In projects concerning big data, ethical questions need to be answered during the design process. In this paper the Value Sensitive Design method is applied in the context of data-driven health services aimed at disease prevention. It shows how Value Sensitive Design, with the use of a moral dialogue and an ethical matrix, can support the identifcation and operationalization of moral values that are at stake in the design of such services. It also shows that using this method can support meeting the requirements of the General Data Protection Regulation.