Gluten (=gliadin + glutenin) is a protein that is present in cereals like wheat, barley, rye, oats et cetera. It is responsible for the elasticity of the doughs made of these cereals.. Gluten forms an important source of protein in human diets.

However, an increasingly large number of people in the US and the world, are diagnosed with a condition called Gluten Intolerance (Coeliac/Celiac disease in medical parlance). In common terms, it is an allergic reaction to gluten, with symptoms like

• bloated feeling
  
• vomiting
• diarrhoea
• fatigue
• weight-loss
• et cetera

Gluten-free is a label given to any product that contains no gluten (less than 200 ppm). A gluten-free diet is one that contains no wheat, barley, oats or rye, and is one which is mandatory for life, for patients of gluten intolerance.

To substitute for the loss of nutrition, other components like potatoes, maize, rice, sorghum, millet and yam among others are used.

Several products are available in the market which have the "gluten-free" label, making life easier for people these days, like Granola Bars for instance.