Carbon tunnel vision and sustainable meat production in the West: A disproportionate focus on dietary greenhouse gas emissions?

BackgroundHealth authorities are increasingly integrating environmental sustainability considerations into food-based dietary guidelines. However, concerns persist about the accuracy of the data used to assess environmental impacts, as well as the extent to which these guidelines are followed in practice. AimTo compare dietary greenhouse gas (GHG) emissions estimates using different top-down and bottom-up life cycle assessment (LCA) databases; and to estimate GHG emissions of food consumption within the ranges set for meat and dairy in recently proposed environmentally sustainable diets. MethodsDietary GHG emissions were estimated for participants in the 2019–2021 Icelandic National Dietary Survey (n = 822) using three publicly available LCA databases from Denmark, the US, and France. GHG emissions among participants whose consumption was aligned with the EAT-Lancet diet, the 2021 Danish food-based dietary guidelines and the 2023 Nordic Nutrition Recommendations were also quantified. ResultsThe mean dietary GHG emissions among participants were 6.3, 6.1, and 6.1 kg CO2-eq/day based on the Danish (top-down), US (bottom-up), and French (bottom-up) databases, respectively. The relative ranking of foods was also consistent across all three databases. For example, the relative contribution of total CO2-eq (% range for the three databases) was highest for red meat (39–51%), followed by dairy (10–17%) and beverages (9–13%). The contribution from plant-based foods (6–10%), seafood (4–11%), and poultry/eggs (<5%) was modest. The dietary habits of most participants (86%) were outside the ranges for meat and dairy consumption as set by the three sustainable diets. However, participants reporting consumption within the ranges for meat and dairy had mean GHG emissions ranging between 4.2 and 4.7 kg CO2-eq/day, depending on the diet. In comparison, the mean for participants not adhering to the sustainable diets was 7.7 kg CO2-eq/day. These results are higher than those reported in other Nordic and European studies, likely due to high consumption of lamb, beef, and dairy, and low consumption of plant-based food. ConclusionAll three LCA databases provided similar estimates for total dietary GHG emissions and relative ranking of different food groups. Based on current dietary habits in Iceland, adherence to environmentally sustainable diets would lead to a substantial reduction in dietary GHG emissions.

BackgroundThe Planetary Health Diet Index (PHDI) measures adherence to the dietary pattern presented by the EAT-Lancet Commission, which aligns health and sustainability targets. There is a need to understand how PHDI scores correlate with dietary greenhouse gas emissions (GHGE) and how this differs from the carbon footprints of scores on established dietary recommendations. The objectives of this study were to compare how the PHDI, Healthy Eating Index-2015 (HEI-2015) and Dietary Approaches to Stop Hypertension (DASH) relate to (a) dietary GHGE and (b) to examine the influence of PHDI food components on dietary GHGE.MethodsWe used life cycle assessment data from the Database of Food Recall Impacts on the Environment for Nutrition and Dietary Studies to calculate the mean dietary GHGE of 8,128 adult participants in the 2015–2016 and 2017–2018 cycles of the National Health and Nutrition Examination Survey (NHANES). Poisson regression was used to estimate the association of (a) quintiles of diet score and (b) standardized dietary index Z-scores with dietary GHGE for PHDI, HEI-2015, and DASH scores. In secondary analyses, we used Poisson regression to assess the influence of individual PHDI component scores on dietary GHGE.ResultsWe found that higher dietary quality on all three indices was correlated with lower dietary GHGE. The magnitude of the dietary quality-dietary GHGE relationship was larger for PHDI [-0.4, 95% CI (-0.5, -0.3) kg CO2 equivalents per one standard deviation change] and for DASH [-0.5, (-0.4, -0.6) kg CO2-equivalents] than for HEI-2015 [-0.2, (-0.2, -0.3) kg CO2-equivalents]. When examining PHDI component scores, we found that diet-related GHGE were driven largely by red and processed meat intake.ConclusionsImproved dietary quality has the potential to lower the emissions impacts of US diets. Future efforts to promote healthy, sustainable diets could apply the recommendations of the established DASH guidelines as well as the new guidance provided by the PHDI to increase their environmental benefits.

