Abstract
Abstract The production of animal-based foods is associated with higher greenhouse gas (GHG) emissions than plant-based foods. The objective of this study was to estimate the difference in dietary GHG emissions between self-selected meat-eaters, fish-eaters, vegetarians and vegans in the UK. Subjects were participants in the EPIC-Oxford cohort study. The diets of 2,041 vegans, 15,751 vegetarians, 8,123 fish-eaters and 29,589 meat-eaters aged 20–79 were assessed using a validated food frequency questionnaire. Comparable GHG emissions parameters were developed for the underlying food codes using a dataset of GHG emissions for 94 food commodities in the UK, with a weighting for the global warming potential of each component gas. The average GHG emissions associated with a standard 2,000 kcal diet were estimated for all subjects. ANOVA was used to estimate average dietary GHG emissions by diet group adjusted for sex and age. The age-and-sex-adjusted mean (95 % confidence interval) GHG emissions in kilograms of carbon dioxide equivalents per day (kgCO2e/day) were 7.19 (7.16, 7.22) for high meat-eaters (>=100 g/d), 5.63 (5.61, 5.65) for medium meat-eaters (50-99 g/d), 4.67 (4.65, 4.70) for low meat-eaters (<50 g/d), 3.91 (3.88, 3.94) for fish-eaters, 3.81 (3.79, 3.83) for vegetarians and 2.89 (2.83, 2.94) for vegans. In conclusion, dietary GHG emissions in self-selected meat-eaters are approximately twice as high as those in vegans. It is likely that reductions in meat consumption would lead to reductions in dietary GHG emissions.
Generated Summary
This study, published in Climatic Change, investigates the dietary greenhouse gas (GHG) emissions associated with different dietary patterns in the UK. The research utilized data from the EPIC-Oxford cohort study, assessing the diets of 2,041 vegans, 15,751 vegetarians, 8,123 fish-eaters, and 29,589 meat-eaters. The study aimed to estimate the differences in dietary GHG emissions between these self-selected diet groups. The methodology involved developing comparable GHG emission parameters for food codes, using a dataset of GHG emissions for 94 food commodities in the UK and weighting for the global warming potential of each gas component. Average GHG emissions were estimated for all subjects, and ANOVA was used to estimate average dietary GHG emissions by diet group, adjusted for sex and age. The study’s approach allows for a direct comparison of GHG emissions across different dietary habits, offering insights into the environmental impact of various food choices and the potential benefits of dietary changes.
Key Findings & Statistics
- The study found that the age-and-sex-adjusted mean GHG emissions in kilograms of carbon dioxide equivalents per day (kgCO2e/day) were: 7.19 (7.16, 7.22) for high meat-eaters (>=100 g/d), 5.63 (5.61, 5.65) for medium meat-eaters (50-99 g/d), 4.67 (4.65, 4.70) for low meat-eaters (<50 g/d), 3.91 (3.88, 3.94) for fish-eaters, 3.81 (3.79, 3.83) for vegetarians and 2.89 (2.83, 2.94) for vegans.
- The highest dietary GHG emissions were found in high meat-eating men, and the lowest in vegan women.
- The mean observed values of dietary GHG emissions for meat-eaters were 46% and 51% higher than for fish-eaters, 50% and 54% higher than for vegetarians, and 99% and 102% higher than for vegans.
- The study found that the average 2,000 kcal high meat diet had 2.5 times as many GHG emissions as a 2,000 kcal vegan diet.
- Reducing the amount of animal-based products in the diet could reduce an individual’s carbon footprint. Moving from a high meat diet to a low meat diet would reduce carbon footprint by 920kgCO2e every year, moving from a high meat diet to a vegetarian diet would reduce the carbon footprint by 1,230kgCO2e/year, and moving from a high meat diet to a vegan diet would reduce the carbon footprint by 1,560kgCO2e/year.
- A recent survey found that the average amount of meat consumed in adults aged 19–64 (including non-consumers) was 110 g/day, which suggests that the majority of adults in the UK would be categorized as ‘high meat consumers’.
Other Important Findings
- The study observed significant trends towards lower saturated fat, higher fiber, and higher fruit and vegetable intake as the quantity of animal-based products in the diet decreased.
- The results of the ANOVA analysis showed highly statistically significant differences (p<0.0001) in dietary GHG emissions between the six diet groups after adjustment for age and sex.
- The study also found that meat-eaters tended to be older than fish-eaters, vegetarians, and vegans.
- The authors noted that reducing meat consumption has the potential to be a ‘healthy, sustainable diet’.
- The study acknowledges that the current trend in the UK is towards increased meat consumption, with a decrease in the percentage of vegetarians and vegans.
Limitations Noted in the Document
- The GHG emissions estimates for food items are subject to uncertainty that is not captured in the confidence intervals.
- Estimates of total food-related GHG emissions using measurements of food consumption are underestimates because they do not take account of food wastage.
- Consumption estimates derived from FFQs are also prone to under-reporting.
- The diets observed in the EPIC-Oxford cohort may not represent current consumption patterns in the UK due to the data collection period being in the 1990s.
- A large proportion of the meat-eaters in the EPIC-Oxford cohort consists of family or friends of vegetarians and vegans, who are likely to have diets which differ from those of the general population in the UK.
- The study’s data are based on cross-sectional comparisons between dietary groups, and as such they do not tell us how people would replace meat in the diet, which is an important limitation.
Conclusion
The study’s key finding is the clear positive relationship between dietary GHG emissions and the consumption of animal-based products. The results show that high meat diets have significantly higher GHG emissions compared to diets with reduced or no meat consumption. The study’s authors emphasize that reducing the intake of meat and other animal-based products can be a valuable contribution to climate change mitigation. This aligns with the broader discussion on the need for a ‘healthy, sustainable diet,’ which the authors suggest should include recommendations to lower the consumption of animal-based products. The study’s implications are significant, suggesting that dietary choices have a tangible impact on environmental sustainability and that national governments should consider these findings when updating dietary recommendations. The authors draw upon previous research that shows a correlation between diets with lower intakes of animal products and lower body mass index and fewer ischemic heart disease events, supporting the idea that such dietary changes can contribute to both environmental and public health benefits. The authors also acknowledge the challenges of reducing meat intake, such as the need to monitor nutrient intake, particularly iron and zinc, in those reducing or eliminating animal products from their diet, and the need for further research in this area. The study highlights the importance of considering the environmental impact of food choices as part of a comprehensive approach to addressing climate change and promoting public health.