Gluten-free refers to a diet that excludes sources of gluten, a protein found in wheat, barley, spelt, kamut, rye and derivatives thereof such as flour, malt extract, wheat starch etc. Gluten gives bread its elasticity and shape, and is used as a stabilizing agent in other foods.
The gluten-free diet can be adopted as a treatment for legitimate medical conditions, most notably celiac disease, but it has also been embraced as a fad diet, weight-loss gimmick, and purported autism cure.
 Reasons for adoption
While the diet is used to treat celiac disease and related disorders, some people adopt a gluten-free diet for a different imagined health benefit. Because of the constraints the diet imposes, doing so may be detrimental to their health.
 Celiac disease
Celiac disease (or coeliac outside of the US) is an autoimmune disorder which interferes with digestion. The immune system responds to gluten peptides absorbed in the small intestine, causing inflammation and damage to the gut and a variety of unpleasant symptoms. There are also long-term effects primarily related to malabsorption, including failure to thrive (in children), chronic diarrhoea and digestive problems, osteoporosis, anaemia (generally iron, vitamin D and folic acid), a characteristic form of blistering eczema and a small increase in risk of cancer. Even a small amount of gluten (e.g. a small crumb or dusting of flour) can trigger an attack. Symptoms of being "glutened" range from person to person but typically include lethargy, nausea, vomiting, and diarrhea.
The condition has been recognized since at least the first century CE, and was described by Aretaeus of Cappadocia (the name itself is of ancient Greek origin). Greater understanding and research has only occurred more recently; the link with wheat was not definitively made until 1940. Like autism, this has led some people to think that celiac is a modern disease. The reality is that even ancient forms of wheat such as spelt and kamut trigger an attack as easily as any modern wheat variety. It is more likely that better recognition of the symptoms accounts for the higher rates of diagnosis. It is still widely considered to be under-diagnosed with an estimated prevalence in the population as high as one percent.
It is not possible to self-diagnose celiac disease, not least because the symptoms are generally indistinguishable from conditions such as irritable bowel syndrome (IBS). Diagnosis normally consists of a blood test followed by a duodenal biopsy that examines the intestine lining for villous atrophy (erosion of the villi, structures which increase the surface area of the gut wall to improve absorption). In extreme cases the gut wall may become completely smooth. The blood test is very accurate with a false negative rate of less than 5% and a much lower false positive rate, leading some specialists to dispute the need for a (mildly distressing) biopsy in clear-cut cases.
The only current proven treatment is a completely gluten-free diet which allows the intestine to heal, absorb nutrients and function normally. However, there are some early vaccine trials that are attempting to desensitize the body's immune response to gluten peptides. There has also been some preliminary evidence that Helminthic therapy might be an effective treatment.
 Wheat allergy or gluten sensitivity
Aside from celiac disease, many people have a less-intense but still real sensitivity to gluten. Levels of sensitivity can vary from person to person. Still other people have a wheat allergy, which is not the same as celiac disease or gluten sensitivity. Because of the lifestyle changes a gluten-free diet imposes, and because advanced cases of celiac sometimes need additional immunosuppressant or steroid treatments, it's important to be examined by a competent medical professional when someone has concerns about their intake of gluten.
Not all sensitivites to gluten are real, though.
A correlation exists between patients suffering from autoimmune hypothyroidism and celiac disease. This association is on the order of a tenfold increase in the odds of having celiac disease if you have Hashimoto's thyroiditis, as compared with the incidence of celiac disease in the general population. One possible mechanism is a similarity between gliadin, a protein component of gluten, and one or more thyroid tissues.
This, of course, leads to inevitable overreaction, such as claiming that all hypothyroid patients should go gluten-free.
 Autism quackery
Gluten-free diets are sometimes promoted by anti-vaccination types such as Jenny McCarthy as a means to treat or "cure" autism. There is no known basis for this assertion, and in fact a gluten-free diet can make you worse off if you aren't somehow making up for lost nutrients.
A study presented at the International Meeting for Autism Research showed that 18% of children with autism, Asperger disorder, or PDD-NOS had been put on a "special diet" advocated by alternative medicine, and among those, 47-50% had been put on a gluten-free diet. Families discontinued the use of special diets at a rate of only 5-10% per year, indicating a strong adherence to the idea despite a lack of results.
 Weight loss quackery
Diet woo for weight loss has jumped on this one! Here is the reason you're fat: it's gluten. Few medical experts or professional dieticians have ever found any reason to suggest a gluten-free diet aids in weight loss, but seemingly it fits so well into the "low-carb" "paleo diet" world. Early in the trend, going "gluten-free" was likely to lead to weight loss, because it necessarily cut out a number of foods which are calorie dense, such as pastas, breads, and other baked goods. However, since the trend has grown, it is now easy to find gluten free varieties of these items, as well as a large number of gluten-free junk food items, thus making it just as easy to be obese without gluten as it is with.
 The gluten-free lifestyle
The gluten-free diet is moderately tiresome to stick with and unless you are medically required to you probably shouldn't bother.
If you have a partner who is highly sensitive to cross-contamination, you may end up on a gluten-free diet yourself, depending on their sensitivity. Learn to love rice pasta, millet bread, and sorghum beer. Wine, cider, and distilled alcoholic beverages are safe too.
