Gluten-free diet
A gluten-free diet is a diet completely free of ingredients derived from gluten-containing cereals: wheat (including Kamut and spelt), barley, rye, oats and triticale.  Although most patients can tolerate oat products, there is a controversy about including them in a gluten-free diet: some medical practitioners say they may be permitted, but the Coeliac Society advises against them.

# Gluten-free food
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.
People wishing to follow a completely gluten free diet must also take into consideration the ingredients of any over-the-counter or prescription medications and vitamins.  Also, cosmetics such as lipstick, lip balms, and chapsticks may contain gluten and need to be investigated before use.

## Cross-Contamination Issues
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), malt flavoring, and glucose syrup. Many common ingredients contain wheat or barley derivatives.  Maltodextrin, formerly thought to contain gluten, is generally considered gluten free.  
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.

### Controversy over Oats
The suitability of oats in the gluten-free diet is still somewhat controversial. Some research suggests that oats in themselves are gluten free, but that they are virtually always contaminated by other grains during distribution or processing. However, recent research indicated that a protein naturally found in oats (avenin) possessed peptide sequences closely resembling wheat gluten and caused mucosal inflammation in significant numbers of coeliac disease sufferers. Some examination results show that oats are very dangerous to certain celiacs, while not very harmful to others. Given such conflicting results, excluding oats is the only risk free choice for coeliac disease sufferers.
The cross-contamination issue with oats, can also be inferred to extend to all other grains that share the same farm, truck, mill, or bagging facility as wheat and other gluten-containing grains.   Therefore, removing all flours and grains from the diet may be the only way to guarantee a complete absence of gluten in the diet.

## Accuracy of "Gluten-Free" Labels
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).
Australian standards reserve the "gluten free" label for foods with less than 5 parts per million of gluten, as this is the smallest amount currently detectable. As gluten-containing grains are processed, more and more of the gluten is removed from them, as shown in this simple processing flow:
Wheat Flour (80,000ppm)  >  Wheat Starch (200ppm)  >  Dextrin  >  Maltodextrin  >  Glucose Syrup (  Dextrose  >  Caramel Color
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 (especially Australia and the European Union) new product labelling standards are enforcing the labelling of gluten-containing ingredients. Various gluten-free bakery and pasta products are available from specialty retailers.
Unfortunately, in the United States, the Food and Drug Administration (FDA) has not yet defined the term gluten free as it appears on food labels.  It is currently up to the manufacturers of "gluten free" food items to guarantee such a claim. "A final rule that defines the term gluten-free and identifies the criteria that would enable the food industry to use that term" is scheduled to be released by the FDA on August 2nd, 2008  	 
. Many so-called gluten free products have been found to have been contaminated with gluten (such as Pamela's cookies 	 
, etc.).

## Alcoholic Beverages
Almost all beers are brewed with barley (and sometimes wheat), and hence are unsafe for the gluten-avoider to drink. Sorghum and buckwheat based beers are available, but remain very much a specialty product.  Most specialists now consider all distilled forms of alcohol safe to drink, provided no colourings or other additives have been added, as they might include gluten ingredients.  Wine, sherry, port, cider, rum, tequila, bourbon and vermouth are all probably safe. Liqueurs and pre-mixed drinks should be examined carefully for gluten-derived ingredients. Some gluten free beers are available.

### Gluten-Free Beer
There is a disagreement over the use of gluten products in gluten-free brewed beverages. Some brewers argue that the proteins from such grains as barley or wheat are converted into amino acids during the brewing process, and therefore gluten-free. They claim that beers brewed mainly  from grains such as rice, sorghum, buckwheat, and maize (considered safe for celiacs) but including some barley or wheat, are still safe. However, there is evidence that this claim is false . Brewers who produce low gluten beers are required to test every batch for gluten, recorded in "parts per million" ('ppm'); gluten levels in these brews are still evident, showing that gluten does survive the brewing process.
Gluten-free brewers and those concerned with coeliacs or conditions that require a gluten-free diet, tend to be explicit that beer brewed using wheat or barley is unsuitable for those with coeliac disease or dermatitis herpetiformis. 
   But particular malt brews of England and Finland with carefully controlled gluten levels may be low enough to be consumed in relative safety (Against the Grain, 13ppm; Koff, 20ppm; Laitilan, 4ppm).  Conflicting this assumption is a school of thought that all testing is unreliable for hordein,   therefore, only brews developed from gluten-free ingredients are safe for all persons with a gluten intolerance.
It is likely that most coeliacs will be able to drink beer at under 20 ppm (in moderation) without causing themselves any harm; however, each person has a different level at which an autoimmune response will be activated and there is some debate over the gluten level acceptable to coeliacs. 
It is advised that consumers of all "low gluten" foods and beverages tell their consultant about the brewed beverages they consume to ensure that even if the obvious symptoms are absent, there are no other negative effects they need to be aware of. Some large scale commercial brewers suggest that their beers may not be dangerous to coeliacs, but the evidence does not support this and these beverages pose a risk to coeliacs who want to rationalize that they can continue to be exposed to normal beverages. 
Notwithstanding this advice, the recent development of gluten-free ales, lagers,  and beers has been a very positive move to liberate those who suffer a variety of related conditions from possible social isolation; and there is an entire grass-roots movement of people working to produce flavorful gluten-free beer,   just as improvements in gluten-free bread and pasta now make it possible to consume foods that are acceptable in flavour and texture without any wheat or gluten component.
In November 2006, Lakefront Brewery of Milwaukee, Wisconsin launched its "New Grist" gluten-free beer, brewed with sorghum and rice.  It is one of its most successful lines. New Grist is aimed at those with celiac disease,  although its low-carb content also makes it popular with diet-minded drinkers. 
In December of 2006 Anheuser-Busch began selling Redbridge, a sorghum-based, gluten-free beer. 
In many ways beer seems to be the hardest gluten-free product to "get right". However, gluten-free beer is becoming increasingly available, and there are now a range of ales, beers,  and lagers to choose from. Dr Steve Ford (of www.glutenfreebeerfestival.com, the international resource for gluten-free beer,)   divides the market into two types: "no gluten" and "low gluten". The glutenfreebeerfestival aims to promote choice, "to choose a beer, if that is wanted, and to allow the coeliac to have a choice of (a) brew that they may wish to consume."
Consideration of brewed beverages in a gluten-free diet is advantageous to persons with Celiacs Disease because a gluten-free diet helps prevent the development of future health problems with consequences possibly as debilitating as diabetes.

# Medical Benefits
The gluten-free diet must be strictly followed by sufferers of celiac disease and dermatitis herpetiformis. Some medical practitioners also believe the diet may be helpful for persons with multiple sclerosis and other autoimmune disorders, as well as autism spectrum disorders, ADHD, and some behavioural problems.
The scientific literature on the link between gluten and autism is mixed and there is no substantial research on in utero causality.  One study examined the effect of a strict casein-free and gluten-free diet on children with autism. The experimental group were fed the diet for 12 months. During that period the children had significantly fewer autistic symptoms than the control children, who were not fed the diet.
On the other hand, other studies have not found the same results.  For the most recent review of scientific literature on the link between autism and a gluten-free diet, please see the article "Elimination diets in autism spectrum disorders: any wheat amidst the chaff?"