Partially Replacing Animal-Based Protein Foods With Plant-Based Protein Foods: A Systematic Review of Randomized...

Increasing our intake of plant-based protein may help improve both population and planetary health. A systematic synthesis of randomized controlled trials is needed to clarify evidence on the effects of increased plant-based protein intake.

To evaluate the effects of partially replacing animal-based protein with plant-based protein in healthy adult cohorts for any outcome.

On December 5, 2024, 3 databases were searched (PubMed, Cochrane, Embase). Articles were included for evaluation if the partial replacement of animal-based protein with plant-based sources was assessed for any outcome in a healthy adult cohort (mean or median age between 18 and 65 years) in a randomized controlled trial.

Articles were screened at title, abstract, and full-text levels independently by 2 researchers. Results were extracted and synthesized.

Risk of bias was assessed using the Cochrane Risk-of-Bias tool, version 2.0. Four dietary interventions reported in 7 articles were included in the final analysis. Three articles obtained a low risk-of-bias result, and the remaining 4 were identified to have "some concerns." Vitamin B12 status was reduced significantly in those consuming diets with the highest proportion of plant-based protein, whereas the status of other micronutrients (specifically, folate, iron, and vitamin D) was not affected. Mixed evidence was reported on the impact on bone and mineral metabolism. Improvements in cardiovascular risk biomarkers (low-density lipoprotein cholesterol, total cholesterol, and body weight) were observed in those consuming higher proportions of plant-based protein. One study reported that the diet with reduced meat also was associated with reduced estimated greenhouse gas emissions.

Replacing animal protein with some plant-based sources may improve certain biomarkers of cardiovascular disease risk and reduce the environmental impact of dietary intake. Mixed findings for nutrient status and bone and mineral metabolism highlight the need for further research to support integration of sustainable diets into food-based dietary guidelines.

PROSPERO registration No. CRD42024584913.