Plant-rich diets have gained recognition for their environmental sustainability. However, relatively few studies have compared dietary habits of vegans and omnivores in terms of compliance with nutritional recommendations and dietary greenhouse gas (GHG) emissions, which this study aimed to assess. We used data on 651 omnivores and 68 vegans from the Icelandic National Dietary Survey (2019–2021) and a comparable survey on vegans (2022–2023), respectively. The median dietary GHG emissions was substantially lower among vegans than omnivores (2.6 vs. 5.3 kg CO2-eq/day). Compared to omnivores, vegans had a proportionally higher intake of energy from carbohydrates (48% vs. 39%) but a lower intake from fat (35% vs. 40%) and proteins (12% vs. 18%). More vegans compared to omnivores fell within the dietary recommendations for fiber (74% vs. 8%) and saturated fat (56% vs. 7%) while vegans were less likely to have protein intake in line with the recommended ≥ 0.83 g/kg body weight (52% vs. 79%). Despite frequent use of dietary food supplements among vegans (97%) and omnivores (72%) the prevalence of those reaching the recommended intake of iodine, calcium and vitamin D, was low (40–60%) in both groups. In conclusion, vegans were overall more compliant with macronutrient recommendations and had substantially lower dietary GHG emissions compared to omnivores. In terms of meeting dietary recommendations, room for improvements was observed in both groups.

Objectives: New food based dietary guidelines (FBDGs) in Iceland 2024, based on the “Nordic Nutrition Recommendations 2023 – integrating environmental aspects” will emphasize diet in childhood. Therefore, our objective was to estimate dietary greenhouse gas (GHG) emissions in Icelandic children’s and adolescents’ diet and to define top food groups that contribute to the GHG emissions in their diet. Methods: Participants were randomly selected in 2003-2012 nation-wide sampling from the Icelandic population registry for 3, 5 and 6 years of age children (n= 618) and from a cluster sampling of schools in all four regions in the country (9 and 15 years of age) (n=366). The participating children at the age of 3, 5 and 6 years completed the 3 day food registration study. The dietary intake of the participating 9 years old children and 15 years old adolescents was collected by two repeated 24-h recalls. Participating children at the age of 3 years were n=225, 5 years n=231, 6 years n=162, 9 years n=183 and 15 years n=183. Dietary intake data were used to estimate dietary GHG emissions, using the life cycle assessment (LCA) database from Denmark. Results: Estimated from dietary GHG emissions increased with age. The mean daily GHG emissions among 3, 5-, 6-, 9- and 15-years old Icelandic children were 2.97, 3.10, 3.45, 4.40 and 5.05 kg carbon dioxide equivalents (CO2eq)/day, respectively. The largest contributors to daily GHG emissions were meat, dairy and fish. For 3 years and 5 years old children meat, dairy and fish contribution of GHG emissions were 28%, 18% and 14% and 26%, 15% and 15 %, respectively. The diet of the 6, 9 and 15 years old children similarly showed that meat contributed by 28% - 30% of the carbon footprint, while dairy contributed by 15% - 25%, being proportionately highest for the youngest group. These values were similar to those of adults in the most recent national dietary survey of adults in Iceland. The GHG of the diet of the younger children give slightly lower GHG emissions, mainly because of a lower intake of meat. Conclusions: The estimated GHG emissions through the Icelandic children’s diet are substantial. New FBDGs will incorporate this consideration in developing dietary guidance to support a sustainable healthier environment from the early stages of life. Funding Sources: Research Fund of the University of Iceland, The Icelandic Research Fund.

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.

