Interventions in complex systems cause unintended consequences: The WHO set the ambitious goal to eliminate anemia among young women in Africa by providing iron supplements. However, they had to stop the study when it became clear that the intervention actually increased the rate of hospitalisations and death. Malaria turned out to be the cause for this. The parasite P. falciparum infects red blood cells and digests hemoglobin that is rich in iron. Having iron deficiency has a protective effect against Malaria.