Beyond conventional dietary animal and plant proteins: a “systematized review of reviews” with a pilot consumer perception survey about alternative protein sources

Dietary proteins are essential macronutrients involved in structural, metabolic, immune, and endocrine functions, whose quality is determined by amino acid composition, digestibility, and overall indispensable nutritional value. Due to the increasing environmental constraints on conventional proteins with agronomic origins, alternative protein sources have gained growing interest as potential dietary contributors to sustainable food systems. This current systematized mapping review of reviews screened emerging non-animal protein sources, including edible mushrooms, mycoproteins, microbial proteins, cultured meat, and 3D-structured food matrices. The analysis focuses on protein content, digestibility, essential amino acid profiles, and functional properties, alongside sustainability-related considerations. The review is complemented by a pilot consumer perception survey conducted in two Mediterranean countries (Italy and Spain) sharing similar dietary patterns, to explore acceptance and attitudes toward these novel protein sources. Overall, this study reports consistent evidence on the nutritional and functional characteristics of alternative proteins, highlighting their potential benefits, key limitations, and challenges for integration into future dietary frameworks and sustainable food systems, as well as relevant consumer information about alternative proteins via an online survey concerning knowledge, acceptability, perceived importance of key attributes and willingness to consume, and purchasing preferences.