Introduction : Food consumption accounts for 20-30% of greenhouse gas emissions in the EU. Certain foods have higher emissions than others and are often the target of policy makers to reduce greenhouse gasses associated with food consumption. However, food policy should aim to address both climatic and health imbalances concurrently and hence have more significant impact. Targeting excessive food consumption as a mitigation strategy for greenhouse gas emissions may also have a concurrent impact on the global obesity epidemic Objective: To evaluate the greenhouse gas emissions (GHGE) associated with the excessive food and energy intake in Irish adults. Methods: A secondary analysis of nationally representative data from the National Adult Food & Nutrition Survey, 2011, was conducted. The demographic characteristics, food consumption patterns and diet-associated GHGEs were compared across categories of increasing levels of relative energy intake. One-way ANOVA (p<0.05) was used to determine the level of significance across quintiles of relative energy intake. Results: Different dietary patterns were evident between the categories of varying relative energy intake. A strong positive correlation (r = 0.736; p< 0.001) was evident between dietary GHGE and the EI relative to one’s requirements. In Irish diets, animal products contributed to a large proportion of total dietary GHGE but accounted for much less of overall EI. Plant-based foods were the lowest contributors to total GHGE. When constructing strategies to mitigate dietary carbon emissions, it is important to carefully consider all aspects of sustainability. The exclusion of certain food groups from the average diet may provoke health, economical and/or cultural repercussions. An adherence to the Irish dietary guidelines, including a decrease of EI, can viably attenuate dietary environmental impact Conclusions: The results offer further evidence to support the hypothesis that excessive energy consumption and the overconsumption of certain food types are detrimental to overall diet-associated carbon emissions levels, and that adhering to the current Irish dietary guidelines can potentially lower dietary related GHGE.

Dietary greenhouse gas emissions and the risk of coronary heart disease and type 2 diabetes

BackgroundThe typical Western diet is associated with high levels of greenhouse gas (GHG) emissions and with obesity and other diet-related diseases. This study aims to determine the impact of adjustments to the current diet at specific moments of food consumption, to lower GHG emissions and improve diet quality.MethodsFood consumption in the Netherlands was assessed by two non-consecutive 24-h recalls for adults aged 19–69 years (n = 2102). GHG emission of food consumption was evaluated with the use of life cycle assessments. The population was stratified by gender and according to tertiles of dietary GHG emission. Scenarios were developed to lower GHG emissions of people in the highest tertile of dietary GHG emission; 1) reducing red and processed meat consumed during dinner by 50% and 75%, 2) replacing 50% and 100% of alcoholic and soft drinks (including fruit and vegetable juice and mineral water) by tap water, 3) replacing cheese consumed in between meals by plant-based alternatives and 4) two combinations of these scenarios. Effects on GHG emission as well as nutrient content of the diet were assessed.ResultsThe mean habitual daily dietary GHG emission in the highest tertile of dietary GHG emission was 6.7 kg CO2-equivalents for men and 5.1 kg CO2-equivalents for women. The scenarios with reduced meat consumption and/or replacement of all alcoholic and soft drinks were most successful in reducing dietary GHG emissions (ranging from − 15% to − 34%) and also reduced saturated fatty acid intake and/or sugar intake. Both types of scenarios lead to reduced energy and iron intakes. Protein intake remained adequate.ConclusionsReducing the consumption of red and processed meat during dinner and of soft and alcoholic drinks throughout the day leads to significantly lower dietary GHG emissions of people in the Netherlands in the highest tertile of dietary GHG emissions, while also having health benefits. For subgroups of the population not meeting energy or iron requirements as a result of these dietary changes, low GHG emission and nutritious replacement foods might be needed in order to meet energy and iron requirements.

Evidence from the scientific literature shows a significant variation in greenhouse gas (GHG) emissions from the diet, according to the type of food consumed. We aim to analyze the relationship between the daily dietary GHG emissions according to red meat, fruit and vegetables consumption and their relationship with risk of total mortality, and incident risk of chronic diseases. We examined data on the EPIC-Spain prospective study, with a sample of 40621 participants. Dietary GHG emission values were calculated for 57 food items of the EPIC study using mean emission data from a systematic review of 369 published studies. Dietary GHG emissions (kgCO2eq/day), per 2000kcal, were 4.7 times higher in those with high red-meat consumption (>140g/day) than those with low consumption (<70g/day). The average dietary GHG emissions were similar in males and females, but it was significantly higher in youngest people and in those individuals with lower educational level, as well as for northern EPIC centers of Spain. We found a significant association with the risk of mortality comparing the third vs. the first tertile of dietary GHG emissions [hazard ratio (HR) 1.095; 95% confidence interval (CI) 1.007-1.19; trend test 0.037]. Risk of coronary heart disease (HR 1.26; 95% CI 1.08-1.48; trend test 0.003) and risk of type 2 diabetes (HR 1.24; 95% CI 1.11-1.38; trend test 0.002) showed significant association as well. Decreasing red-meat consumption would lead to reduce GHG emissions from diet and would reduce risk of mortality, coronary heart disease and type 2 diabetes.

