Health and Environmental Implications of Alternative Proteins in Human Diets: Nutritional Value, Gut Microbiota Modulation, and Sustainability Perspectives

Abstract The increasing global demand for sustainable and nutritious food has intensified interest in alternative proteins as potential contributors to healthier diets and lower-impact food systems. This review critically examines the health and environmental implications of major alternative protein sources, including plant-based, insect, microalgal, fungal/mycoprotein, precision-fermented, and cell-cultured proteins. It discusses their classification, production pathways, nutritional quality, amino acid composition, digestibility, micronutrient content, and functional properties in food systems. The review also summarizes current evidence regarding their effects on diet quality, metabolic health, systemic inflammation, and gut microbiota modulation. While plant-based proteins and mycoprotein show comparatively stronger evidence for beneficial health outcomes, newer protein systems still require further long-term clinical validation. From an environmental perspective, alternative proteins generally demonstrate advantages over conventional animal proteins in terms of greenhouse gas emissions, land use, and water demand, although trade-offs related to energy use, processing intensity, and scalability remain important. In addition, this review highlights major barriers to adoption, including sensory limitations, technological challenges, economic constraints, consumer acceptance, and regulatory issues. Overall, alternative proteins represent a promising pathway toward sustainable food system transformation, but their successful integration will depend on evidence-based development, improved processing strategies, standardized evaluation, and supportive policy frameworks.