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Abstract
Objective To compare the costs and climate impact (greenhouse gas emissions) associated with current and healthy diets and two healthy and environmentally friendly dietary patterns: flexitarian and vegan.
Design Modelling study
Setting Aotearoa (New Zealand).
Main outcome measures The distribution of the cost and climate impact (kgCO2e/kg of food per fortnight) of 2 weekly current, healthy, vegan and flexitarian household diets was modelled using a list of commonly consumed foods, a set of quantity/serves constraints for each, and constraints for food group and nutrient intakes based on dietary guidelines (Eating and Activity Guidelines for healthy diets and EAT-Lancet reference diet for vegan and flexitarian diets) or nutrition survey data (current diets).
Results The iterative creation of 210–237 household dietary intakes for each dietary scenario was achieved using computer software adapted for the purpose (DIETCOST). There were stepwise differences between diet scenarios (p<0.001) with the current diet having the lowest mean cost in New Zealand Dollars (NZ$584 (95% CI NZ$580 to NZ$588)) per fortnight for a family of four) but highest mean climate impact (597 kgCO2e (95% CI 590 to 604 kgCO2e)), followed by the healthy diet (NZ$637 (95% CI NZ$632 to NZ$642), 452 kgCO2e (95% CI 446 to 458 kgCO2e)), the flexitarian diet (NZ$728 (95% CI NZ$723 to NZ$734), 263 kgCO2e (95% CI 261 to 265 kgCO2e)) and the vegan diet, which had the highest mean cost and lowest mean climate impact (NZ$789, (95% CI NZ$784 to NZ$794), 203 kgCO2e (95% CI 201 to 204 kgCO2e)). There was a negative relationship between cost and climate impact across diets and a positive relationship within diets.
Conclusions Moving from current diets towards sustainable healthy diets (SHDs) will reduce climate impact but generally at a higher cost to households. The results reflect trade-offs, with the larger constraints placed on diets, the greater cost and factors such as nutritional adequacy, variety, cost and low-emissions foods being considered. Further monitoring and policies are needed to support population transitions that are country specific from current diets to SHD.
- dietary patterns
Data availability statement
The data from this research will not be publicly available as it is specific to the DIETCOST programme and would have little relevance to the public. Third parties will be allowed to ask for permission to access the data if deemed appropriate to do so by the study authors.
This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
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Data availability statement
The data from this research will not be publicly available as it is specific to the DIETCOST programme and would have little relevance to the public. Third parties will be allowed to ask for permission to access the data if deemed appropriate to do so by the study authors.
Supplementary materials
Supplementary Data
This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.
Supplementary Data
This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.
Supplementary Data
This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.
Footnotes
Twitter @bk3611
Contributors BK contributed to the study conception and design, and led the data collection, analysis and writing of the manuscript. SM contributed to the study conception and design, data analysis and assisted with writing and critically revised the manuscript. SV contributed to the study conception and design, and critically revised the manuscript. BS contributed to the study conception and design and critically revised the manuscript.
Funding The funding source of the contributing authors included the main author receiving the University of Auckland Research Masters Scholarship as part of completing the research in the Master of Public Health programme at the University of Auckland. No other funding sources were involved.
Disclaimer This study is based on population level data that cannot be attributed to individuals and is publicly available. No patients or members of the public were involved in the study.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed by Malcolm Riley, CSIRO Australia.
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