Impacts of home cooking methods and appliances on the GHG emissions of food

GHG mitigation strategies on China's diverse dish consumption are key to meet the Paris Agreement targets

Combatting climate change depends on demand-side mitigation strategies related to food, which is in turn contingent on explicit estimation and management of dish-level emissions. Here, on the basis of a bottom-up integrated emissions framework, we first estimate the greenhouse gas emissions of 540 dishes from 36 cuisines using data from over 800,488 restaurants in China's provincial capital cities. By mining residents' dietary preferences, we then design various dietary change strategies to explicitly link food emissions to the Paris Agreement pledges. The results show that China's food system greenhouse gas emissions were approximately 4.64 GtCO2eq in 2020, accounting for 37% of total emissions, with average per-dish emissions of 8.44 kgCO2eq. Current emission patterns of food consumption in China may not be consistent with the attainment of the 1.5 °C and 2 °C climate targets, but transitioning towards low-emission cuisines and dishes could change that by reducing emissions by 38-69%.

Mixed diets can meet nutrient requirements with lower carbon footprints

Achieving sustainable dietary change is essential for safeguarding human and environmental health. However, dietary recommendations based on broad food groups may not accurately reflect real-world realities because individuals select and consume dishes with multiple food items influenced by diverse context-specific factors. Therefore, here we explored the sustainability trade-offs of dietary choices at the dish level through an optimization modeling approach tested in Japan. We estimated the nutritional quality, price, and carbon footprint of major Japanese dishes and examined 16 dietary scenarios to identify options that meet the nutritional requirements and minimize carbon footprint. Overall, mixed diets contain more combinations of dishes that meet nutritional requirements with lower carbon footprints compared to more restrictive dietary scenarios. We argue that the approach developed here enables a better understanding of dietary trade-offs, complements existing methods, and helps identify sustainable diets by offering nuanced information at the national and sub-national levels.

The environmental impact of beef and ultra-processed food consumption in Brazil

OBJECTIVE

This study evaluated the independent and combined environmental impacts of the consumption of beef and ultra-processed foods in Brazil.

DESIGN

Cross-sectional study.

SETTING

Brazil.

PARTICIPANTS

We used food purchases data from a national household budget survey conducted between July 2017 and July 2018, representing all Brazilian households. Food purchases were converted into energy, carbon footprints and water footprints. Multiple linear regression models were used to assess the association between quintiles of beef and ultra-processed foods in total energy purchases and the environmental footprints, controlling for sociodemographic variables.

RESULTS

Both beef and ultra-processed foods had a significant linear association with carbon and water footprints (P < 0·01) in crude and adjusted models. In the crude upper quintile of beef purchases, carbon and water footprints were 47·7 % and 30·8 % higher, respectively, compared to the lower quintile. The upper quintile of ultra-processed food purchases showed carbon and water footprints 14·4 % and 22·8 % higher, respectively, than the lower quintile. The greatest reduction in environmental footprints would occur when both beef and ultra-processed food purchases are decreased, resulting in a 21·1 % reduction in carbon footprint and a 20·0 % reduction in water footprint.

CONCLUSIONS

Although the environmental footprints associated with beef consumption are higher, dietary patterns with lower consumption of beef and ultra-processed foods combined showed the greatest reduction in carbon and water footprints in Brazil. The high consumption of beef and ultra-processed foods is harmful to human health, as well as to the environment; thus, their reduction is beneficial to both.

Ready meals, especially those that are animal-based and cooked in an oven, have lower nutritional quality and higher greenhouse gas emissions and are more expensive than equivalent home-cooked meals

OBJECTIVE

To examine whether ready meals and equivalent home-cooked meals differ in nutritional quality indicators, greenhouse gas emissions (GHGE) and cost.

DESIGN

We performed a cross-sectional analysis of meal data from the National Diet and Nutrition Survey (NDNS) nutrient databank (2018/19). Additional data on nutrient composition, cost and cooking-related GHGE were calculated and compared between fifty-four ready meals and equivalent home-cooked meals.

