Digestion, Metabolism, and Health Effects of Plant Proteins and Their Food Formulations: A Systematic Scoping Review of Clinical Postprandial Studies and <i>in vitro</i> Methods

Plant proteins are gaining attention as sustainable alternatives to animal proteins, but their bioaccessibility, bioavailability, and health effects remain underexplored. This review summarizes current knowledge on the digestion, metabolism, and health impacts of plant proteins, emphasizing clinical postprandial studies and in vitro methods. A systematic scoping review was conducted following PRISMA-ScR guidelines, identifying 98 relevant articles published between 2000 and 2023. Clinical studies showed that amino acid absorption and the increase in blood amino acid concentrations were slower after plant protein-based meals compared with animal-based meals. Plant proteins also tended to reduce glucose responses, especially when combined with fiber, and elicited varied gastrointestinal hormone responses. In vitro studies highlighted that protein digestibility is significantly influenced by the food matrix and processing methods. Both clinical and in vitro approaches offer complementary insights into plant protein metabolism. Strategies such as fermentation and heat treatment can enhance digestibility, supporting their role as viable, sustainable protein sources for adults. However, the role of gut microbiota in digestion and health outcomes remains largely overlooked. Additionally, more research is needed to understand the digestion of plant proteins in vulnerable populations, such as older adults.