Avoiding foods that contain gluten—the most common of a group of proteins found in wheat, rye, and barley—is the latest dietary trend sweeping across the nation, with sales of gluten-free foods and beverages predicted to reach $6.6 billion by 2017. The popular press credits gluten-free diets with preventing a variety of health problems caused by intolerance to gluten, including significant negative effects on cognition and mood. But is there a scientific basis for the buzz?
There is definitely strong science behind the need for some people to eat gluten free, although the fad aspect that is associated with the gluten-free diet is troubling, says Alessio Fasano, MD, Di-rector of the Center for Celiac Research at MassGeneral Hospital for Children. Research conducted by Dr. Fasano, a gastroenterologist and expert on gluten-related disorders, suggests that 3 million Americans suffer from celiac disease, an autoimmune disorder related to gluten consumption, and 18 million more experience symptoms caused by another gluten-related disorder, non-celiac gluten sensitivity (NCGS). The majority of individuals with these disorders re-main undiagnosed, even though untreated celiac disease can lead to serious health consequences from malabsorption of nutrients.
Symptoms in both celiac disease and NCGS can include headaches, “foggy mind” and fatigue along with anxiety and depression, says Dr. Fasano. A review of research on NCGS conducted by Dr. Fasano and colleagues and published in the Sept. 26, 2013 issue of the journal Nutrients found that “several studies suggested a relationship between NCGS and neuropsychiatric disorders, particularly autism and schizophrenia.”
“The incidence of gluten-related disorders is rising, especially in industrialized countries,” Dr. Fasano says. “The data suggest that celiac disease has doubled in prevalence every 15 years. And while it was once thought that celiac disease occurs only in childhood, we now know that individuals can consume gluten with no problem for years, and then develop an intolerance in their 50s or 60s or even later.
“It’s possible that the growing toll taken by gluten reactions may be related to an increase in new varieties of wheat and other grains that have been developed to contain higher protein content. Another important factor is that overall we are consuming higher levels of gluten, which is found in many food products today. Heightened awareness about gluten-related disorders has led to increases in diagnosis, as well.”
Reaction to gluten
Dr. Fasano’s research has contributed to a growing understanding among scientists about how gluten causes problems for genetically susceptible individuals. His findings and those of other researchers suggest that even in healthy people, the body is unable to digest a key protein found in gluten, and instead breaks this protein down into peptides. These peptides are too large to be absorbed in a normal manner by the small intestine, and simply move on through the intestinal tract and are excreted.
Dr. Fasano’s research suggests that people with celiac disease overproduce a molecule called zonulin, which causes the small intestine to become porous and leak the peptides into surrounding tissues. These gluten fragments then trigger an autoimmune response that eventu-ally attacks the walls of the small intestine itself, producing the symptoms of celiac disease. If not treated, celiac disease can cause long-term damage to the intestine.
Gluten sensitivity, involves a more immediate immune response in which the immune system, rather than attacking the small intestine, generates an inflammatory response that may affect many areas of the body, including the brain.
Symptoms of celiac disease and gluten sensitivity are similar and can vary greatly from person to person. They include gastrointestinal symptoms such as bloating, abdominal pain, diarrhea, and constipation; osteoporosis, joint pain, leg numbness, and anemia; and nervous system effects.
Gluten and the brain
The effects of gluten reactions on the nervous system and brain may result in symptoms such as brain fog (trouble concentrating, loss of acuity), memory impairment, difficulty finding words, chronic fatigue, headaches, confusion or disorientation, sleep problems, and a higher risk for mood disorders such as depression and anxiety. Although it’s unclear what causes the brain effects associated with gluten intolerance, scientists have developed some theories:
- Deficiencies in key vitamins associated with the inability of the celiac-damaged small intestine to absorb nutrients may impair brain health and functioning.
- A lack of vitamin B-12 in people with celiac disease may lead to inflammation and the eventual destruction of the brain’s glial cells, which function as immune agents.The loss of a large number of these cells—which comprise about 50 percent of the brain’s mass—may be accompanied by the leakage of a key enzyme from inside the cell, which fur-ther stimulates the immune response. These processes are thought to change the physical structure of the brain and negatively affect cellular functioning.
- Gluten fragments may travel to the brain, where they penetrate the blood-brain barrier. Once in the brain, they may interact with brain receptors for key neurotransmitters and disrupt normal brain function, triggering many of the behavioral and neurological changes observed in people with gluten intolerance.
- The immune system identifies gluten fragments as invaders and mounts an attack against them, causing inflammation. Immune cells may travel to the brain, spreading inflammation and triggering a sort of cerebral allergy that ultimately damages brain cells.
Although individuals who are sensitive to gluten are highly responsive to the elimination of gluten from their diets, Dr. Fasano strongly advises against adopting a gluten-free diet on your own, without checking with a medical care provider first.
“You should have a thorough medical examination to rule out other conditions, such as irritable bowel syndrome or other forms of intestinal inflammation,” he says. “What’s more, if you try to go gluten-free on your own, you will eliminate the only means we have to determine whether your gluten problems are associated with celiac disease, non-celiac gluten sensitivity, or perhaps a wheat allergy.”
Celiac disease is diagnosed through a review of symptoms, a series of blood tests that measure your immune response to gluten, and genetic tests looking for specific genes necessary for the de-velopment of celiac disease. If symptoms and tests indicate that you may have celiac disease, en-doscopy and a biopsy of the small intestine are recommended to corroborate the diagnosis, which is further confirmed when a gluten-free diet eliminates your symptoms. There is currently no reliable, evidence-based test for NCGS. Diagnosis is made by ruling out celiac disease, wheat allergy, and other conditions, and confirmed when a gluten-free diet eliminates your symptoms.
“If your primary physician does not seem familiar with gluten intolerance or cannot answer your questions about it, get a second opinion or ask for a referral to a gastroenterologist who is knowledgeable about gluten disorders,” Dr. Fasano advises. “The gluten-free diet must be closely adhered to and monitored. It requires medical supervision, and should not be attempted on your own.”
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