The study population consists of children judged to be in complete clinical remission from cancer. In a phase 1 trial, one usually uses healthy individuals as study subjects, but in pediatric studies this is not allowed. Therefore patients who are in full remission were chosen as study objects, but who still come to the clinic for regular follow-ups. This group of patients is relevant for this study since it represents all ages and base-line diets, all kinds of childhood cancers, and because they have suffered from cancer and in many cases still live with the severe consequences of it.