has been asymptomatic for an extended time.

• A blood test can identify the presence of specific antibodies strongly associated with celiac disease; definitive diagnosis depends upon a tissue biopsy to confirm celiac-disease-specific intestinal damage.
• Wheat allergies are diagnosed by skin-prick tests and blood tests for antibodies to wheat proteins.
• There are no established biological markers to confirm a diagnosis of NCGS. Currently, NCGS is a default diagnosis for patients who report worsening symptoms after eating gluten-rich foods and resolution of those symptoms on a gluten-free diet, but in whom celiac disease and wheat allergy are ruled out.

• Recent studies point to a rising prevalence of celiac disease, independent of the increased attention to the disease and improved diagnostics. The causes for the increase are not clear, but proposed contributors include improved hygiene, specific infectious agents, and changing diet or use of certain therapeutics that can impact the gut microbial population. Data are lacking on changes in prevalence of wheat allergies over time, but one study estimated that overall prevalence of food allergies in children increased 18% between 1997 and 2007. The reasons for this increase are unknown, but higher rates in developed countries suggest that reduced childhood exposure to certain environmental factors may play a role, as may vitamin D deficiency caused by insufficient exposure to sunlight.
• Due in part to the lack of established diagnostic markers, any ongoing change in prevalence of NCGS remains uncertain.

• Wheat: No. According to one analysis, the amount of wheat consumed per person per year in the United States fluctuated over the past century from a high of 220 pounds in 1900 to a low of 110 pounds in 1970, followed by an increase to 146 pounds in 2000 and subsequent decrease to 134 pounds in 2008.
• Gluten: Yes, slightly. According to the U.S. Department of Agriculture’s Agricultural Research Service data, consumption of “vital gluten” in the United States—gluten that is added to processed foods to improve their characteristics—has tripled since 1977. Americans now consume 0.9 pounds per person per year of vital gluten, but this is a small amount compared to the nearly 12 pounds per person per year of gluten directly consumed from wheat, rye, and barley.

• No. Currently, no genetically engineered wheats are commercially available in the United States.
• Average gluten content of U.S. wheat crops hasn’t changed since the 1920s; however, total protein and gluten content can fluctuate 3 to 4 percentage points from year to year based on rainfall and environmental conditions during crop growth.

• The published research record does not currently support claims that a gluten-free diet has health benefits for people without gluten sensitivities (“gluten-tolerant people”).
  • Gluten-tolerant individuals who follow a gluten-free diet have no significant difference in terms of prevalence of metabolic syndrome or cardiovascular disease risk score than the general population consuming gluten.
  • Contrary to popular belief, there is not sufficient evidence to verify that gluten elimination results in weight loss for gluten-tolerant individuals. Some researchers have suggested that self-reported weight loss after removing gluten from the diet is likely due to other general health-conscious behaviors, reduction in carbohydrate consumption, and/or the limited availability of gluten-free foods.

• Some commercially available products processed to be gluten-free may rely on non-nutritious ingredients to achieve certain qualities, resulting in higher levels of fat, cholesterol, sugar, or sodium compared to whole grain products. Some gluten-free foods have also been found to be lower than whole-grain foods in protein, dietary fiber, and healthful micronutrients such as zinc, magnesium, iron, calcium, folate, vitamin B, and vitamin D. However, the growing popularity of gluten-free foods has led to the development of a wide range of gluten-free products, many with positive nutritional profiles.