In his book Food security and scarcity, Harvard academic and Center for Global Development fellow Peter Timmer says global hunger eradication is so hard “because governments and markets need to work together around an agenda of pro-poor growth, agricultural development, and stable food economies”.  (See below for a video of Timmer discussing how agriculture meshes with broader structural economic changes in the developing world.)
Per Pinstrup-Andersen, an economist at Cornell University in the United States, has edited a complementary volume, Food price policy in an era of market instability.  This is written in the context of the food price volatility seen worldwide since 2007. The book is mainly based on 14 case studies from developing countries. It shows how government responses either amplify or address the issue.
Both books draw out several interesting policy lessons and make clear that scientific research is only one element among many needed to improve people’s diets.
Let’s take the Pinstrup-Andersen book. He writes, among other things, of the need to strengthen the “policy-relevant evidence base”, to reduce the “fiscal costs of short-term interventions” such as subsidising food and fertilisers, and investing in “improved rural infrastructure”. (Pinstrup-Anderson summarises these and other issues in a handy policy brief.) 
The attentive reader will be surprised how minor a role agricultural research and science plays in both books.
Returning to Africa: this should not be that surprising, since its agricultural practices are different from those in Asia, where nutritional improvements have been comparatively easy to achieve. The high and reliable yields of the rice varieties championed by the International Rice Research Institute over its 50-year history ensured that Asian countries increased supply dramatically. Noting this, Timmer contrasts his visits to Karawang in West Java, Indonesia, and the Machakos region of Kenya. While Karawang has extensive and well irrigated rice fields, Machakos has poor roads, a dependence on rainfall and small farms that grow multiple crops next to each other. There are maize, sorghum, millet, cassava, yams, groundnuts, cowpeas and many other crops.
For such reasons, a Green Revolution for Africa is much more challenging. It is not only a question of developing new and better varieties of crops, but also of ensuring that these fit into a highly complex agricultural and economic system.
So it is hard to say in general whether Africa’s diet will improve soon. You only need to check the country-by-country studies released this month by the Global Nutrition Report to see how complex the situation is. 
Too much of Africa’s growth depends on exporting minerals, oil and natural gas. Many countries certainly need a more productive agricultural sector, where agricultural research and food policy both play a role. Without generating a surplus or costly food imports, the cities cannot be fed. But it is not just a question of increasing agricultural productivity. Other factors, such as better employment for those in the informal sector, are needed to provide the inclusive growth and poverty eradication that will improve diets more widely.
Roger Williamson is an independent consultant and visiting fellow with both UNU-WIDER and the Institute of Development Studies at the University of Sussex, United Kingdom. Previous positions include organising nearly 80 international policy conferences for the UK Foreign Office and being head of policy and campaigns at Christian Aid.
References David Leonhardt As Africa prospers, will diets improve? (New Telegraph, 16 February 2015)
 Suzanne Goldenberg Lester Brown: ‘Vast dust bowls threaten tens of millions with hunger’ (The Guardian, 25 February 2015)
 C. Peter Timmer Food security and scarcity: Why ending hunger is so hard (Penn Press, 2015)
 Food price policy in an era of market instability (Oxford University Press, November 2014)
 Per Pinstrup-Andersen How do governments respond to food price volatility? (UNU-WIDER, January 2015)
 Actions and accountabilities to accelerate the world’s progress on nutrition (International Food Policy Research Institute)