 Safe and unsafe foods
At its most basic, the diet means cutting out any source of gluten, primarily wheat, barley and rye. Kamut and spelt are "ancient" forms of wheat that still contain gluten.
The most obvious sources of gluten would be bread, biscuits and some cakes. But many foods have unexpected gluten. Wheat flour is often used as a thickener and starch, meaning that most restaurant soups and many sauces will contain gluten. Pseudo grains such as millet, buckwheat, quinoa are fine, as are potatoes, rice and corn. Oats are frequently contaminated due to being processed on machinery also used to process wheat, but there are brands which are tested and certified free from contamination. Wheat gluten is often used in meat substitutes, and sausages may contain biscuit rusk. For those with celiac, cross-contamination in the manufacturing process can also be a source of hidden gluten so it's important to check packaging for shared equipment warnings.
Some foods or food ingredients, like monosodium glutamate or "glutinous rice", are safe (or at any rate, gluten-free) despite their similar names.
Highly processed grain derived products such as maltodextrin, grain alcohol (yay) and malt vinegar are usually gluten free. Some gluten free products will use highly processed wheat starch which is also gluten free.
In short it is vital to inspect the ingredients extremely carefully and if in any doubt, don't buy. It is common to find that one brand of a product (e.g. ketchup) is safe while another brand is not.
 Gluten-free alternatives
Many gluten-free substitute foods are available, such as bread and pasta made from rice & corn flour; some products also use balsa wood and styrofoam, or at least taste as if they do. The quality of bread varies widely based on the ingredients and preparation involved. The biggest problem is that bread tends to fall or part or squash because it is not elastic. Some gluten free mixes use additives to preserve the shelf life of the product, with cellulose being a common ingredient.
Grocery shopping outlets such as QFC and Fred Meyer, and home-delivery services such as Amazon Fresh, have special sections for gluten-free foods. Many restaurants have a gluten-free alternate menu, or mark gluten-free items on the menu itself or in a nutrition guide.
Coeliac UK has a website with an online food database that includes many supermarket brands, and UK residents can also get gluten free staples on prescription through the NHS. The additional cost of gluten free foods is tax-deductible for US residents with a true coeliac diagnosis (as opposed to "thinking that gluten is bad for them").
 Food regulation
A danger to genuine celiacs is that if gluten-free is perceived as a "lifestyle" choice then many food preparers may not educate themselves or treat the condition with the seriousness that it deserves, e.g. not bothering to prepare food separate from sources of contamination that won't harm people on some GF fad diet but can cause serious harm to a celiac sufferer. Because of this, gluten-free labeling is regulated in many parts of the world.
Europe has instituted new regulations (based on the Codex Alimentarius standards) that require food advertised as gluten free to possess less than 20 parts per million (ppm) of gluten. A second category of food possessing less than 100ppm may be advertised as very low gluten.  Some products may be "naturally gluten free" which means there is nothing to imply gluten (e.g. a bag of carrots is naturally gluten free) but no formal testing has been done to know for sure and in the case of some grains occasional contamination does occur. Many products also show a gluten free symbol of some kind (usually a wheat ear with a red line through it) but not all of them. Most products are required to list allergens but if wheat is listed in the ingredients it might not be listed separately in the allergens box. To the consternation of many celiacs, labelling and packaging is still notoriously vague and variable.
 See also
- Gluten Free Certification Organization
- Celiac disease
- Diagnosis of gluten sensitivity
- Gluten-free children's play sand -- no, really!
- ↑ WebMD: The Truth About Gluten
- ↑ The Extant works of Aretaeus, the Cappadocian.
- ↑ Coeliac prevalence and screening, Coeliac UK
- ↑ WebMD: Celiac Disease - Topic Overview
- ↑ Pioneer in the gluten free diet: Willem-Karel Dicke 1905-1962, over 50 years of gluten free diet
- ↑ Nexvax2® – Lead therapeutic
- ↑ ... or is it? Does gluten sensitivity in the absence of coeliac disease exist?, Imran Aziz et al., British Medical Journal, 30-Nov-2012
- ↑ What if your gluten intolerance is all in your head?, New Scientist, 11-July-2013
- ↑ e.g. Chris Kresser (a licensed acupuncturist and practitioner of integrative medicine), The Gluten-Thyroid Connection
- ↑ The GFCF (Gluten-Free, Casein-Free) Diet for Autism Spectrum Disorders
- ↑ GlutenFreeHelp.info: Louder Than Words by Jenny McCarthy
- ↑ WebMD: Gluten-Free/Casein-Free Diets for Autism
- ↑ ABC News: A Gluten-Free, Casein-Free Diet No Remedy for Autism
- ↑ Evaluation, Diagnosis, and Treatment of Gastrointestinal Disorders in Individuals With ASDs: A Consensus Report
- ↑ INSAR: Persistence of Complementary and Alternative Medicine (CAM) Use In ASD
- ↑ example
- ↑ SparkPeople: Celiac Disease and Gluten Free Group
- ↑ Weight Watchers: Gluten-Free Main Dishes
- ↑ Kill me now. -- PintofStout
- ↑ WebMD: Hidden Gluten - Topic Overview
- ↑ Celiac.com's list of safe ingredients
- ↑ Udi's Gluten Free Bread
- ↑ QFC: Gluten Free
- ↑ Amazon: Learn How to Shop for Gluten Free
- ↑ concerning the composition and labelling of foodstuffs suitable for people intolerant to gluten