BackgroundMost studies of the climate footprint of diets have been conducted in countries in the global north, but the majority of the world population lives in global south countries. We estimated total dietary greenhouse gas emissions (GHGE) in Mexico, examined the contribution of major food and beverage groups, and assessed variation across social groups.MethodsWe linked individual-level dietary data from the Mexican National Health and Nutrition Survey 2018 to the SHARP Indicators Database, containing GHGE estimates for 182 primary food and beverages.ResultsMean dietary GHGE was 3.9 kg of carbon dioxide equivalent per person per day. Dietary GHGE is highest among those in young adulthood and middle age versus adolescents and older adults, and among males, those with higher educational attainment, higher socioeconomic status, that do not speak an indigenous language, and that live in urban areas.ConclusionThe Mexican diet has a much lower carbon footprint than diets in other Latin American countries for which such estimates are available. In contrast to patterns observed in Argentina and Brazil, dietary GHGE was lowest in those in lower socioeconomic and educational strata and in rural areas. A better understanding of the differences in diet sustainability between and within countries will be needed for developing global and local strategies that meet the environmental sustainability goals.

Planetary Health Diet Index Trends and Associations with Dietary Greenhouse Gas Emissions, Disease Biomarkers, Obesity, and Mortality in the United States (2005-2018).

Diets have been changing drastically in China in the recent decades and this change has contributed considerably to greenhouse gas (GHG) emissions. In determining effective mitigation strategies for future emissions, it is necessary to know how emissions related to diet vary over time in overall magnitude and due to compositional changes driven by socioeconomic dynamics. This study evaluates the change in dietary GHG emissions in China during the 1997–2011 period by linking environmentally extended input–output tables with individual daily food intake data. It further decomposes the contribution to GHG emission changes of various socioeconomic driving factors. The results show that GHG emissions related to national diet have been decreasing from 1,180 Mt CO 2 e to 640 Mt CO 2 e (a 54% decline), largely due to technical innovation that has reduced the emissions per calorie of food (135% of the total reduction). The change in dietary patterns has had mixed effects, with a decline in calorie intake reducing emissions by 21% while increases in animal‐sourced food consumption have raised emissions by 25%. Our findings stress the importance of technical progress in the historical change in dietary GHG emissions and suggest a focus on behavior changes for future research and policymaking, which has the potential to promote dietary changes toward less animal product consumption. Our findings highlight the importance of both technological and demand‐side behavioral options in reducing the impact of diets on GHG emissions.

BackgroundHuman diets account for 30% of greenhouse gas emissions (GHGE). Reporting dietary GHGE with or without energy standardization yields different outcomes, often resulting in conflicting conclusions regarding associations with micronutrient intake.ObjectivesThis study aims to compare methods of reporting dietary GHGE, with and without consideration of energy intake, and their respective associations with micronutrient intake.MethodsData were sourced from the Malmö Diet and Cancer Study, a cohort involving 25,970 participants. GHGE were estimated based on life cycle assessment data. The study explores different methods of reporting dietary climate impact: GHGE per day, GHGE per 1000 kcal, and with different energy adjustments. Association with micronutrient intake was modeled as daily intake and per 1000 kcal using linear regression models.ResultsDiets with higher GHGE per day were associated with a higher daily intake of all 17 examined micronutrients. When energy was included in the model, the results for GHGE per 1000 kcal aligned well with those for GHGE per day. However, using GHGE per 1000 kcal generally showed that higher GHGE were linked to lower daily micronutrient intake. Different methods of adjusting for energy intake yielded estimates with varying directions and magnitudes of associations.ConclusionsThis study highlights the implications of energy intake when assessing the impact of dietary GHGE and demonstrates that the choice of GHGE modeling approach might have important consequences for the results and interpretation. The method of choice for modeling dietary GHGE in relation to micronutrient intake needs to be carefully considered in future studies.

