Towards the in Silico Design of Diets: A Method for Reference Diet Templates Based on Objective Data and Institution Guidelines

Background: In silico diet design may represent a flexible approach in diet planning and adaptation to a variety of conditions, and it may take advantage from standard diet(s) as reference template(s). The concept of standard diet(s) is, however, quite vague and poorly defined. Objective: The aim of this work was to develop templates of omnivorous (OMN), lacto-ovo-vegetarian (LOV), and vegan (VEG) standard diets, based on data produced in European countries and the USA in 1998–2024, and adapted to an adult subject requiring ≈2200 kcal/day. Design: Online databases were used to identify papers containing experimentally determined (EXP) data of daily food frequencies, or reporting dietary recommendations (REC) from (inter)national agencies or specific studies. Only sources reporting quantitative food data (as g/day) in OMN, LOV, and VEG diets were accepted. Results: Out of >200 publications initially identified, 24 EXP and 20 REC sources complied with the selection criteria. By combining the EXP and REC data within each diet type, total meat intake in OMN diet was 99 ± 36 g/day. Total dairy food in LOV diets (247 ± 107 g/day) tended to be lower (by ≈15%, NS) than in OMN diets (272 ± 100). In VEG diets, total vegetal foods were ≈33% greater than in LOV (p < 0.01), and ≈1-fold greater than in OMN ones (p < 0.00001). Total cereal foods were similar in OMN (272 ± 122) and LOV (264 ± 122) diets, but tended to be ≈20–25% greater in VEG diets (to 326 ± 103, NS). Potato and other starchy foods were not different among the three diets. Legumes and pulses were modestly but insignificantly greater in LOV (55 ± 25) and VEG diets (112 ± 137) than in OMN ones (31 ± 24). Soy products were greater in VEG than in LOV diets. The “nuts, seeds, and spreads” food group in VEG diets was ≈3-fold greater than in OMN (p < 0.0005), and ≈90% greater than in LOV diets (p < 0.002). Fruit intake in VEG diets was ≈14% (p = NS) and ≈ 60% (p < 0.005) greater than in LOV and OMN diets, respectively. Finally, the “protein and energy-rich vegetal alternatives” food group in LOV and VEG diets was ≈5- to ≈6-fold greater than in the OMN diet (p ≤ 0.001). Conclusions: The exclusion of meat, fish, and egg in LOV diets is not compensated by increased dairy foods, rather by more total vegetal foods and protein-rich vegetal alternatives. VEG diets replace animal-derived proteins mainly with nuts, seeds, and spreads, soy products and protein-rich vegetal alternatives. On the basis of these data, templates to design “standard” OMN, LOV, and VEG diets are proposed.