BackgroundClimate change is real and so are its unequal impacts on different geographies and societies. Food systems are estimated to produce a third of global greenhouse gas emissions, of which meat is a major contributor. An emerging challenge is feeding a growing population and fulfilling its protein needs, while limiting the climate footprint. Though more environment friendly alternative sources of proteins are becoming available, their acceptance will depend upon attitudes, beliefs, and behavioural choices. For Muslims, who comprise about a quarter of the world's population, religious guidance plays an important role in consumption patterns and food choices.Scope and approachThis review looks at consumption practices among Muslims in the context of food system impacts on greenhouse gas emissions, and the need for optimal sources of protein for nutrition and achieving food security. It discusses what is permissible (halāl) or prohibited (harām) for Muslims and how that is determined based on two primary sources – the Qur'an and the Hadith – and other secondary sources relied upon by Muslim legists. It then reviews what is known about three alternative protein sources – plant-based diets, insects and cultured meat, and the Islamic ethical and legal position related to these foods.Key findings and conclusionsThe findings show conflicting scholarly opinions and a limited understanding of Muslim attitudes to alternative protein sources. Better understanding will be required for enhancing food security, while limiting food related greenhouse gas emissions.