SETTING

The UK.

PARTICIPANTS

Not applicable.

RESULTS

Ready meals, overall and those that were animal-based, had significantly higher levels of free sugar compared with equivalent home-cooked meals (P < 0·0001 and P < 0·0004, respectively). Animal-based ready meals had significantly higher levels of GHGE (P < 0·001), whereas the cost of ready meals, overall, was significantly higher (P < 0·001), compared with equivalent home-cooked meals. Animal-based meals, whether ready meals or equivalent homemade meals, had significantly higher levels of protein (P < 0·0001), contained significantly more kilocalories (P = 0·001), had significantly higher levels of GHGE (P < 0·0001) and were significantly more expensive (P < 0·0001), compared with plant-based meals. Overall, plant-based meals home-cooked on the gas or electric stove had the lowest GHGE and cost, whereas animal-based oven-cooked ready meals had the highest levels of GHGE and were most expensive.

CONCLUSIONS

Ready meals have lower nutritional quality and higher GHGE and are more expensive than equivalent home-cooked meals, especially those meals that are animal-based and prepared in an oven.

Food Banks against Climate Change, a Solution That Works: A Case Study in Navarra, Spain

Worldwide, more than 1.3 billion tonnes of food are wasted each year, which is equivalent to releasing 4.4 Gt of CO₂ equivalents (CO₂e). In this context, the Food Bank of Navarra (FBN) annually avoids the waste of approximately 3000 tons of perfectly consumable food. The aim of this study was twofold: on the one hand, to analyse the carbon footprint of the FBN and, on the other hand, to perform a comparative analysis of the greenhouse gas (GHG) emissions in two scenarios, "with" and "without" the actions of the FBN, in order to identify and quantify the environmental benefits, in terms of GHG emissions reduction, associated with the reduction in food waste. The analyses were conducted in two different years. The carbon footprint associated with the FBN's activities was 147 t of CO₂e in the year 2018. The quantification of GHGs in the scenario "without the FBN" showed that if the FBN did not exist 4715 t of CO₂e would have been emitted. The results obtained in consecutive years were similar, highlighting the importance of the FBN-not only in social terms but also environmental terms-as it prevented a large amount of GHGs from being emitted into the atmosphere. A detailed account of the carbon emission reduction associated with the food bank's operations and the knowledge of the benefits involved could boost their positive effects in facilitating the integration of their activities into policies aimed at climate neutrality.

Climate Change and Six Americas: What Can Behavior Analysts Do?

Climate change, directly impacted by human behavior, has been investigated and evaluated across disciplines. The Six Americas was developed as a segmentation tool to communicate effectively with the United States population about climate change (Leiserowitz et al., 2021) across a spectrum from those likely to act in opposition to climate change mitigation strategies to those actively seeking to remediate the climate change effects. Behavior analysts offer unique skills to intervene at the individual level effectively. Behavior analysts will benefit from learning about this conceptual model and its tools, particularly to inform intervention across the spectrum of the Six Americas. This paper will cover a background of the Six Americas and suggestions on how to intervene for these different segments at the individual level, followed by a brief review of the existing effective literature, particularly regarding changing behavior in the food, energy, and transportation sectors. Specifically, behavior analytic interventions will be suggested for a population concerned about climate change who may also be posed for action. Finally, we will provide suggestions to guide behavior analysts to intervene with those disengaged or actively dismissive of the threats posed by climate change.

The (scarce and circumscribed) culinary content in food-based dietary guidelines around the world: 1991-2021

OBJECTIVE

To evaluate the culinary content of key messages contained in food-based dietary guidelines (FBDG) available at the global online repository of the FAO of the UN.

DESIGN

Document analysis was conducted in August 2021 with data extraction of key messages explicitly related to cooking present in FBDG. Data were analysed inductively using thematic analysis.

SETTING

The FAO's global repository of FBDG.

