The role of ultra-processed foods in plant-based diets: associations with human health and environmental sustainability.

Purpose: Investigate the associations of ultra-processed foods (UPF) in healthful (hPDI) and unhealthful (uPDI) plant-based diets with all-cause mortality, greenhouse gas emissions (GHGE), and blue water consumption (BWC).

Methods: Analyses were based on 35,030 participants (20-70 years; 74% females) from the EPIC-NL cohort who were followed up from 1993 to 1997 through 2014. Plant-based diet indices (hPDI and uPDI) and UPF consumption were calculated from a validated FFQ, assessed at baseline. Cox proportional hazard and multiple linear regression models were used to estimate associations between combined quartiles of the PDI indices and UPF consumption.

Results: With lower hPDI and higher UPF diets as the reference, we observed the following. Risk estimates of all-cause mortality were 0.98 (95% CI: 0.83, 1.16) for lower UPF consumption, 0.86 (95% CI: 0.68, 1.08) for higher hPDI, and 0.78 (95% CI: 0.66, 0.89) for combined higher hPDI and lower UPF consumption. Results with the uPDI were inconclusive. Mean differences in GHGE and BWC were 1.4% (95% CI: 0.3, 2.4) and 1.6% (95% CI: -0.5, 3.7) for lower UPF consumption, -7.4% (95% CI: -8.6, -6.4) and 9.6% (95% CI: 7.2, 12.0) for higher hPDI, and - 6.8% (95% CI: -7.4, -6.1) and 13.1% (95% CI: 11.6, 14.8) for combined higher hPDI and lower UPF consumption. No apparent conflict between environmental impacts was observed for the uPDI; GHGE and BWC were lower for higher uPDI scores.

Conclusion: Mortality risk and environmental impacts were mostly associated with the amount of plant-based foods and to a lesser extent UPF in the diet. Shifting to a more healthful plant-based diet could improve human health and reduce most aspects of environmental impact (GHGE, but not BWC) irrespective of UPF consumption.