This review discusses the role of different protein sources in human nutrition, focusing on their structure, digestibility, and bioavailability. Plant-based proteins, such as those from legumes, nuts, and seeds, may contain anti-nutritional factors that affect their bioavailability. Animal proteins are generally more digestible and have higher amino acid bioavailability. The processing methods of alternative protein sources can alter their structure and nutritional value. The review also covers the nutritional requirements for various population groups, including adults, older adults, children, and special groups like pregnant women and athletes. It highlights the importance of protein quality measures, such as the Digestible Indispensable Amino Acid Score (DIAAS) and Protein Digestibility-Corrected Amino Acid Score (PDCAAS), in assessing protein quality. The impact of protein structure on digestibility and bioavailability is discussed, along with the effects of processing on protein structure. The review explores future food proteins, including cultured meat, plant-based proteins, single-cell protein, and insect protein, and their potential to meet nutritional needs while reducing environmental impacts. Finally, it addresses the risk of food allergies associated with future proteins and the need for intensive clinical examination before market launch.This review discusses the role of different protein sources in human nutrition, focusing on their structure, digestibility, and bioavailability. Plant-based proteins, such as those from legumes, nuts, and seeds, may contain anti-nutritional factors that affect their bioavailability. Animal proteins are generally more digestible and have higher amino acid bioavailability. The processing methods of alternative protein sources can alter their structure and nutritional value. The review also covers the nutritional requirements for various population groups, including adults, older adults, children, and special groups like pregnant women and athletes. It highlights the importance of protein quality measures, such as the Digestible Indispensable Amino Acid Score (DIAAS) and Protein Digestibility-Corrected Amino Acid Score (PDCAAS), in assessing protein quality. The impact of protein structure on digestibility and bioavailability is discussed, along with the effects of processing on protein structure. The review explores future food proteins, including cultured meat, plant-based proteins, single-cell protein, and insect protein, and their potential to meet nutritional needs while reducing environmental impacts. Finally, it addresses the risk of food allergies associated with future proteins and the need for intensive clinical examination before market launch.