Regulatory heterogeneity, trade mediation and nutrient intake: The case of Trans fat

• Trans fat policies reduce its intake, but effectiveness varies by policy stringency. • When domestic standards diverge, cross-border externalities emerge. • Mediation analysis shows trade exposure significantly mediates cross-border policy effects. • Stringent policies curb both intake and imports; weaker ones fail to do so. • With enforcement, less-strict policies can perform nearly as effective as most strict ones. National nutrition regulations can shape diets in two distinct ways: directly, through domestic policy mechanisms, and indirectly, by mediating trade flows. This study assesses how trans fat (TF) intake is affected by both pathways. When countries act alone – by banning or limiting TF – their rules often differ in timing, stringency, and enforcement. The resulting regulatory heterogeneity can create loopholes that allow unhealthy products to move across borders. This study estimates the causal effects of TF regulations on its intake nationally by constructing a food-item-level panel dataset for 161 countries (2010–2022, validated with established benchmarks), and applying a staggered difference-in-differences approach combined with mediation analysis. The findings show that strict, enforceable regulations, such as those in the United States and European Union, significantly reduce TF intake and imports, acting as effective filters against TF-rich foods. In contrast, countries with weaker regulations experience rising TF imports and, eventually, increased intake, effectively placing them at risk of becoming “dietary risk havens.” Even modest rules work better when backed by strong monitoring. These results are robust to alternative specifications such as controlling for importer-specific foreign regulatory exposure. The causal evidence demonstrates that unilateral action delivers meaningful health gains, but fragmented regulatory approaches create opportunities for “regulatory dumping.” This study underscores the need for global cooperation – through harmonized standards or trade-linked enforcement – to prevent cross-border displacement of dietary risks. Beyond TF, the findings offer timely insights for emerging national and global mandates on other nutrients, such as salt, sugar, and saturated fats.