The number of chronically hungry people currently hovers just below the one billion mark, according to FAO. That figure, however, hides an even greater problem. Roughly two billion people, most of them women and young children, suffer malnutrition associated with a lack of micronutrients and vitamins. Furthermore, so-called diseases of affluence, such as type-2 diabetes, cardiovascular disease, obesity and cancers are increasing most rapidly in developing countries. The underlying reason for both of these observations is that diets have become simpler. The prevailing highly medicalised view of micronutrient deficiency sees only supplements and biofortification as effective treatments. Neither approach, however, often does not reach the poorest sectors of society where they are most needed. Similarly, while developed country governments exhort citizens to eat a greater diversity of fruit and vegetables for their health, such policies do not appear to be common in developing countries. Agricultural biodiversity offers an alternative approach to malnutrition and health, with additional important benefits for productivity, environmental sustainability and human and economic development. Examples will be presented of research to make greater use of agricultural biodiversity to increase dietary diversity, often using local diversity and addressing agronomic, social, marketing and other constraints. Much current agricultural research for development is focused on increasing major nutrients, such as protein and carbohydrate, at the expense of micronutrients. It will be argued that better nutrition and health would be just one outcome of more research into the wider use of agricultural biodiversity.