Following an application from Oy Karl Fazer AB, submitted for authorisation of a health claim pursuant to Article 13(5) of Regulation (EC) No 1924/2006 via the Competent Authority of Finland, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to deliver an opinion on the scientific substantiation of a health claim related to high‑fibre sourdough rye bread and a reduction of post-prandial glycaemic responses. The Panel considers that the food, high-fibre sourdough rye bread, and its “comparator”, glucose, are sufficiently characterised in relation to the claimed effect. A reduction of post-prandial glycaemic responses might be a beneficial physiological effect. The Panel notes that in the four human intervention studies submitted as pertinent to the health claim the consumption of high-fibre sourdough rye bread induced a significant reduction of post-prandial blood glucose responses when compared with glucose. The Panel also notes that, when comparable amounts of available carbohydrates from different carbohydrate-containing foods are tested, almost any carbohydrate-containing food would induce a reduction of post-prandial blood glucose responses compared with glucose. In addition, foods containing low amounts of, or no available carbohydrates, will also induce lower post-prandial blood glucose responses when compared with glucose. The Panel concludes that a cause and effect relationship has been established between the consumption of almost any food and a reduction of post-prandial blood glucose responses as compared with glucose. However, the Panel considers that solid foods, including high-fibre sourdough rye bread, are generally not considered as an alternative to glucose solutions. In this context, conditions of use cannot be established for this health claim.