The human diet comprises both plant and animal protein, with considerable regional variation and greater reliance on animal protein in richer Western nations. Animal protein is less efficient in its use of land, water and energy resources than plant protein, and is associated with significant atmospheric emissions contributing to climate change. It also has adverse health consequences for many consumers. Food security worldwide is threatened by a growing reliance on animal protein, with developing countries increasing consumption of animal products in response to growing prosperity and a desire to emulate Western diets. Although a range of drivers contributes to some consumers shifting to more plant-rich diets, this trend is insufficient to stem the rapid rise in meat consumption. Meat products are being developed using cell-based technologies, but these are yet to become commercially available. They also challenge the animal-plant protein dichotomy. This dynamic situation needs to be managed nationally and internationally to avert the dire consequences of an over-reliance on animal protein.