Landlocked Niger on the southern edge of the Sahara Desert is one of the poorest countries in the world, and less than a third of its population have access to any health care. Malnutrition remains the main cause of maternal and infant mortality: there's a hidden hunger among almost all the women and young children, caused by iron-deficiency anaemia. It's an unseen problem, that slowly steals away the body's strength and immunity to disease.