Background Meat and dairy substitutes are gaining popularity, but their expected overall impact on health remains unclear. Objectives We aimed to simulate the complete substitution of meat, milk, and dairy desserts with plant-based substitutes (PBSs) to assess the impact on nutrient deficiency risk and chronic disease–related mortality. Methods Using individual baseline dietary data from adults in the latest French national survey (N = 2121; INCA3), we simulated isoenergetic diets where all meat, milk, and dairy desserts were replaced by an equivalent amount of PBSs. We constructed average PBS profiles of varying nutritional quality (high, average, and low) based on the nutrient compositions of 96 PBSs and legumes. Intermediate scenarios (meat-only or dairy-only substitution) were also analyzed. Deficiency risk was assessed using the nutrient security of the diet (SecDiet) probabilistic system, and the number of deaths averted was projected using the Preventable Risk Integrated ModEl. Results On average, PBS did not increase overall risk of deficiency (SecDiet score: 0.90 ± 0.11 to 0.91 ± 0.11, compared with 0.91 ± 0.11 in the observed diet). However, replacing meat and dairy products increased risk of riboflavin and vitamin B-12 deficiency. Using meat PBS—with reduced consumption of red and processed meat, increased fiber, and improved fatty acid intake—would be the most effective in reducing premature deaths from cardiometabolic diseases and cancer. However, meat PBS led to higher sodium intake, which would slightly offset these benefits. Overall, replacing meat and dairy with PBS would avert between 3721 (95% uncertainty interval: 2712, 4713) and 6671 (95% uncertainty interval: 5527, 7778) deaths from chronic diseases annually, depending on the quality of the PBS (nutrient content and energy density). Conclusions As modeled, full substitution of animal products with PBS can result in limited increases in deficiency risk, and decreases in chronic disease–related mortality, with meat replacement providing most of the benefits. Expected effects vary widely depending on the nutritional quality of the substitutes.
