A gluten-free diet is a diet completely free of ingredients derived from gluten-containing cereals: wheat, barley, rye, kamut, spelt, and triticale. The suitability of oats in the gluten-free diet is uncertain; consequently most persons who have been medically directed to follow a gluten-free diet also avoid oats. This diet must be strictly followed by sufferers of celiac disease and dermatitis herpetiformis. Some medical practitioners also believe the gluten-free diet may be helpful for persons with multiple sclerosis and other autoimmune disorders, but this has not yet been conclusively proven through medical studies.
Several grains and starch sources are considered acceptable for a gluten-free diet. The most frequently used are maize (corn), potatoes, rice, and tapioca (derived from cassava). Other grains and starch sources generally considered suitable for gluten-free diets include amaranth, arrowroot, millet, montina, lupine, quinoa, sorghum (jowar), sweet potato, taro, teff, and yam. Various types of bean, soybean, and nut flours are sometimes used in gluten-free products to add protein and dietary fiber. In spite of its name, buckwheat is not related to wheat; pure buckwheat is considered acceptable for a gluten-free diet, although many commercial buckwheat products are actually mixtures of wheat and buckwheat flours, and thus not acceptable.
Special care must be taken when checking ingredients lists as gluten may come in forms such as vegetable proteins and starch, modified food starch (when derived from wheat instead of maize), maltodextrin, malt flavoring, and glucose syrup. Many common ingredients contain wheat or barley derivatives.
Many foods will contain gluten, but not be indicated on the ingredients, because they are not in the formulation of the product, but in the preparation of it. One example of this is the dusting of the conveyor belts in the production facilities to prevent the foods from sticking during processing. The food itself might not contain gluten, but there is gluten in the ingested product.
The legal definition of the phrase "gluten-free" varies from country to country. Current research suggests that for persons with celiac disease the maximum safe level of gluten in a finished product is probably less than 0.02% (200 parts per million) and possibly as little as 0.002% (20 parts per million). Since ordinary wheat flour contains approximately 12% gluten, even a tiny amount of wheat flour can cross-contaminate a gluten-free product. Therefore, considerable care must be taken to prevent cross-contamination in both commercial and home food preparation.
This diet rules out all ordinary breads, pastas, and many convenience foods. Many countries do not require labelling of gluten containing products, but in several countries new product labelling standards are enforcing the labelling of gluten-containing ingredients. Various gluten-free bakery and pasta products are available from specialty retailers.
Alcohol and the gluten-free diet
Almost all beers are brewed with barley (and sometimes wheat), and hence are unsafe for the gluten-avoider to drink. Sorghum beers are available, but remain very much a speciality product. Doctors have advised people in the past to avoid whisky, grain vodkas and gin, as they are made from gluten-containing cereals. However, more recent research shows that the distillation process leaves behind the offending prolamins and render the drinks safe. Most doctors now consider all distilled forms of alcohol safe to drink.  Wine, sherry, port, cider, rum, tequila, bourbon and vermouth are all safe. Liquers and pre-mixed drinks should be examined carefully for gluten-derived ingredients.
Gluten free, casein free diets and autism
Many parents of children with autism have reported that a gluten-free casein-free diet helps their children. According to the theory, some children are unable to digest the protein in many cereals (gluten) or in milk (casein) completely.
The molecular structure of the partially undigested proteins, known as peptides, resemble opiates. It is thought that such peptides have an effect much like opiates in the brain and nervous system. From this premise it follows that long term exposure to these opiate peptides can have many damaging effects on the developing brain and also affects behavior, just as any narcotic would.
The opioid peptides involved are identified as casomorphines from casein, and gluten exorphines and gliadorphin from gluten.
Many parents report that removing casein and gluten from their child's diet increases eye contact, attention span, and general mood while decreasing problems like tantrums, self-stimulatory behavior (such as hand-flapping and rocking) and aggression. Many find that providing a diet free of casein and gluten aids children in successfully learning daily living skills like dressing, using the toilet as well as improving coordination and imaginative play activities. In a small number of cases, such dietary changes have resulted in dramatic improvements, enabling the child to attend mainstream educational programs in a matter of months.
Beginning the diet can be difficult but not impossible. Gluten is most commonly found in wheat, rye, and barley and may sometimes contaminate oats grown nearby or processed on the same equipment as gluten-containing cereals, and casein is found in dairy products; wheat and dairy frequently make up a large proportion of the Western diet. One of the biggest obstacles parents face is that individuals needing gluten-free, casein-free (GFCF) diets often crave these foods much the same as an addict. In fact, parents often report withdrawal symptoms when gluten and casein are eliminated that are similar to addicts experiencing withdrawal from narcotic drugs.
Many parents worry about removing wheat and dairy because these foods are the only ones their child will eat, and because prevailing attitudes in Western culture consider them an essential staple. However, children who eat only or mostly wheat and dairy products often show remarkable improvement once a GFCF diet is underway. Many families have found from experience that their children's menu options actually increase after the effects of eating gluten and casein have subsided.
Some people experience immediate improvement although it may take as long as six months for gluten to clear out of the system and one month for casein to clear. Advocates of the diet recommend trying it for at least a year as it can take this long for some children to show improvement. The diet affects changes in the body at a cellular level and promotes healing of the stomach and intestinal lining, both of which can take time.
Although this diet has been questioned by the medical community, many doctors and university research centers are advocating the use of this intervention for autistic children, especially after seeing results first-hand. Doctors who work with DAN! (Defeat Autism Now) are supportive of interventions such as the GFCF diet.
Although food sensitivites have been known about for decades they are rarely given consideration in diagnosis, therapy and recovery efforts. The specifics of the GFCF diet were introduced to the general public through the combined publications of two women who researched interventions and crusaded for autism recovery. Information about the GFCF diet has since spread around the world and has helped thousands of families cope with this puzzling disorder.
The GFCF diet has been supplemented with a number of new innovations. These include incorporation of the Feingold diet, the Specific Carbohydrate Diet, diets with reduced salicylates and phenols, etc.
There are as yet few studies that prove or disprove the GFCF diet or other diets, but there is growing acceptance in the medical community that restrictive diets affect pediatric and adolescent behavior.
Those who are suffering from celiac disease and/or dermatitis herpetiformis are instructed to avoid all forms of gluten, though their metabolic disorders are different from those with autism. There are anecdotal reports of this diet also being beneficial to sufferers of multiple sclerosis, schizophrenia, Tourette's syndrome, chronic fatigue syndrome and attention deficit disorder.