The present invention relates to the treatment or prevention of conditions linked to reduced muscle mass or reduced muscle protein synthesis rate. A subject matter of the invention is a composition comprising complexes of whey protein micelles and pectin for use in the treatment or prevention of a condition selected from the group consisting of sarcopenia, muscle atrophy and negative nitrogen balance. Further aspects of the invention relate to the non-therapeutic use of a composition comprising complexes of whey protein micelles and pectin and a food composition.