PARTICIPANTS

Not applicable.

RESULTS

Just over half (n 39; 53·4 %) of the seventy-three FBDG analysed included at least one key message about cooking. The Latin American and Caribbean FBDG presented the greatest amount and variety of content about cooking in the key messages, whereas the Near East and North America placed less emphasis on cooking. We identified three themes: (i) healthy food preparation (n 35; 61·4 % of the fifty-seven culinary key messages identified); (ii) food hygiene (n 14; 24·6 %) and (iii) the promotion of culinary practices (n 7; 12·3 %). Albania's key message covered two themes (food hygiene and healthy food preparation) (n 1; 1·8 %).

CONCLUSION

FBDG are official documents that express recommendations for a healthy diet. As most of these recommendations throughout the world include foods that must be cooked prior to consumption, culinary content should gain more visibility and be presented more broadly in these official documents.

Food-Level Analysis to Identify Dietary Choices With the Highest Nutritional Quality and Lowest Greenhouse Gas Emissions and Price

Introduction

Food systems are challenged to provide healthy, sustainable and affordable foods. From a consumer perspective, identifying healthy, sustainable and affordable choices based on individual food products rather than diets could promote better shopping choices.

Objective

To identify foods and drinks with the highest nutritional quality and lowest greenhouse gas emissions (GHGE) and price. We also assessed how a combination of these indicators (e.g., nutritional quality, GHGE and price) for food categories aligned with current United Kingdom dietary recommendations.

Materials and Methods

We performed a secondary analysis of the National Diet and Nutrition Survey (NDNS) nutrient databank year 11 (2018/2019). Spearman correlation coefficients were used to assess the strength of relationships between nutritional quality, environmental impact and/or prices per 100 kcal. In addition, we developed an optimized nutritional quality, GHGE and price score for each food or drink item based on the overall medians for each of these indicators.

Results

Median nutritional value was highest for fruit and vegetables, whilst median GHGE and price was lower for starchy carbohydrates, fats and items of which consumption should be limited. The relative proportions of foods considered the most nutritious and with a low GHGE and price in each of the food categories, on a per 100 kcal basis, were comparable to the proportions in the Eatwell Guide, except for the proportion of fruits and vegetables being smaller and the proportion of potatoes, bread, rice, pasta, and other starchy carbohydrates being larger in our analysis.

Conclusion

Public health efforts should consider the impact of dietary choices not only in terms of nutritional quality but also in terms of environmental and economic impact. Our food-based analysis shows a large variation in nutritional quality, GHGE and price within and across food categories, which provides consumers with opportunities for “food swaps” that are more nutritious and have lower GHGE and price.

Nutritional Quality, Environmental Impact and Cost of Ultra-Processed Foods: A UK Food-Based Analysis

Food-based analyses of the healthiness, environmental sustainability and affordability of processed and ultra-processed foods are lacking. This paper aimed to determine how ultra-processed and processed foods compare to fresh and minimally processed foods in relation to nutritional quality, greenhouse gas emissions and cost on the food and food group level. Data from the National Diet and Nutrition Survey nutrient databank year 11 (2018/2019) were used for this analysis. Median and bootstrapped medians of nutritional quality (NRF8.3 index), greenhouse gas emissions (gCO2-equivalents) and cost (in GBP) were compared across processing categories. An optimal score based on the medians was created to identify the most nutritional, sustainable, and affordable options across processing categories. On a per 100 kcal basis, ultra-processed and processed foods had a lower nutritional quality, lower greenhouse gas emissions, and were cheaper than minimally processed foods, regardless of their total fat, salt and/or sugar content. The most nutritious, environmentally friendly, and affordable foods were generally lower in total fat, salt, and sugar, irrespective of processing level. The high variability in greenhouse gas emissions and cost across food groups and processing levels offer opportunities for food swaps representing the healthiest, greenest, and most affordable options.