Objectives: This study’s main objective was to examine the association between dietary greenhouse gas emissions (GHGEs) and diet quality among U.S. primary and secondary schoolchildren. Our secondary objectives were to identify demographic characteristics associated with higher-GHGE diets and to assess the relationship between school meal consumption and dietary GHGE. Methods: We conducted a cross-sectional secondary analysis of dietary intake data from 2165 primary and secondary students participating in the nationally representative 2014–2015 US School Nutrition and Meal Cost Study (SNMCS). Dietary GHGEs (kg CO2-equivalents per 1000 kcal) were estimated by linking reported foods to an environmental impact database. Diet quality was assessed using the Healthy Eating Index-2010 (HEI). Students were categorized into GHGE groups, and differences in total HEI and component scores were examined using appropriate statistical tests. Statistical significance was set at p < 0.05. Results: The average dietary GHGE of the sample was 3.64 kg CO2-equivalent per person per day. Overall, HEI scores did not differ between the GHGE groups (p = 0.22). However, compared to the high-GHGE group, the low-GHGE group scored significantly higher on some HEI-2010 components, such as fatty acid ratios (p < 0.0001) and sodium (p < 0.0001), and significantly lower on others, such as dairy (p < 0.0001), total protein foods (p < 0.0001), and refined grains (p < 0.0001). Male students and students who ate school meals on the day of recall had higher odds of being in the high-GHGE group compared with their respective reference groups. Conclusions: Lower dietary carbon footprints are achievable without sacrificing overall diet quality, but tradeoffs in specific dietary components indicate the need for additional research and care in recommending diet changes or setting school policies.

Shifting consumer behavior towards more sustainable diets can benefit environmental sustainability and human health. Although more frequent home cooking is associated with a better diet quality and fast-food consumption with worse diet quality, the environmental impact of diets based on frequency of cooking or eating fast food is not well understood. The objective of this study was to investigate whether the frequency of cooking dinner at home or eating fast food is associated with dietary greenhouse gas emissions (GHGE). We linked 24-h dietary recall data from adult respondents in the 2007–2010 National Health and Nutrition Examination Survey (NHANES) (N = 11,469) to a database of GHGE factors to obtain a measure of dietary GHGE (kgCO2-eq/2000 kcal) (the sum of emissions released in the production of food for an individual’s diet), adjusted by energy intake (kgCO2-eq/2000 kcal). We examined associations between frequency of cooking dinner (the only meal for which cooking frequency was measured), frequency of eating fast food, and dietary GHGE and protein sources (beef, pork, poultry, other meat, and fish and seafood (g/2000 kcal)) using generalized linearized regression models that controlled for age, sex, and other socio-economic characteristics. Greater cooking frequency was associated with higher dietary GHGE. In fully adjusted models, cooking 5–6 times/week was associated with an additional 0.058 kgCO2-eq/2000 kcal (SE 0.033) and cooking 7 times/week was associated with an additional 0.057 kgCO2-eq/2000 kcal (SE 0.027) when compared to cooking 0–2 times/week. Individuals in households who cooked dinner more frequently consumed significantly more meat, poultry, and fish (cooking 7 times/week: 148.7 g/2000 kcal vs. cooking 0–2 times/week: 135.4 g/2000 kcal, p-trend = 0.005), which could explain the association with a higher carbon footprint diet. There were few associations of note between fast-food frequency and GHGE. Policies and interventions that reduce consumption of meat and increase consumption of plants when both cooking meals at home and eating meals out are needed to shift toward diets that will be beneficial for both human health and the health of the planet.