The present invention pertains to nutritional and pharmaceutical compositions for treating and preventing cyclooxygenase-2 mediated diseases and to a process for increasing the cyclooxygenase-2 inhibiting activity of a product. In addition thereto, the present invention relates to the use of one ore more milk protein fractions and/or one ore more milk protein preparations for inhibiting the activity of cyclooxygenase-2 (COX-2), in particular for the preparation of a medicament or a functional food for treating and preventing cyclooxygenase-2 mediated diseases. <;??>;The present invention is essentially based on the finding that in particular milk protein fractions bioactive compounds or mixtures providing a COX-2 inhibiting activity are present.