‘The Great Protein Fiasco’, from the title of a 1974 paper in The Lancet by Donald Mclaren, is the name given to the period in international development policy from the late 1950s until the early 1970s. Throughout this time, UN agencies including the WHO and FAO, national aid programmes and famine relief charities pursued policies which put a particular focus on protein, overseeing the development of novel, high-protein foods, and prioritising access to protein sources in delivering food aid. This policy consensus was motivated by three generally accepted beliefs: that kwashiorkor was the leading cause of child mortality around the world and was caused by specific protein malnutrition (see kwashiorkor); and that the world faced a ‘protein gap’, or was bound to do so as population increased (see the Protein Gap). All three of these assumptions were moderated or completely undermined as better evidence came to light, but even so it took some time for the policy consensus to change. In using the word ‘fiasco’ to describe his era, Mclaren was levelling the charge that a huge amount of time, energy and money had been wasted on narrowly protein-focused, technocratic solutions to world hunger that in the end had made little to no impact. His paper played a significant role in finally changing the focus of international development policy from the mid-1970s onwards.