Cooking at Home, Fast Food, Meat Consumption, and Dietary Carbon Footprint among US Adults

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.

Recommendations for Integrating Evidence-Based, Sustainable Diet Information into Nutrition Education

The adoption of more sustainable diets (SD) has the capacity to meet the needs of individuals without compromising future generations' abilities to do the same. Nutrition educators are ideal candidates for delivering SD education to consumers, yet evidence-based recommendations for the profession have not been crafted. The results of a thorough, narrative review of the literature performed in 2021 suggest there are five well-supported recommendations nutrition educators should consider incorporating in their work. They are (1) shift towards a plant-based diet, (2) mitigate food waste, (3) limit consumption of ultra-processed foods (UPF), (4) engage in local food systems, and (5) choose sustainable seafood. Each recommendation is discussed below in detail, to provide nutrition educators with a nuanced scope of the issue, after which suggestions for the inclusion of these recommendations, using an example of the authors' experiences from the US Expanded Food and Nutrition Education Program (EFNEP), are provided.

Greenhouse gas emissions, water footprint, and ecological footprint of food purchases according to their degree of processing in Brazilian metropolitan areas: a time-series study from 1987 to 2018

BACKGROUND

The consumption of ultra-processed foods has increased worldwide and has been related to the occurrence of obesity and other non-communicable diseases. However, little is known about the environmental effects of ultra-processed foods. We aimed to assess the temporal trends in greenhouse gas emissions (GHGE), water footprint, and ecological footprint of food purchases in Brazilian metropolitan areas, and how these are affected by the amount of food processing.

METHODS

In this time-series study, we used data from five Brazilian Household Budget Surveys (1987-88, 1995-96, 2002-03, 2008-09, 2017-18) to calculate GHGE, water footprint, and ecological footprint per 1000 kcal of food and beverages purchased. Food items were classified into NOVA food groups: unprocessed or minimally processed foods (G1); processed culinary ingredients (G2); processed foods (G3); and ultra-processed foods (G4). We calculated the proportion each NOVA food group contributes to daily kcal per person. Linear regression was performed to evaluate trends of the environmental impacts across the years.

FINDINGS

Between 1987-88 and 2017-18, diet-related GHGE increased by 21% (from 1538·6 g CO₂ equivalent [CO₂e] per 1000 kcal [95% CI 1473·3-1604·0] to 1866·0 g CO₂e per 1000 kcal [1788·0-1944·0]; p_trend<0·0001), diet-related water footprint increased by 22% (from 1447·2 L/1000 kcal [95% CI 1400·7-1493·8] to 1769·1 L/1000 kcal [1714·5-1823·7]; p_trend<0·0001), and diet-related ecological footprint increased by 17% (from 9·69 m²/1000 kcal [95% CI 9·33-10·05] to 11·36 m²/1000 kcal [10·91-11·81]; p_trend<0·0001). We found that the change in the environmental indicators over time varied between NOVA food groups. We did not find evidence of a change in the environmental indicators for G1 foods over time. GHGE from G2 foods decreased by 18% (p_trend<0·0001), whereas GHGE from G4 foods increased by 245% (p_trend<0·0001). The water footprint from G2 foods decreased by 17% (p_trend<0·0001) whereas the water footprint from G4 foods increased by 233% (p_trend<0·0001). The ecological footprint from G2 foods decreased by 13% (p_trend<0·0001), whereas the ecological footprint from G3 foods increased by 49% (p_trend<0·0001) and from G4 foods increased by 183% (p_trend<0·0001). We found no significant change in contribution by any other NOVA food groups to any of the three environmental indicators over the study period.

INTERPRETATION

The environmental effects of the Brazilian diet have increased over the past three decades along with increased effects from ultra-processed foods. This means that dietary patterns in Brazil are becoming potentially more harmful to human and planetary health. Therefore, a shift in the current trend would be needed to enhance sustainable healthy food systems.

FUNDING

Science and Technologies Facilities Council-Global Challenges Research Fund.