Gluten is a protein in wheat, rye, and barley that is commonly found in bread, beer, pasta, and a wide range of other processed foods containing these grains.
For about 1% of the population, eating gluten causes coeliac disease. This is an autoimmune disease in small intestine. It involves an immune reaction to gliadin (a gluten protein), found in wheat, barley, rye and some oats. Coeliac disease can present with malabsorption, chronic diarrhoea, weight loss, fatigue, bloating and anaemia. In coeliac disease sufferers, avoiding gluten can be lifesaving, as ongoing exposure to gluten can cause anaemia, weight loss or even bowel cancer in these patients.
A further 1-2% of the population may suffer from a true wheat allergy. A true wheat allergy can cause symptoms such as hives, swelling, abdominal pains, vomiting or even wheezing shortly after exposure to wheat. People with a suspected wheat allergy should be assessed by an allergist, and if the wheat allergy is confirmed, should avoid all components of wheat including gluten.
However, in the remaining 96-98% of the population, there is very little scientific evidence to support a gluten-free diet. Nonetheless, gluten-free has become a trend: 15% of Britons and 25% of Americans are attempting a gluten-free diet. It has become a multi-million dollar industry.
Gluten has been blamed for a wide variety of symptoms including headaches, weight gain and ADHD, but there is little scientific backing to support this.