Effect of food swap recommendations on the healthfulness and carbon footprint of grocery purchases in a naturalistic online store: A randomized parallel trial
by Anna H. Grummon, Kevin O’Sullivan, Amanda B. Zeitlin, Lindsey Smith Taillie, Cristina J. Y. Lee, Ashe J. Walker, Verena Tiefenbeck, Elgar Fleisch, Clayton Ulm, Thomas N. Robinson Background Modeling studies suggest that simple dietary “swaps” in which just one food is replaced with another could yield both health and environmental benefits, but it remains unclear whether consumers make such…
A randomized parallel trial published in May–June 2025 investigated the impact of food swap recommendations on the healthfulness and carbon footprint of grocery purchases in a simulated online grocery store. One thousand two hundred one US adults, aged 18 and above, participated in the study and were randomly assigned to one of four arms: climate swaps, health swaps, climate + health swaps, or a control group.
Participants completed three weekly shopping visits. In the first visit, they shopped in an online grocery store without any intervention, serving as the no-intervention baseline. In the subsequent visits, they completed the shopping task in their assigned trial arm.
The primary endpoints assessed were the healthfulness and carbon footprint of participants' grocery selections. The healthfulness was measured using the average Ofcom Nutrient Profiling Model score (ranging from 1 to 100), while the carbon footprint was measured as the average kg of carbon dioxide equivalents (CO2-eq) per kg associated with producing the selected items.
Compared to the control group, all three swap arms (climate, health, and climate + health) improved the healthfulness of participants' selections, as indicated by higher Ofcom Nutrient Profiling Model scores (p ≤ 0.02). However, there was no significant difference between the health swap, climate swap, and climate + health swap arms (p = 0.34).
In terms of carbon footprint, only the climate swap demonstrated a significant reduction compared to the control group (p < 0.001). The climate and climate + health swaps led to larger reductions in carbon footprint than the health swap alone (p < 0.05). Importantly, the effects of swaps on healthfulness and carbon footprint did not differ based on age, health consciousness, or environmental consciousness (p ≥ 0.10 for interactions).
The study had limitations, including a sample that differed somewhat from the general US population and the findings may not generalize to brick-and-mortar stores. The trial was registered on ClinicalTrials.gov (NCT#06648226) and submitted for approval on October 16, 2024.
Written by urgent.news from PLOS Medicine's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
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