The Health Claims Regulation entered into force in January 2007. The European Food Safety Authority (EFSA) has evaluated more than 3000 health claims since then, but EFSA's responsibilities in this area and the extent to which its scientific assessments are in accordance with the current legal framework are still not fully understood.The scope of this paper is to provide insight on the use of scientific knowledge in the area of nutrition for the substantiation of health claims made on food. The reasons why a positive evaluation by EFSA may not be sufficient for the authorisation of a health claim are also discussed. Concrete examples are used to illustrate these aspects.How health claims are scientifically assessed by EFSA has not been fully understood by stakeholders yet. Thorough knowledge on how EU legislation translates into scientific requirements for substantiation is essential to building successful applications. Other factors which may play a role in the authorisation of a claim and which are not evaluated by EFSA, such as the legal status of the food/constituent, its safety, or the compatibility of the claim with national and international dietary recommendations, should also be considered early in the process. EFSA is committed to providing further guidance to stakeholders on how to prepare applications for authorisation by making use of its 10 years of experience on the scientific evaluation of health claims made on food.