Decoupled but reconcilable: a nutrition-feasible global reallocation lowers dietary inflammation and environmental footprints simultaneously in every country

Background

Pro-inflammatory and high-environmental-impact diets both threaten population and planetary health, but whether the two objectives align or conflict across countries is unresolved. We tested whether a supply-based dietary inflammatory index (sDII) is coupled to greenhouse-gas (GHG), land and water footprints, and whether a nutrition-feasible reallocation can reduce both at once.

Methods

From FAO Food Balance Sheets we built sDII (12 inflammatory-weighted components; construct validity r=0.9999) and five per-capita footprints using three independent life-cycle inventories for 182 national food-supply series. For each country, constrained optimisation reallocated 13 food-group multipliers while holding energy within ±3% and protein ≥98% of baseline (isoenergetic, isoprotein), under inflammation-first, balanced-Pareto and environment-first weightings. Global totals were population-weighted; avoided emissions were anchored to an external 11.4 Gt CO₂e/yr baseline (95% CI 8.2‒14.7). Avoidable metabolic-syndrome (MetS) cases used a log-linear per-DII-unit RR=1.044 (1.01‒1.07).

Results

sDII was only weakly associated with GHG (Spearman ρ=0.14), land (ρ=0.13) and freshwater (ρ=0.28) in 2023. The balanced-Pareto reallocation lowered both sDII and GHG in 182/182 series (100% synergy) : population-weighted ΔsDII=−0.235, GHG −37.5%, land −49.3%, water −17.2%, i.e. 4.28 Gt CO₂e/yr avoided (3.08‒5.51). Median shifts cut sugar (−100%), ruminant meat (−80%) and pork (−70%) and raised legumes (+200%), nuts/seeds (+123%) and fruit/vegetables (+58%), matching EAT‒Lancet directions. Across 164 countries (7.71 billion people), 23.2 million MetS cases/yr (RR-CI 5.4‒36.4; 1.1% of the 2,092-million pool) were potentially avertable. Synergy stayed 100% under conservative-to-ambitious bounds (GHG −23.6% to −44.8%) and across inventories (rank ρ=0.972‒0.976).

Conclusions

Anti-inflammatory and low-carbon goals are decoupled rather than conflicting, and an isoenergetic, protein-preserving reallocation reconciles them in every country. Environmental gains are large and robust; health gains are directionally consistent but modest― triangulation, not a causal claim.

Key messages

• At the country level, dietary inflammatory potential and environmental footprints are decoupled (|Spearman ρ|≤0.30), so neither goal automatically delivers the other.

• A nutrition-feasible (isoenergetic, protein-preserving) reallocation achieves 100% country-level synergy , cutting population-weighted dietary GHG by 37.5% (4.28 Gt CO₂e/yr) and land use by 49.3%.

• The result is robust to three life-cycle inventories and three feasibility-bound regimes; the associated reduction in metabolic-syndrome burden is directionally consistent but small (∼1.1% of the prevalent pool).