PURPOSE: A transition to more plant-rich diets is an effective way to reduce the climate impact of a diet. Using a whole-diet approach, we studied how partial replacement of animal-sourced with plant-sourced proteins affected the dietary climate impact while simultaneously considering diet-related health biomarkers. METHODS: In a 12-week randomised controlled trial, 107 women and 29 men were assigned into three diet groups (ANIMAL, 50/50, PLANT) with animal-to-plant-protein ratios of 70/30, 50/50, and 30/70, respectively. Life-cycle-assessment-based coefficients for foods were used to assess the climate impact of the diet groups, based on four-day food records. Correlations between climate impact and biomarkers were assessed. RESULTS: The climate impact (CO CONCLUSION: Replacing animal-sourced proteins with plant-sourced proteins reduced the climate impact of the diet. The relationship between climate impact and biomarkers was more ambiguous indicated by both beneficial and harmful indicators within lower climate impacts. CLINICAL TRIAL REGISTRY: NCT03206827
registration date: 2017-06-30.