The dietary fibre hypothesis has been based upon pioneering observations of physicians and epidemiologists. They pointed out relationships between diet and chronic diseases such as cardiovascular diseases, diabetes and cancer. Since then, the definition of dietary fibre has been a matter of controversy and today is not fully agreed upon by experts in the field. Most recent definitions encompass all polysaccharides and lignin that resist digestion in the upper gut. Some definitions also include lower molecular weight carbohydrates. Dietary fibres include a wide array of compounds that vary in chemical structures and properties and they might be naturally present in food or incorporated in food to improve nutritional or technological properties. The physicochemical properties of dietary fibre play a key role in the actions on gut function, including fermentation. These properties depend on the source, the processing history of the plant material, as well as the form under which it is ingested. The concept of dietary fibres has stimulated a great deal of research and thrown new insight into the understanding of their metabolic and physiological effects while consumer interest in healthy foods has encouraged technologists in developing enriched food products and new fibre additives as supplements for food. However, there is still a need to bring dietary fibres into more appealing and healthy foods to increase the fibre intake.