Gluten is a naturally occurring protein found in grains in varying concentrations - specifically wheat, oats, rye, and barley (but not rice). Some people can develop a hyper-sensitivity to the protein called Coeliac disease. This is a recognised auto-immune disease that causes severe and potentially deadly gastrointestinal problems. Ingestion of even tiny amounts of Gluten can cause severe and immediate reactions in sufferers. At the end of the 20th Century, Non-Coeliac Gluten Sensitivity (NCGS) was defined for people who seemed to have similar (though milder) symptoms of coeliac disease but who were not diagnosed as such. The diagnosis remains controversial and is not widely recognised in the medical community. On top of this Gluten has become the go-to cause for many other gastrointestinal ailments such as IBS and many sufferers are self-diagnosed, creating a dietary fad element to its ingestion.
For many years the only gluten-free foods available in the UK were through chemists and supplied on prescription. The taste and texture were also very poor. Coeliacs had to manage a minefield of careful cooking and purchasing food to ensure their exposure was minimised. Because gluten is found in grain and these grains are ubiquitous in Western cooking - used in most processed and restaurant meals - it made managing that exposure problematic. In the last few years however, because of the increase in people wanting to remove gluten in their diet (regardless of whether it is necessary) the availability and quality of gluten-free products has improved hugely.
This has been of benefit to genuine coeliac sufferers who can now purchase and consume a wide range of foodstuffs previously denied to them.