Study as a proof of principles “Why did you go to Kenya with cassava?” asked a Ghanian early career scientist from the audience during discussion, regarding a study about introduction of high β-carotene containing yellow cassava in Kenya. In fact, the Vitamin A deficiency of the population in Ghana would be much higher than in Kenya, he adds. The presenter from Wageningen University in Holland, Alida Melses responses: “The study is a proof of principle – it doesn’t matter where you work as long as you demonstrate that it works. The area was chosen by practical reasons.” Alida Melse-Boonstra, Wageningen University, Netherlands, about improving nutrition through staple foods in Africa